diff --git a/src/rinterface.c b/src/rinterface.c
index 1dbee45eaf..2aefc203b2 100644
--- a/src/rinterface.c
+++ b/src/rinterface.c
@@ -141,8 +141,22 @@ SEXP R_igraph_empty(SEXP n, SEXP directed) {
 
   SEXP r_result;
                                         /* Convert input */
-  c_n=(igraph_integer_t) REAL(n)[0];
-  c_directed=LOGICAL(directed)[0];
+  if (Rf_xlength(n) == 1) {
+    if (((igraph_integer_t) REAL(n)[0]) != REAL(n)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(n)[0]);
+    }
+    c_n = (igraph_integer_t) REAL(n)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(n));
+  }
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_empty(&c_graph, c_n, c_directed));
 
@@ -274,8 +288,22 @@ SEXP R_igraph_empty_attrs(SEXP n, SEXP directed) {
 
   SEXP r_result;
                                         /* Convert input */
-  c_n=(igraph_integer_t) REAL(n)[0];
-  c_directed=LOGICAL(directed)[0];
+  if (Rf_xlength(n) == 1) {
+    if (((igraph_integer_t) REAL(n)[0]) != REAL(n)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(n)[0]);
+    }
+    c_n = (igraph_integer_t) REAL(n)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(n));
+  }
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_empty_attrs(&c_graph, c_n, c_directed, 0));
 
@@ -311,7 +339,12 @@ SEXP R_igraph_get_all_eids_between(SEXP graph, SEXP from, SEXP to, SEXP directed
   IGRAPH_FINALLY(igraph_vector_int_destroy, &c_eids);
   c_from = (igraph_integer_t) REAL(from)[0];
   c_to = (igraph_integer_t) REAL(to)[0];
-  c_directed=LOGICAL(directed)[0];
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_get_all_eids_between(&c_graph, &c_eids, c_from, c_to, c_directed));
 
@@ -507,9 +540,27 @@ SEXP R_igraph_wheel(SEXP n, SEXP mode, SEXP center) {
 
   SEXP r_result;
                                         /* Convert input */
-  c_n=(igraph_integer_t) REAL(n)[0];
+  if (Rf_xlength(n) == 1) {
+    if (((igraph_integer_t) REAL(n)[0]) != REAL(n)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(n)[0]);
+    }
+    c_n = (igraph_integer_t) REAL(n)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(n));
+  }
   c_mode = (igraph_wheel_mode_t) Rf_asInteger(mode);
-  c_center=(igraph_integer_t) REAL(center)[0];
+  if (Rf_xlength(center) == 1) {
+    if (((igraph_integer_t) REAL(center)[0]) != REAL(center)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(center)[0]);
+    }
+    c_center = (igraph_integer_t) REAL(center)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(center));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_wheel(&c_graph, c_n, c_mode, c_center));
 
@@ -541,9 +592,28 @@ SEXP R_igraph_square_lattice(SEXP dimvector, SEXP nei, SEXP directed, SEXP mutua
                                         /* Convert input */
   R_SEXP_to_vector_int_copy(dimvector, &c_dimvector);
   IGRAPH_FINALLY(igraph_vector_int_destroy, &c_dimvector);
-  c_nei=(igraph_integer_t) REAL(nei)[0];
-  c_directed=LOGICAL(directed)[0];
-  c_mutual=LOGICAL(mutual)[0];
+  if (Rf_xlength(nei) == 1) {
+    if (((igraph_integer_t) REAL(nei)[0]) != REAL(nei)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(nei)[0]);
+    }
+    c_nei = (igraph_integer_t) REAL(nei)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(nei));
+  }
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
+  if (Rf_xlength(mutual) == 1) {
+    c_mutual = LOGICAL(mutual)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(mutual));
+  }
   if (!Rf_isNull(periodic)) {
     R_SEXP_to_vector_bool(periodic, &c_periodic);
   }
@@ -578,8 +648,18 @@ SEXP R_igraph_triangular_lattice(SEXP dimvector, SEXP directed, SEXP mutual) {
                                         /* Convert input */
   R_SEXP_to_vector_int_copy(dimvector, &c_dimvector);
   IGRAPH_FINALLY(igraph_vector_int_destroy, &c_dimvector);
-  c_directed=LOGICAL(directed)[0];
-  c_mutual=LOGICAL(mutual)[0];
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
+  if (Rf_xlength(mutual) == 1) {
+    c_mutual = LOGICAL(mutual)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(mutual));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_triangular_lattice(&c_graph, &c_dimvector, c_directed, c_mutual));
 
@@ -640,8 +720,26 @@ SEXP R_igraph_regular_tree(SEXP h, SEXP k, SEXP type) {
 
   SEXP r_result;
                                         /* Convert input */
-  c_h=(igraph_integer_t) REAL(h)[0];
-  c_k=(igraph_integer_t) REAL(k)[0];
+  if (Rf_xlength(h) == 1) {
+    if (((igraph_integer_t) REAL(h)[0]) != REAL(h)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(h)[0]);
+    }
+    c_h = (igraph_integer_t) REAL(h)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(h));
+  }
+  if (Rf_xlength(k) == 1) {
+    if (((igraph_integer_t) REAL(k)[0]) != REAL(k)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(k)[0]);
+    }
+    c_k = (igraph_integer_t) REAL(k)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(k));
+  }
   c_type = (igraph_tree_mode_t) Rf_asInteger(type);
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_regular_tree(&c_graph, c_h, c_k, c_type));
@@ -669,8 +767,22 @@ SEXP R_igraph_full_citation(SEXP n, SEXP directed) {
 
   SEXP r_result;
                                         /* Convert input */
-  c_n=(igraph_integer_t) REAL(n)[0];
-  c_directed=LOGICAL(directed)[0];
+  if (Rf_xlength(n) == 1) {
+    if (((igraph_integer_t) REAL(n)[0]) != REAL(n)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(n)[0]);
+    }
+    c_n = (igraph_integer_t) REAL(n)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(n));
+  }
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_full_citation(&c_graph, c_n, c_directed));
 
@@ -698,10 +810,24 @@ SEXP R_igraph_extended_chordal_ring(SEXP nodes, SEXP W, SEXP directed) {
 
   SEXP r_result;
                                         /* Convert input */
-  c_nodes=(igraph_integer_t) REAL(nodes)[0];
+  if (Rf_xlength(nodes) == 1) {
+    if (((igraph_integer_t) REAL(nodes)[0]) != REAL(nodes)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(nodes)[0]);
+    }
+    c_nodes = (igraph_integer_t) REAL(nodes)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(nodes));
+  }
   R_SEXP_to_matrix_int(W, &c_W);
   IGRAPH_FINALLY(igraph_matrix_int_destroy, &c_W);
-  c_directed=LOGICAL(directed)[0];
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_extended_chordal_ring(&c_graph, c_nodes, &c_W, c_directed));
 
@@ -732,8 +858,22 @@ SEXP R_igraph_graph_power(SEXP graph, SEXP order, SEXP directed) {
   SEXP r_result;
                                         /* Convert input */
   R_SEXP_to_igraph(graph, &c_graph);
-  c_order=(igraph_integer_t) REAL(order)[0];
-  c_directed=LOGICAL(directed)[0];
+  if (Rf_xlength(order) == 1) {
+    if (((igraph_integer_t) REAL(order)[0]) != REAL(order)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(order)[0]);
+    }
+    c_order = (igraph_integer_t) REAL(order)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(order));
+  }
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_graph_power(&c_graph, &c_res, c_order, c_directed));
 
@@ -761,10 +901,28 @@ SEXP R_igraph_lcf_vector(SEXP n, SEXP shifts, SEXP repeats) {
 
   SEXP r_result;
                                         /* Convert input */
-  c_n=(igraph_integer_t) REAL(n)[0];
+  if (Rf_xlength(n) == 1) {
+    if (((igraph_integer_t) REAL(n)[0]) != REAL(n)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(n)[0]);
+    }
+    c_n = (igraph_integer_t) REAL(n)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(n));
+  }
   R_SEXP_to_vector_int_copy(shifts, &c_shifts);
   IGRAPH_FINALLY(igraph_vector_int_destroy, &c_shifts);
-  c_repeats=(igraph_integer_t) REAL(repeats)[0];
+  if (Rf_xlength(repeats) == 1) {
+    if (((igraph_integer_t) REAL(repeats)[0]) != REAL(repeats)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(repeats)[0]);
+    }
+    c_repeats = (igraph_integer_t) REAL(repeats)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(repeats));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_lcf_vector(&c_graph, c_n, &c_shifts, c_repeats));
 
@@ -798,7 +956,12 @@ SEXP R_igraph_adjlist(SEXP adjlist, SEXP mode, SEXP duplicate) {
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
   c_mode = (igraph_neimode_t) Rf_asInteger(mode);
-  c_duplicate=LOGICAL(duplicate)[0];
+  if (Rf_xlength(duplicate) == 1) {
+    c_duplicate = LOGICAL(duplicate)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(duplicate));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_adjlist(&c_graph, &c_adjlist, c_mode, c_duplicate));
 
@@ -834,9 +997,32 @@ SEXP R_igraph_full_bipartite(SEXP n1, SEXP n2, SEXP directed, SEXP mode) {
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
   IGRAPH_FINALLY(igraph_vector_bool_destroy, &c_types);
-  c_n1=(igraph_integer_t) REAL(n1)[0];
-  c_n2=(igraph_integer_t) REAL(n2)[0];
-  c_directed=LOGICAL(directed)[0];
+  if (Rf_xlength(n1) == 1) {
+    if (((igraph_integer_t) REAL(n1)[0]) != REAL(n1)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(n1)[0]);
+    }
+    c_n1 = (igraph_integer_t) REAL(n1)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(n1));
+  }
+  if (Rf_xlength(n2) == 1) {
+    if (((igraph_integer_t) REAL(n2)[0]) != REAL(n2)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(n2)[0]);
+    }
+    c_n2 = (igraph_integer_t) REAL(n2)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(n2));
+  }
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
   c_mode = (igraph_neimode_t) Rf_asInteger(mode);
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_full_bipartite(&c_graph, &c_types, c_n1, c_n2, c_directed, c_mode));
@@ -883,7 +1069,12 @@ SEXP R_igraph_full_multipartite(SEXP n, SEXP directed, SEXP mode) {
   IGRAPH_FINALLY(igraph_vector_int_destroy, &c_types);
   R_SEXP_to_vector_int_copy(n, &c_n);
   IGRAPH_FINALLY(igraph_vector_int_destroy, &c_n);
-  c_directed=LOGICAL(directed)[0];
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
   c_mode = (igraph_neimode_t) Rf_asInteger(mode);
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_full_multipartite(&c_graph, &c_types, &c_n, c_directed, c_mode));
@@ -967,10 +1158,24 @@ SEXP R_igraph_circulant(SEXP n, SEXP shifts, SEXP directed) {
 
   SEXP r_result;
                                         /* Convert input */
-  c_n=(igraph_integer_t) REAL(n)[0];
+  if (Rf_xlength(n) == 1) {
+    if (((igraph_integer_t) REAL(n)[0]) != REAL(n)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(n)[0]);
+    }
+    c_n = (igraph_integer_t) REAL(n)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(n));
+  }
   R_SEXP_to_vector_int_copy(shifts, &c_shifts);
   IGRAPH_FINALLY(igraph_vector_int_destroy, &c_shifts);
-  c_directed=LOGICAL(directed)[0];
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_circulant(&c_graph, c_n, &c_shifts, c_directed));
 
@@ -999,8 +1204,26 @@ SEXP R_igraph_generalized_petersen(SEXP n, SEXP k) {
 
   SEXP r_result;
                                         /* Convert input */
-  c_n=(igraph_integer_t) REAL(n)[0];
-  c_k=(igraph_integer_t) REAL(k)[0];
+  if (Rf_xlength(n) == 1) {
+    if (((igraph_integer_t) REAL(n)[0]) != REAL(n)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(n)[0]);
+    }
+    c_n = (igraph_integer_t) REAL(n)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(n));
+  }
+  if (Rf_xlength(k) == 1) {
+    if (((igraph_integer_t) REAL(k)[0]) != REAL(k)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(k)[0]);
+    }
+    c_k = (igraph_integer_t) REAL(k)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(k));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_generalized_petersen(&c_graph, c_n, c_k));
 
@@ -1033,8 +1256,26 @@ SEXP R_igraph_turan(SEXP n, SEXP r) {
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
   IGRAPH_FINALLY(igraph_vector_int_destroy, &c_types);
-  c_n=(igraph_integer_t) REAL(n)[0];
-  c_r=(igraph_integer_t) REAL(r)[0];
+  if (Rf_xlength(n) == 1) {
+    if (((igraph_integer_t) REAL(n)[0]) != REAL(n)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(n)[0]);
+    }
+    c_n = (igraph_integer_t) REAL(n)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(n));
+  }
+  if (Rf_xlength(r) == 1) {
+    if (((igraph_integer_t) REAL(r)[0]) != REAL(r)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(r)[0]);
+    }
+    c_r = (igraph_integer_t) REAL(r)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(r));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_turan(&c_graph, &c_types, c_n, c_r));
 
@@ -1074,8 +1315,18 @@ SEXP R_igraph_weighted_sparsemat(SEXP A, SEXP directed, SEXP attr, SEXP loops) {
   SEXP r_result;
                                         /* Convert input */
   R_SEXP_to_sparsemat(A, &c_A);
-  c_directed=LOGICAL(directed)[0];
-  c_loops=LOGICAL(loops)[0];
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
+  if (Rf_xlength(loops) == 1) {
+    c_loops = LOGICAL(loops)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(loops));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_weighted_sparsemat(&c_graph, &c_A, c_directed, c_attr, c_loops));
 
@@ -1109,17 +1360,50 @@ SEXP R_igraph_preference_game(SEXP nodes, SEXP types, SEXP type_dist, SEXP fixed
 
   SEXP r_result, r_names;
                                         /* Convert input */
-  c_nodes=(igraph_integer_t) REAL(nodes)[0];
-  c_types=(igraph_integer_t) REAL(types)[0];
+  if (Rf_xlength(nodes) == 1) {
+    if (((igraph_integer_t) REAL(nodes)[0]) != REAL(nodes)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(nodes)[0]);
+    }
+    c_nodes = (igraph_integer_t) REAL(nodes)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(nodes));
+  }
+  if (Rf_xlength(types) == 1) {
+    if (((igraph_integer_t) REAL(types)[0]) != REAL(types)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(types)[0]);
+    }
+    c_types = (igraph_integer_t) REAL(types)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(types));
+  }
   R_SEXP_to_vector(type_dist, &c_type_dist);
-  c_fixed_sizes=LOGICAL(fixed_sizes)[0];
+  if (Rf_xlength(fixed_sizes) == 1) {
+    c_fixed_sizes = LOGICAL(fixed_sizes)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(fixed_sizes));
+  }
   R_SEXP_to_matrix(pref_matrix, &c_pref_matrix);
   if (0 != igraph_vector_int_init(&c_node_type_vec, 0)) {
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
   IGRAPH_FINALLY(igraph_vector_int_destroy, &c_node_type_vec);
-  c_directed=LOGICAL(directed)[0];
-  c_loops=LOGICAL(loops)[0];
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
+  if (Rf_xlength(loops) == 1) {
+    c_loops = LOGICAL(loops)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(loops));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_preference_game(&c_graph, c_nodes, c_types, &c_type_dist, c_fixed_sizes, &c_pref_matrix, &c_node_type_vec, c_directed, c_loops));
 
@@ -1164,9 +1448,36 @@ SEXP R_igraph_asymmetric_preference_game(SEXP nodes, SEXP out_types, SEXP in_typ
 
   SEXP r_result, r_names;
                                         /* Convert input */
-  c_nodes=(igraph_integer_t) REAL(nodes)[0];
-  c_out_types=(igraph_integer_t) REAL(out_types)[0];
-  c_in_types=(igraph_integer_t) REAL(in_types)[0];
+  if (Rf_xlength(nodes) == 1) {
+    if (((igraph_integer_t) REAL(nodes)[0]) != REAL(nodes)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(nodes)[0]);
+    }
+    c_nodes = (igraph_integer_t) REAL(nodes)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(nodes));
+  }
+  if (Rf_xlength(out_types) == 1) {
+    if (((igraph_integer_t) REAL(out_types)[0]) != REAL(out_types)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(out_types)[0]);
+    }
+    c_out_types = (igraph_integer_t) REAL(out_types)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(out_types));
+  }
+  if (Rf_xlength(in_types) == 1) {
+    if (((igraph_integer_t) REAL(in_types)[0]) != REAL(in_types)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(in_types)[0]);
+    }
+    c_in_types = (igraph_integer_t) REAL(in_types)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(in_types));
+  }
   R_SEXP_to_matrix(type_dist_matrix, &c_type_dist_matrix);
   R_SEXP_to_matrix(pref_matrix, &c_pref_matrix);
   if (0 != igraph_vector_int_init(&c_node_type_out_vec, 0)) {
@@ -1177,7 +1488,12 @@ SEXP R_igraph_asymmetric_preference_game(SEXP nodes, SEXP out_types, SEXP in_typ
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
   IGRAPH_FINALLY(igraph_vector_int_destroy, &c_node_type_in_vec);
-  c_loops=LOGICAL(loops)[0];
+  if (Rf_xlength(loops) == 1) {
+    c_loops = LOGICAL(loops)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(loops));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_asymmetric_preference_game(&c_graph, c_nodes, c_out_types, c_in_types, &c_type_dist_matrix, &c_pref_matrix, &c_node_type_out_vec, &c_node_type_in_vec, c_loops));
 
@@ -1221,9 +1537,24 @@ SEXP R_igraph_rewire_edges(SEXP graph, SEXP prob, SEXP loops, SEXP multiple) {
                                         /* Convert input */
   R_SEXP_to_igraph_copy(graph, &c_graph);
   IGRAPH_FINALLY(igraph_destroy, &c_graph);
-  c_prob=REAL(prob)[0];
-  c_loops=LOGICAL(loops)[0];
-  c_multiple=LOGICAL(multiple)[0];
+  if (Rf_xlength(prob) == 1) {
+    c_prob = REAL(prob)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(prob));
+  }
+  if (Rf_xlength(loops) == 1) {
+    c_loops = LOGICAL(loops)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(loops));
+  }
+  if (Rf_xlength(multiple) == 1) {
+    c_multiple = LOGICAL(multiple)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(multiple));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_rewire_edges(&c_graph, c_prob, c_loops, c_multiple));
 
@@ -1251,8 +1582,18 @@ SEXP R_igraph_rewire_directed_edges(SEXP graph, SEXP prob, SEXP loops, SEXP mode
                                         /* Convert input */
   R_SEXP_to_igraph_copy(graph, &c_graph);
   IGRAPH_FINALLY(igraph_destroy, &c_graph);
-  c_prob=REAL(prob)[0];
-  c_loops=LOGICAL(loops)[0];
+  if (Rf_xlength(prob) == 1) {
+    c_prob = REAL(prob)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(prob));
+  }
+  if (Rf_xlength(loops) == 1) {
+    c_loops = LOGICAL(loops)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(loops));
+  }
   c_mode = (igraph_neimode_t) Rf_asInteger(mode);
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_rewire_directed_edges(&c_graph, c_prob, c_loops, c_mode));
@@ -1282,11 +1623,44 @@ SEXP R_igraph_forest_fire_game(SEXP nodes, SEXP fw_prob, SEXP bw_factor, SEXP am
 
   SEXP r_result;
                                         /* Convert input */
-  c_nodes=(igraph_integer_t) REAL(nodes)[0];
-  c_fw_prob=REAL(fw_prob)[0];
-  c_bw_factor=REAL(bw_factor)[0];
-  c_ambs=(igraph_integer_t) REAL(ambs)[0];
-  c_directed=LOGICAL(directed)[0];
+  if (Rf_xlength(nodes) == 1) {
+    if (((igraph_integer_t) REAL(nodes)[0]) != REAL(nodes)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(nodes)[0]);
+    }
+    c_nodes = (igraph_integer_t) REAL(nodes)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(nodes));
+  }
+  if (Rf_xlength(fw_prob) == 1) {
+    c_fw_prob = REAL(fw_prob)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(fw_prob));
+  }
+  if (Rf_xlength(bw_factor) == 1) {
+    c_bw_factor = REAL(bw_factor)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(bw_factor));
+  }
+  if (Rf_xlength(ambs) == 1) {
+    if (((igraph_integer_t) REAL(ambs)[0]) != REAL(ambs)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(ambs)[0]);
+    }
+    c_ambs = (igraph_integer_t) REAL(ambs)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(ambs));
+  }
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_forest_fire_game(&c_graph, c_nodes, c_fw_prob, c_bw_factor, c_ambs, c_directed));
 
@@ -1316,13 +1690,32 @@ SEXP R_igraph_static_fitness_game(SEXP no_of_edges, SEXP fitness_out, SEXP fitne
 
   SEXP r_result;
                                         /* Convert input */
-  c_no_of_edges=(igraph_integer_t) REAL(no_of_edges)[0];
+  if (Rf_xlength(no_of_edges) == 1) {
+    if (((igraph_integer_t) REAL(no_of_edges)[0]) != REAL(no_of_edges)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(no_of_edges)[0]);
+    }
+    c_no_of_edges = (igraph_integer_t) REAL(no_of_edges)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(no_of_edges));
+  }
   R_SEXP_to_vector(fitness_out, &c_fitness_out);
   if (!Rf_isNull(fitness_in)) {
     R_SEXP_to_vector(fitness_in, &c_fitness_in);
   }
-  c_loops=LOGICAL(loops)[0];
-  c_multiple=LOGICAL(multiple)[0];
+  if (Rf_xlength(loops) == 1) {
+    c_loops = LOGICAL(loops)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(loops));
+  }
+  if (Rf_xlength(multiple) == 1) {
+    c_multiple = LOGICAL(multiple)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(multiple));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_static_fitness_game(&c_graph, c_no_of_edges, &c_fitness_out, (Rf_isNull(fitness_in) ? 0 : &c_fitness_in), c_loops, c_multiple));
 
@@ -1354,13 +1747,56 @@ SEXP R_igraph_static_power_law_game(SEXP no_of_nodes, SEXP no_of_edges, SEXP exp
 
   SEXP r_result;
                                         /* Convert input */
-  c_no_of_nodes=(igraph_integer_t) REAL(no_of_nodes)[0];
-  c_no_of_edges=(igraph_integer_t) REAL(no_of_edges)[0];
-  c_exponent_out=REAL(exponent_out)[0];
-  c_exponent_in=REAL(exponent_in)[0];
-  c_loops=LOGICAL(loops)[0];
-  c_multiple=LOGICAL(multiple)[0];
-  c_finite_size_correction=LOGICAL(finite_size_correction)[0];
+  if (Rf_xlength(no_of_nodes) == 1) {
+    if (((igraph_integer_t) REAL(no_of_nodes)[0]) != REAL(no_of_nodes)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(no_of_nodes)[0]);
+    }
+    c_no_of_nodes = (igraph_integer_t) REAL(no_of_nodes)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(no_of_nodes));
+  }
+  if (Rf_xlength(no_of_edges) == 1) {
+    if (((igraph_integer_t) REAL(no_of_edges)[0]) != REAL(no_of_edges)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(no_of_edges)[0]);
+    }
+    c_no_of_edges = (igraph_integer_t) REAL(no_of_edges)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(no_of_edges));
+  }
+  if (Rf_xlength(exponent_out) == 1) {
+    c_exponent_out = REAL(exponent_out)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(exponent_out));
+  }
+  if (Rf_xlength(exponent_in) == 1) {
+    c_exponent_in = REAL(exponent_in)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(exponent_in));
+  }
+  if (Rf_xlength(loops) == 1) {
+    c_loops = LOGICAL(loops)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(loops));
+  }
+  if (Rf_xlength(multiple) == 1) {
+    c_multiple = LOGICAL(multiple)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(multiple));
+  }
+  if (Rf_xlength(finite_size_correction) == 1) {
+    c_finite_size_correction = LOGICAL(finite_size_correction)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(finite_size_correction));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_static_power_law_game(&c_graph, c_no_of_nodes, c_no_of_edges, c_exponent_out, c_exponent_in, c_loops, c_multiple, c_finite_size_correction));
 
@@ -1389,10 +1825,38 @@ SEXP R_igraph_k_regular_game(SEXP no_of_nodes, SEXP k, SEXP directed, SEXP multi
 
   SEXP r_result;
                                         /* Convert input */
-  c_no_of_nodes=(igraph_integer_t) REAL(no_of_nodes)[0];
-  c_k=(igraph_integer_t) REAL(k)[0];
-  c_directed=LOGICAL(directed)[0];
-  c_multiple=LOGICAL(multiple)[0];
+  if (Rf_xlength(no_of_nodes) == 1) {
+    if (((igraph_integer_t) REAL(no_of_nodes)[0]) != REAL(no_of_nodes)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(no_of_nodes)[0]);
+    }
+    c_no_of_nodes = (igraph_integer_t) REAL(no_of_nodes)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(no_of_nodes));
+  }
+  if (Rf_xlength(k) == 1) {
+    if (((igraph_integer_t) REAL(k)[0]) != REAL(k)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(k)[0]);
+    }
+    c_k = (igraph_integer_t) REAL(k)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(k));
+  }
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
+  if (Rf_xlength(multiple) == 1) {
+    c_multiple = LOGICAL(multiple)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(multiple));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_k_regular_game(&c_graph, c_no_of_nodes, c_k, c_directed, c_multiple));
 
@@ -1422,12 +1886,31 @@ SEXP R_igraph_sbm_game(SEXP n, SEXP pref_matrix, SEXP block_sizes, SEXP directed
 
   SEXP r_result;
                                         /* Convert input */
-  c_n=(igraph_integer_t) REAL(n)[0];
+  if (Rf_xlength(n) == 1) {
+    if (((igraph_integer_t) REAL(n)[0]) != REAL(n)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(n)[0]);
+    }
+    c_n = (igraph_integer_t) REAL(n)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(n));
+  }
   R_SEXP_to_matrix(pref_matrix, &c_pref_matrix);
   R_SEXP_to_vector_int_copy(block_sizes, &c_block_sizes);
   IGRAPH_FINALLY(igraph_vector_int_destroy, &c_block_sizes);
-  c_directed=LOGICAL(directed)[0];
-  c_loops=LOGICAL(loops)[0];
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
+  if (Rf_xlength(loops) == 1) {
+    c_loops = LOGICAL(loops)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(loops));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_sbm_game(&c_graph, c_n, &c_pref_matrix, &c_block_sizes, c_directed, c_loops));
 
@@ -1459,11 +1942,34 @@ SEXP R_igraph_hsbm_game(SEXP n, SEXP m, SEXP rho, SEXP C, SEXP p) {
 
   SEXP r_result;
                                         /* Convert input */
-  c_n=(igraph_integer_t) REAL(n)[0];
-  c_m=(igraph_integer_t) REAL(m)[0];
+  if (Rf_xlength(n) == 1) {
+    if (((igraph_integer_t) REAL(n)[0]) != REAL(n)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(n)[0]);
+    }
+    c_n = (igraph_integer_t) REAL(n)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(n));
+  }
+  if (Rf_xlength(m) == 1) {
+    if (((igraph_integer_t) REAL(m)[0]) != REAL(m)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(m)[0]);
+    }
+    c_m = (igraph_integer_t) REAL(m)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(m));
+  }
   R_SEXP_to_vector(rho, &c_rho);
   R_SEXP_to_matrix(C, &c_C);
-  c_p=REAL(p)[0];
+  if (Rf_xlength(p) == 1) {
+    c_p = REAL(p)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(p));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_hsbm_game(&c_graph, c_n, c_m, &c_rho, &c_C, c_p));
 
@@ -1493,12 +1999,26 @@ SEXP R_igraph_hsbm_list_game(SEXP n, SEXP mlist, SEXP rholist, SEXP Clist, SEXP
 
   SEXP r_result;
                                         /* Convert input */
-  c_n=(igraph_integer_t) REAL(n)[0];
+  if (Rf_xlength(n) == 1) {
+    if (((igraph_integer_t) REAL(n)[0]) != REAL(n)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(n)[0]);
+    }
+    c_n = (igraph_integer_t) REAL(n)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(n));
+  }
   R_SEXP_to_vector_int_copy(mlist, &c_mlist);
   IGRAPH_FINALLY(igraph_vector_int_destroy, &c_mlist);
   R_igraph_SEXP_to_vector_list(rholist, &c_rholist);
   R_igraph_SEXP_to_matrixlist(Clist, &c_Clist);
-  c_p=REAL(p)[0];
+  if (Rf_xlength(p) == 1) {
+    c_p = REAL(p)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(p));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_hsbm_list_game(&c_graph, c_n, &c_mlist, &c_rholist, &c_Clist, c_p));
 
@@ -1530,8 +2050,18 @@ SEXP R_igraph_correlated_game(SEXP old_graph, SEXP corr, SEXP p, SEXP permutatio
   SEXP r_result;
                                         /* Convert input */
   R_SEXP_to_igraph(old_graph, &c_old_graph);
-  c_corr=REAL(corr)[0];
-  c_p=REAL(p)[0];
+  if (Rf_xlength(corr) == 1) {
+    c_corr = REAL(corr)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(corr));
+  }
+  if (Rf_xlength(p) == 1) {
+    c_p = REAL(p)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(p));
+  }
   if (!Rf_isNull(permutation)) {
     R_SEXP_to_vector_int_copy(permutation, &c_permutation);
     IGRAPH_FINALLY(igraph_vector_int_destroy, &c_permutation);
@@ -1572,10 +2102,34 @@ SEXP R_igraph_correlated_pair_game(SEXP n, SEXP corr, SEXP p, SEXP directed, SEX
 
   SEXP r_result, r_names;
                                         /* Convert input */
-  c_n=(igraph_integer_t) REAL(n)[0];
-  c_corr=REAL(corr)[0];
-  c_p=REAL(p)[0];
-  c_directed=LOGICAL(directed)[0];
+  if (Rf_xlength(n) == 1) {
+    if (((igraph_integer_t) REAL(n)[0]) != REAL(n)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(n)[0]);
+    }
+    c_n = (igraph_integer_t) REAL(n)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(n));
+  }
+  if (Rf_xlength(corr) == 1) {
+    c_corr = REAL(corr)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(corr));
+  }
+  if (Rf_xlength(p) == 1) {
+    c_p = REAL(p)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(p));
+  }
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
   if (!Rf_isNull(permutation)) {
     R_SEXP_to_vector_int_copy(permutation, &c_permutation);
     IGRAPH_FINALLY(igraph_vector_int_destroy, &c_permutation);
@@ -1623,7 +2177,12 @@ SEXP R_igraph_dot_product_game(SEXP vecs, SEXP directed) {
   SEXP r_result;
                                         /* Convert input */
   R_SEXP_to_matrix(vecs, &c_vecs);
-  c_directed=LOGICAL(directed)[0];
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_dot_product_game(&c_graph, &c_vecs, c_directed));
 
@@ -1652,10 +2211,38 @@ SEXP R_igraph_sample_sphere_surface(SEXP dim, SEXP n, SEXP radius, SEXP positive
 
   SEXP r_result;
                                         /* Convert input */
-  c_dim=(igraph_integer_t) REAL(dim)[0];
-  c_n=(igraph_integer_t) REAL(n)[0];
-  c_radius=REAL(radius)[0];
-  c_positive=LOGICAL(positive)[0];
+  if (Rf_xlength(dim) == 1) {
+    if (((igraph_integer_t) REAL(dim)[0]) != REAL(dim)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(dim)[0]);
+    }
+    c_dim = (igraph_integer_t) REAL(dim)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(dim));
+  }
+  if (Rf_xlength(n) == 1) {
+    if (((igraph_integer_t) REAL(n)[0]) != REAL(n)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(n)[0]);
+    }
+    c_n = (igraph_integer_t) REAL(n)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(n));
+  }
+  if (Rf_xlength(radius) == 1) {
+    c_radius = REAL(radius)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(radius));
+  }
+  if (Rf_xlength(positive) == 1) {
+    c_positive = LOGICAL(positive)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(positive));
+  }
   if (0 != igraph_matrix_init(&c_res, 0, 0)) {
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
@@ -1687,10 +2274,38 @@ SEXP R_igraph_sample_sphere_volume(SEXP dim, SEXP n, SEXP radius, SEXP positive)
 
   SEXP r_result;
                                         /* Convert input */
-  c_dim=(igraph_integer_t) REAL(dim)[0];
-  c_n=(igraph_integer_t) REAL(n)[0];
-  c_radius=REAL(radius)[0];
-  c_positive=LOGICAL(positive)[0];
+  if (Rf_xlength(dim) == 1) {
+    if (((igraph_integer_t) REAL(dim)[0]) != REAL(dim)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(dim)[0]);
+    }
+    c_dim = (igraph_integer_t) REAL(dim)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(dim));
+  }
+  if (Rf_xlength(n) == 1) {
+    if (((igraph_integer_t) REAL(n)[0]) != REAL(n)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(n)[0]);
+    }
+    c_n = (igraph_integer_t) REAL(n)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(n));
+  }
+  if (Rf_xlength(radius) == 1) {
+    c_radius = REAL(radius)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(radius));
+  }
+  if (Rf_xlength(positive) == 1) {
+    c_positive = LOGICAL(positive)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(positive));
+  }
   if (0 != igraph_matrix_init(&c_res, 0, 0)) {
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
@@ -1720,7 +2335,16 @@ SEXP R_igraph_sample_dirichlet(SEXP n, SEXP alpha) {
 
   SEXP r_result;
                                         /* Convert input */
-  c_n=(igraph_integer_t) REAL(n)[0];
+  if (Rf_xlength(n) == 1) {
+    if (((igraph_integer_t) REAL(n)[0]) != REAL(n)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(n)[0]);
+    }
+    c_n = (igraph_integer_t) REAL(n)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(n));
+  }
   R_SEXP_to_vector(alpha, &c_alpha);
   if (0 != igraph_matrix_init(&c_res, 0, 0)) {
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
@@ -1771,7 +2395,12 @@ SEXP R_igraph_closeness(SEXP graph, SEXP vids, SEXP mode, SEXP weights, SEXP nor
   R_SEXP_to_igraph_vs(vids, &c_graph, &c_vids, &c_vids_data);
   c_mode = (igraph_neimode_t) Rf_asInteger(mode);
   if (!Rf_isNull(weights)) { R_SEXP_to_vector(weights, &c_weights); }
-  c_normalized=LOGICAL(normalized)[0];
+  if (Rf_xlength(normalized) == 1) {
+    c_normalized = LOGICAL(normalized)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(normalized));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_closeness(&c_graph, &c_res, &c_reachable_count, &c_all_reachable, c_vids, c_mode, (Rf_isNull(weights) ? 0 : &c_weights), c_normalized));
 
@@ -1834,8 +2463,18 @@ SEXP R_igraph_closeness_cutoff(SEXP graph, SEXP vids, SEXP mode, SEXP weights, S
   R_SEXP_to_igraph_vs(vids, &c_graph, &c_vids, &c_vids_data);
   c_mode = (igraph_neimode_t) Rf_asInteger(mode);
   if (!Rf_isNull(weights)) { R_SEXP_to_vector(weights, &c_weights); }
-  c_normalized=LOGICAL(normalized)[0];
-  c_cutoff=REAL(cutoff)[0];
+  if (Rf_xlength(normalized) == 1) {
+    c_normalized = LOGICAL(normalized)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(normalized));
+  }
+  if (Rf_xlength(cutoff) == 1) {
+    c_cutoff = REAL(cutoff)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(cutoff));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_closeness_cutoff(&c_graph, &c_res, &c_reachable_count, &c_all_reachable, c_vids, c_mode, (Rf_isNull(weights) ? 0 : &c_weights), c_normalized, c_cutoff));
 
@@ -1931,7 +2570,12 @@ SEXP R_igraph_distances_cutoff(SEXP graph, SEXP from, SEXP to, SEXP mode, SEXP c
   igraph_vector_int_t c_to_data;
   R_SEXP_to_igraph_vs(to, &c_graph, &c_to, &c_to_data);
   c_mode = (igraph_neimode_t) Rf_asInteger(mode);
-  c_cutoff=REAL(cutoff)[0];
+  if (Rf_xlength(cutoff) == 1) {
+    c_cutoff = REAL(cutoff)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(cutoff));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_distances_cutoff(&c_graph, &c_res, c_from, c_to, c_mode, c_cutoff));
 
@@ -2241,7 +2885,12 @@ SEXP R_igraph_distances_dijkstra_cutoff(SEXP graph, SEXP from, SEXP to, SEXP wei
   R_SEXP_to_igraph_vs(to, &c_graph, &c_to, &c_to_data);
   if (!Rf_isNull(weights)) { R_SEXP_to_vector(weights, &c_weights); }
   c_mode = (igraph_neimode_t) Rf_asInteger(mode);
-  c_cutoff=REAL(cutoff)[0];
+  if (Rf_xlength(cutoff) == 1) {
+    c_cutoff = REAL(cutoff)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(cutoff));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_distances_dijkstra_cutoff(&c_graph, &c_res, c_from, c_to, (Rf_isNull(weights) ? 0 : &c_weights), c_mode, c_cutoff));
 
@@ -2531,7 +3180,16 @@ SEXP R_igraph_get_all_simple_paths(SEXP graph, SEXP from, SEXP to, SEXP cutoff,
   c_from = (igraph_integer_t) REAL(from)[0];
   igraph_vector_int_t c_to_data;
   R_SEXP_to_igraph_vs(to, &c_graph, &c_to, &c_to_data);
-  c_cutoff=(igraph_integer_t) REAL(cutoff)[0];
+  if (Rf_xlength(cutoff) == 1) {
+    if (((igraph_integer_t) REAL(cutoff)[0]) != REAL(cutoff)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(cutoff)[0]);
+    }
+    c_cutoff = (igraph_integer_t) REAL(cutoff)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(cutoff));
+  }
   c_mode = (igraph_neimode_t) Rf_asInteger(mode);
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_get_all_simple_paths(&c_graph, &c_res, c_from, c_to, c_cutoff, c_mode));
@@ -2576,7 +3234,16 @@ SEXP R_igraph_get_k_shortest_paths(SEXP graph, SEXP weights, SEXP k, SEXP from,
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
   IGRAPH_FINALLY(igraph_vector_int_list_destroy, &c_edge_paths);
-  c_k=(igraph_integer_t) REAL(k)[0];
+  if (Rf_xlength(k) == 1) {
+    if (((igraph_integer_t) REAL(k)[0]) != REAL(k)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(k)[0]);
+    }
+    c_k = (igraph_integer_t) REAL(k)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(k));
+  }
   c_from = (igraph_integer_t) REAL(from)[0];
   c_to = (igraph_integer_t) REAL(to)[0];
   c_mode = (igraph_neimode_t) Rf_asInteger(mode);
@@ -2838,7 +3505,12 @@ SEXP R_igraph_spanner(SEXP graph, SEXP stretch, SEXP weights) {
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
   IGRAPH_FINALLY(igraph_vector_int_destroy, &c_spanner);
-  c_stretch=REAL(stretch)[0];
+  if (Rf_xlength(stretch) == 1) {
+    c_stretch = REAL(stretch)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(stretch));
+  }
   if (!Rf_isNull(weights)) { R_SEXP_to_vector(weights, &c_weights); }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_spanner(&c_graph, &c_spanner, c_stretch, (Rf_isNull(weights) ? 0 : &c_weights)));
@@ -2875,9 +3547,19 @@ SEXP R_igraph_betweenness_cutoff(SEXP graph, SEXP vids, SEXP directed, SEXP weig
   IGRAPH_FINALLY(igraph_vector_destroy, &c_res);
   igraph_vector_int_t c_vids_data;
   R_SEXP_to_igraph_vs(vids, &c_graph, &c_vids, &c_vids_data);
-  c_directed=LOGICAL(directed)[0];
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
   if (!Rf_isNull(weights)) { R_SEXP_to_vector(weights, &c_weights); }
-  c_cutoff=REAL(cutoff)[0];
+  if (Rf_xlength(cutoff) == 1) {
+    c_cutoff = REAL(cutoff)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(cutoff));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_betweenness_cutoff(&c_graph, &c_res, c_vids, c_directed, (Rf_isNull(weights) ? 0 : &c_weights), c_cutoff));
 
@@ -2916,7 +3598,12 @@ SEXP R_igraph_betweenness_subset(SEXP graph, SEXP vids, SEXP directed, SEXP sour
   IGRAPH_FINALLY(igraph_vector_destroy, &c_res);
   igraph_vector_int_t c_vids_data;
   R_SEXP_to_igraph_vs(vids, &c_graph, &c_vids, &c_vids_data);
-  c_directed=LOGICAL(directed)[0];
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
   igraph_vector_int_t c_sources_data;
   R_SEXP_to_igraph_vs(sources, &c_graph, &c_sources, &c_sources_data);
   igraph_vector_int_t c_targets_data;
@@ -2959,7 +3646,12 @@ SEXP R_igraph_edge_betweenness(SEXP graph, SEXP directed, SEXP weights) {
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
   IGRAPH_FINALLY(igraph_vector_destroy, &c_res);
-  c_directed=LOGICAL(directed)[0];
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
   if (!Rf_isNull(weights)) { R_SEXP_to_vector(weights, &c_weights); }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_edge_betweenness(&c_graph, &c_res, c_directed, (Rf_isNull(weights) ? 0 : &c_weights)));
@@ -2993,9 +3685,19 @@ SEXP R_igraph_edge_betweenness_cutoff(SEXP graph, SEXP directed, SEXP weights, S
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
   IGRAPH_FINALLY(igraph_vector_destroy, &c_res);
-  c_directed=LOGICAL(directed)[0];
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
   if (!Rf_isNull(weights)) { R_SEXP_to_vector(weights, &c_weights); }
-  c_cutoff=REAL(cutoff)[0];
+  if (Rf_xlength(cutoff) == 1) {
+    c_cutoff = REAL(cutoff)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(cutoff));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_edge_betweenness_cutoff(&c_graph, &c_res, c_directed, (Rf_isNull(weights) ? 0 : &c_weights), c_cutoff));
 
@@ -3032,7 +3734,12 @@ SEXP R_igraph_edge_betweenness_subset(SEXP graph, SEXP eids, SEXP directed, SEXP
   IGRAPH_FINALLY(igraph_vector_destroy, &c_res);
   igraph_vector_int_t c_eids_data;
   R_SEXP_to_igraph_es(eids, &c_graph, &c_eids, &c_eids_data);
-  c_directed=LOGICAL(directed)[0];
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
   igraph_vector_int_t c_sources_data;
   R_SEXP_to_igraph_vs(sources, &c_graph, &c_sources, &c_sources_data);
   igraph_vector_int_t c_targets_data;
@@ -3082,8 +3789,18 @@ SEXP R_igraph_harmonic_centrality_cutoff(SEXP graph, SEXP vids, SEXP mode, SEXP
   R_SEXP_to_igraph_vs(vids, &c_graph, &c_vids, &c_vids_data);
   c_mode = (igraph_neimode_t) Rf_asInteger(mode);
   if (!Rf_isNull(weights)) { R_SEXP_to_vector(weights, &c_weights); }
-  c_normalized=LOGICAL(normalized)[0];
-  c_cutoff=REAL(cutoff)[0];
+  if (Rf_xlength(normalized) == 1) {
+    c_normalized = LOGICAL(normalized)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(normalized));
+  }
+  if (Rf_xlength(cutoff) == 1) {
+    c_cutoff = REAL(cutoff)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(cutoff));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_harmonic_centrality_cutoff(&c_graph, &c_res, c_vids, c_mode, (Rf_isNull(weights) ? 0 : &c_weights), c_normalized, c_cutoff));
 
@@ -3128,8 +3845,18 @@ SEXP R_igraph_personalized_pagerank(SEXP graph, SEXP algo, SEXP vids, SEXP direc
   IGRAPH_FINALLY(igraph_vector_destroy, &c_vector);
   igraph_vector_int_t c_vids_data;
   R_SEXP_to_igraph_vs(vids, &c_graph, &c_vids, &c_vids_data);
-  c_directed=LOGICAL(directed)[0];
-  c_damping=REAL(damping)[0];
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
+  if (Rf_xlength(damping) == 1) {
+    c_damping = REAL(damping)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(damping));
+  }
   if (!Rf_isNull(personalized)) {
     R_SEXP_to_vector(personalized, &c_personalized);
   }
@@ -3200,8 +3927,18 @@ SEXP R_igraph_personalized_pagerank_vs(SEXP graph, SEXP algo, SEXP vids, SEXP di
   IGRAPH_FINALLY(igraph_vector_destroy, &c_vector);
   igraph_vector_int_t c_vids_data;
   R_SEXP_to_igraph_vs(vids, &c_graph, &c_vids, &c_vids_data);
-  c_directed=LOGICAL(directed)[0];
-  c_damping=REAL(damping)[0];
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
+  if (Rf_xlength(damping) == 1) {
+    c_damping = REAL(damping)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(damping));
+  }
   igraph_vector_int_t c_reset_vids_data;
   R_SEXP_to_igraph_vs(reset_vids, &c_graph, &c_reset_vids, &c_reset_vids_data);
   if (!Rf_isNull(weights)) { R_SEXP_to_vector(weights, &c_weights); }
@@ -3293,7 +4030,12 @@ SEXP R_igraph_subgraph_from_edges(SEXP graph, SEXP eids, SEXP delete_vertices) {
   R_SEXP_to_igraph(graph, &c_graph);
   igraph_vector_int_t c_eids_data;
   R_SEXP_to_igraph_es(eids, &c_graph, &c_eids, &c_eids_data);
-  c_delete_vertices=LOGICAL(delete_vertices)[0];
+  if (Rf_xlength(delete_vertices) == 1) {
+    c_delete_vertices = LOGICAL(delete_vertices)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(delete_vertices));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_subgraph_from_edges(&c_graph, &c_res, c_eids, c_delete_vertices));
 
@@ -3357,8 +4099,18 @@ SEXP R_igraph_average_path_length_dijkstra(SEXP graph, SEXP weights, SEXP direct
                                         /* Convert input */
   R_SEXP_to_igraph(graph, &c_graph);
   if (!Rf_isNull(weights)) { R_SEXP_to_vector(weights, &c_weights); }
-  c_directed=LOGICAL(directed)[0];
-  c_unconn=LOGICAL(unconn)[0];
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
+  if (Rf_xlength(unconn) == 1) {
+    c_unconn = LOGICAL(unconn)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(unconn));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_average_path_length_dijkstra(&c_graph, &c_res, &c_unconn_pairs, (Rf_isNull(weights) ? 0 : &c_weights), c_directed, c_unconn));
 
@@ -3399,7 +4151,12 @@ SEXP R_igraph_path_length_hist(SEXP graph, SEXP directed) {
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
   IGRAPH_FINALLY(igraph_vector_destroy, &c_res);
-  c_directed=LOGICAL(directed)[0];
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_path_length_hist(&c_graph, &c_res, &c_unconnected, c_directed));
 
@@ -3436,8 +4193,18 @@ SEXP R_igraph_simplify(SEXP graph, SEXP remove_multiple, SEXP remove_loops, SEXP
                                         /* Convert input */
   R_SEXP_to_igraph_copy(graph, &c_graph);
   IGRAPH_FINALLY(igraph_destroy, &c_graph);
-  c_remove_multiple=LOGICAL(remove_multiple)[0];
-  c_remove_loops=LOGICAL(remove_loops)[0];
+  if (Rf_xlength(remove_multiple) == 1) {
+    c_remove_multiple = LOGICAL(remove_multiple)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(remove_multiple));
+  }
+  if (Rf_xlength(remove_loops) == 1) {
+    c_remove_loops = LOGICAL(remove_loops)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(remove_loops));
+  }
   R_SEXP_to_attr_comb(edge_attr_comb, &c_edge_attr_comb);
   IGRAPH_FINALLY(igraph_attribute_combination_destroy, &c_edge_attr_comb);
                                         /* Call igraph */
@@ -3477,9 +4244,28 @@ SEXP R_igraph_ecc(SEXP graph, SEXP eids, SEXP k, SEXP offset, SEXP normalize) {
   IGRAPH_FINALLY(igraph_vector_destroy, &c_res);
   igraph_vector_int_t c_eids_data;
   R_SEXP_to_igraph_es(eids, &c_graph, &c_eids, &c_eids_data);
-  c_k=(igraph_integer_t) REAL(k)[0];
-  c_offset=LOGICAL(offset)[0];
-  c_normalize=LOGICAL(normalize)[0];
+  if (Rf_xlength(k) == 1) {
+    if (((igraph_integer_t) REAL(k)[0]) != REAL(k)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(k)[0]);
+    }
+    c_k = (igraph_integer_t) REAL(k)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(k));
+  }
+  if (Rf_xlength(offset) == 1) {
+    c_offset = LOGICAL(offset)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(offset));
+  }
+  if (Rf_xlength(normalize) == 1) {
+    c_normalize = LOGICAL(normalize)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(normalize));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_ecc(&c_graph, &c_res, c_eids, c_k, c_offset, c_normalize));
 
@@ -3796,8 +4582,18 @@ SEXP R_igraph_eigenvector_centrality(SEXP graph, SEXP directed, SEXP scale, SEXP
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
   IGRAPH_FINALLY(igraph_vector_destroy, &c_vector);
-  c_directed=LOGICAL(directed)[0];
-  c_scale=LOGICAL(scale)[0];
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
+  if (Rf_xlength(scale) == 1) {
+    c_scale = LOGICAL(scale)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(scale));
+  }
   if (!Rf_isNull(weights)) { R_SEXP_to_vector(weights, &c_weights); }
   R_SEXP_to_igraph_arpack_options(options, &c_options);
                                         /* Call igraph */
@@ -3846,7 +4642,12 @@ SEXP R_igraph_hub_score(SEXP graph, SEXP scale, SEXP weights, SEXP options) {
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
   IGRAPH_FINALLY(igraph_vector_destroy, &c_vector);
-  c_scale=LOGICAL(scale)[0];
+  if (Rf_xlength(scale) == 1) {
+    c_scale = LOGICAL(scale)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(scale));
+  }
   if (!Rf_isNull(weights)) { R_SEXP_to_vector(weights, &c_weights); }
   R_SEXP_to_igraph_arpack_options(options, &c_options);
                                         /* Call igraph */
@@ -3895,7 +4696,12 @@ SEXP R_igraph_authority_score(SEXP graph, SEXP scale, SEXP weights, SEXP options
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
   IGRAPH_FINALLY(igraph_vector_destroy, &c_vector);
-  c_scale=LOGICAL(scale)[0];
+  if (Rf_xlength(scale) == 1) {
+    c_scale = LOGICAL(scale)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(scale));
+  }
   if (!Rf_isNull(weights)) { R_SEXP_to_vector(weights, &c_weights); }
   R_SEXP_to_igraph_arpack_options(options, &c_options);
                                         /* Call igraph */
@@ -3950,7 +4756,12 @@ SEXP R_igraph_hub_and_authority_scores(SEXP graph, SEXP scale, SEXP weights, SEX
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
   IGRAPH_FINALLY(igraph_vector_destroy, &c_authority_vector);
-  c_scale=LOGICAL(scale)[0];
+  if (Rf_xlength(scale) == 1) {
+    c_scale = LOGICAL(scale)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(scale));
+  }
   if (!Rf_isNull(weights)) { R_SEXP_to_vector(weights, &c_weights); }
   R_SEXP_to_igraph_arpack_options(options, &c_options);
                                         /* Call igraph */
@@ -4052,7 +4863,12 @@ SEXP R_igraph_is_mutual(SEXP graph, SEXP es, SEXP loops) {
   IGRAPH_FINALLY(igraph_vector_bool_destroy, &c_res);
   igraph_vector_int_t c_es_data;
   R_SEXP_to_igraph_es(es, &c_graph, &c_es, &c_es_data);
-  c_loops=LOGICAL(loops)[0];
+  if (Rf_xlength(loops) == 1) {
+    c_loops = LOGICAL(loops)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(loops));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_is_mutual(&c_graph, &c_res, c_es, c_loops));
 
@@ -4081,7 +4897,12 @@ SEXP R_igraph_has_mutual(SEXP graph, SEXP loops) {
   SEXP r_result;
                                         /* Convert input */
   R_SEXP_to_igraph(graph, &c_graph);
-  c_loops=LOGICAL(loops)[0];
+  if (Rf_xlength(loops) == 1) {
+    c_loops = LOGICAL(loops)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(loops));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_has_mutual(&c_graph, &c_res, c_loops));
 
@@ -4218,7 +5039,12 @@ SEXP R_igraph_degree_correlation_vector(SEXP graph, SEXP weights, SEXP from_mode
   IGRAPH_FINALLY(igraph_vector_destroy, &c_knnk);
   c_from_mode = (igraph_neimode_t) Rf_asInteger(from_mode);
   c_to_mode = (igraph_neimode_t) Rf_asInteger(to_mode);
-  c_directed_neighbors=LOGICAL(directed_neighbors)[0];
+  if (Rf_xlength(directed_neighbors) == 1) {
+    c_directed_neighbors = LOGICAL(directed_neighbors)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed_neighbors));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_degree_correlation_vector(&c_graph, (Rf_isNull(weights) ? 0 : &c_weights), &c_knnk, c_from_mode, c_to_mode, c_directed_neighbors));
 
@@ -4255,7 +5081,12 @@ SEXP R_igraph_strength(SEXP graph, SEXP vids, SEXP mode, SEXP loops, SEXP weight
   igraph_vector_int_t c_vids_data;
   R_SEXP_to_igraph_vs(vids, &c_graph, &c_vids, &c_vids_data);
   c_mode = (igraph_neimode_t) Rf_asInteger(mode);
-  c_loops=LOGICAL(loops)[0];
+  if (Rf_xlength(loops) == 1) {
+    c_loops = LOGICAL(loops)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(loops));
+  }
   if (!Rf_isNull(weights)) { R_SEXP_to_vector(weights, &c_weights); }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_strength(&c_graph, &c_res, c_vids, c_mode, c_loops, (Rf_isNull(weights) ? 0 : &c_weights)));
@@ -4284,8 +5115,18 @@ SEXP R_igraph_centralization(SEXP scores, SEXP theoretical_max, SEXP normalized)
   SEXP r_result;
                                         /* Convert input */
   R_SEXP_to_vector(scores, &c_scores);
-  c_theoretical_max=REAL(theoretical_max)[0];
-  c_normalized=LOGICAL(normalized)[0];
+  if (Rf_xlength(theoretical_max) == 1) {
+    c_theoretical_max = REAL(theoretical_max)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(theoretical_max));
+  }
+  if (Rf_xlength(normalized) == 1) {
+    c_normalized = LOGICAL(normalized)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(normalized));
+  }
                                         /* Call igraph */
   c_result=igraph_centralization(&c_scores, c_theoretical_max, c_normalized);
 
@@ -4322,8 +5163,18 @@ SEXP R_igraph_centralization_degree(SEXP graph, SEXP mode, SEXP loops, SEXP norm
   }
   IGRAPH_FINALLY(igraph_vector_destroy, &c_res);
   c_mode = (igraph_neimode_t) Rf_asInteger(mode);
-  c_loops=LOGICAL(loops)[0];
-  c_normalized=LOGICAL(normalized)[0];
+  if (Rf_xlength(loops) == 1) {
+    c_loops = LOGICAL(loops)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(loops));
+  }
+  if (Rf_xlength(normalized) == 1) {
+    c_normalized = LOGICAL(normalized)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(normalized));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_centralization_degree(&c_graph, &c_res, c_mode, c_loops, &c_centralization, &c_theoretical_max, c_normalized));
 
@@ -4367,9 +5218,23 @@ SEXP R_igraph_centralization_degree_tmax(SEXP graph, SEXP nodes, SEXP mode, SEXP
   if (!Rf_isNull(graph)) {
     R_SEXP_to_igraph(graph, &c_graph);
   }
-  c_nodes=(igraph_integer_t) REAL(nodes)[0];
+  if (Rf_xlength(nodes) == 1) {
+    if (((igraph_integer_t) REAL(nodes)[0]) != REAL(nodes)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(nodes)[0]);
+    }
+    c_nodes = (igraph_integer_t) REAL(nodes)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(nodes));
+  }
   c_mode = (igraph_neimode_t) Rf_asInteger(mode);
-  c_loops=LOGICAL(loops)[0];
+  if (Rf_xlength(loops) == 1) {
+    c_loops = LOGICAL(loops)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(loops));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_centralization_degree_tmax((Rf_isNull(graph) ? 0 : &c_graph), c_nodes, c_mode, c_loops, &c_res));
 
@@ -4404,8 +5269,18 @@ SEXP R_igraph_centralization_betweenness(SEXP graph, SEXP directed, SEXP normali
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
   IGRAPH_FINALLY(igraph_vector_destroy, &c_res);
-  c_directed=LOGICAL(directed)[0];
-  c_normalized=LOGICAL(normalized)[0];
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
+  if (Rf_xlength(normalized) == 1) {
+    c_normalized = LOGICAL(normalized)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(normalized));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_centralization_betweenness(&c_graph, &c_res, c_directed, &c_centralization, &c_theoretical_max, c_normalized));
 
@@ -4448,8 +5323,22 @@ SEXP R_igraph_centralization_betweenness_tmax(SEXP graph, SEXP nodes, SEXP direc
   if (!Rf_isNull(graph)) {
     R_SEXP_to_igraph(graph, &c_graph);
   }
-  c_nodes=(igraph_integer_t) REAL(nodes)[0];
-  c_directed=LOGICAL(directed)[0];
+  if (Rf_xlength(nodes) == 1) {
+    if (((igraph_integer_t) REAL(nodes)[0]) != REAL(nodes)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(nodes)[0]);
+    }
+    c_nodes = (igraph_integer_t) REAL(nodes)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(nodes));
+  }
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_centralization_betweenness_tmax((Rf_isNull(graph) ? 0 : &c_graph), c_nodes, c_directed, &c_res));
 
@@ -4485,7 +5374,12 @@ SEXP R_igraph_centralization_closeness(SEXP graph, SEXP mode, SEXP normalized) {
   }
   IGRAPH_FINALLY(igraph_vector_destroy, &c_res);
   c_mode = (igraph_neimode_t) Rf_asInteger(mode);
-  c_normalized=LOGICAL(normalized)[0];
+  if (Rf_xlength(normalized) == 1) {
+    c_normalized = LOGICAL(normalized)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(normalized));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_centralization_closeness(&c_graph, &c_res, c_mode, &c_centralization, &c_theoretical_max, c_normalized));
 
@@ -4528,7 +5422,16 @@ SEXP R_igraph_centralization_closeness_tmax(SEXP graph, SEXP nodes, SEXP mode) {
   if (!Rf_isNull(graph)) {
     R_SEXP_to_igraph(graph, &c_graph);
   }
-  c_nodes=(igraph_integer_t) REAL(nodes)[0];
+  if (Rf_xlength(nodes) == 1) {
+    if (((igraph_integer_t) REAL(nodes)[0]) != REAL(nodes)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(nodes)[0]);
+    }
+    c_nodes = (igraph_integer_t) REAL(nodes)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(nodes));
+  }
   c_mode = (igraph_neimode_t) Rf_asInteger(mode);
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_centralization_closeness_tmax((Rf_isNull(graph) ? 0 : &c_graph), c_nodes, c_mode, &c_res));
@@ -4567,11 +5470,26 @@ SEXP R_igraph_centralization_eigenvector_centrality(SEXP graph, SEXP directed, S
   if (0 != igraph_vector_init(&c_vector, 0)) {
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
-  IGRAPH_FINALLY(igraph_vector_destroy, &c_vector);
-  c_directed=LOGICAL(directed)[0];
-  c_scale=LOGICAL(scale)[0];
+  IGRAPH_FINALLY(igraph_vector_destroy, &c_vector);
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
+  if (Rf_xlength(scale) == 1) {
+    c_scale = LOGICAL(scale)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(scale));
+  }
   R_SEXP_to_igraph_arpack_options(options, &c_options);
-  c_normalized=LOGICAL(normalized)[0];
+  if (Rf_xlength(normalized) == 1) {
+    c_normalized = LOGICAL(normalized)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(normalized));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_centralization_eigenvector_centrality(&c_graph, &c_vector, &c_value, c_directed, c_scale, &c_options, &c_centralization, &c_theoretical_max, c_normalized));
 
@@ -4622,9 +5540,28 @@ SEXP R_igraph_centralization_eigenvector_centrality_tmax(SEXP graph, SEXP nodes,
   if (!Rf_isNull(graph)) {
     R_SEXP_to_igraph(graph, &c_graph);
   }
-  c_nodes=(igraph_integer_t) REAL(nodes)[0];
-  c_directed=LOGICAL(directed)[0];
-  c_scale=LOGICAL(scale)[0];
+  if (Rf_xlength(nodes) == 1) {
+    if (((igraph_integer_t) REAL(nodes)[0]) != REAL(nodes)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(nodes)[0]);
+    }
+    c_nodes = (igraph_integer_t) REAL(nodes)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(nodes));
+  }
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
+  if (Rf_xlength(scale) == 1) {
+    c_scale = LOGICAL(scale)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(scale));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_centralization_eigenvector_centrality_tmax((Rf_isNull(graph) ? 0 : &c_graph), c_nodes, c_directed, c_scale, &c_res));
 
@@ -4654,8 +5591,18 @@ SEXP R_igraph_assortativity_nominal(SEXP graph, SEXP types, SEXP directed, SEXP
   R_SEXP_to_igraph(graph, &c_graph);
   R_SEXP_to_vector_int_copy(types, &c_types);
   IGRAPH_FINALLY(igraph_vector_int_destroy, &c_types);
-  c_directed=LOGICAL(directed)[0];
-  c_normalized=LOGICAL(normalized)[0];
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
+  if (Rf_xlength(normalized) == 1) {
+    c_normalized = LOGICAL(normalized)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(normalized));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_assortativity_nominal(&c_graph, &c_types, &c_res, c_directed, c_normalized));
 
@@ -4690,8 +5637,18 @@ SEXP R_igraph_assortativity(SEXP graph, SEXP values, SEXP values_in, SEXP direct
   if (!Rf_isNull(values_in)) {
     R_SEXP_to_vector(values_in, &c_values_in);
   }
-  c_directed=LOGICAL(directed)[0];
-  c_normalized=LOGICAL(normalized)[0];
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
+  if (Rf_xlength(normalized) == 1) {
+    c_normalized = LOGICAL(normalized)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(normalized));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_assortativity(&c_graph, &c_values, (Rf_isNull(values_in) ? 0 : &c_values_in), &c_res, c_directed, c_normalized));
 
@@ -4717,7 +5674,12 @@ SEXP R_igraph_assortativity_degree(SEXP graph, SEXP directed) {
   SEXP r_result;
                                         /* Convert input */
   R_SEXP_to_igraph(graph, &c_graph);
-  c_directed=LOGICAL(directed)[0];
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_assortativity_degree(&c_graph, &c_res, c_directed));
 
@@ -4750,8 +5712,26 @@ SEXP R_igraph_joint_degree_matrix(SEXP graph, SEXP weights, SEXP max_out_degree,
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
   IGRAPH_FINALLY(igraph_matrix_destroy, &c_jdm);
-  c_max_out_degree=(igraph_integer_t) REAL(max_out_degree)[0];
-  c_max_in_degree=(igraph_integer_t) REAL(max_in_degree)[0];
+  if (Rf_xlength(max_out_degree) == 1) {
+    if (((igraph_integer_t) REAL(max_out_degree)[0]) != REAL(max_out_degree)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(max_out_degree)[0]);
+    }
+    c_max_out_degree = (igraph_integer_t) REAL(max_out_degree)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(max_out_degree));
+  }
+  if (Rf_xlength(max_in_degree) == 1) {
+    if (((igraph_integer_t) REAL(max_in_degree)[0]) != REAL(max_in_degree)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(max_in_degree)[0]);
+    }
+    c_max_in_degree = (igraph_integer_t) REAL(max_in_degree)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(max_in_degree));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_joint_degree_matrix(&c_graph, (Rf_isNull(weights) ? 0 : &c_weights), &c_jdm, c_max_out_degree, c_max_in_degree));
 
@@ -4791,10 +5771,38 @@ SEXP R_igraph_joint_degree_distribution(SEXP graph, SEXP weights, SEXP from_mode
   IGRAPH_FINALLY(igraph_matrix_destroy, &c_p);
   c_from_mode = (igraph_neimode_t) Rf_asInteger(from_mode);
   c_to_mode = (igraph_neimode_t) Rf_asInteger(to_mode);
-  c_directed_neighbors=LOGICAL(directed_neighbors)[0];
-  c_normalized=LOGICAL(normalized)[0];
-  c_max_from_degree=(igraph_integer_t) REAL(max_from_degree)[0];
-  c_max_to_degree=(igraph_integer_t) REAL(max_to_degree)[0];
+  if (Rf_xlength(directed_neighbors) == 1) {
+    c_directed_neighbors = LOGICAL(directed_neighbors)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed_neighbors));
+  }
+  if (Rf_xlength(normalized) == 1) {
+    c_normalized = LOGICAL(normalized)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(normalized));
+  }
+  if (Rf_xlength(max_from_degree) == 1) {
+    if (((igraph_integer_t) REAL(max_from_degree)[0]) != REAL(max_from_degree)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(max_from_degree)[0]);
+    }
+    c_max_from_degree = (igraph_integer_t) REAL(max_from_degree)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(max_from_degree));
+  }
+  if (Rf_xlength(max_to_degree) == 1) {
+    if (((igraph_integer_t) REAL(max_to_degree)[0]) != REAL(max_to_degree)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(max_to_degree)[0]);
+    }
+    c_max_to_degree = (igraph_integer_t) REAL(max_to_degree)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(max_to_degree));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_joint_degree_distribution(&c_graph, (Rf_isNull(weights) ? 0 : &c_weights), &c_p, c_from_mode, c_to_mode, c_directed_neighbors, c_normalized, c_max_from_degree, c_max_to_degree));
 
@@ -4834,8 +5842,18 @@ SEXP R_igraph_joint_type_distribution(SEXP graph, SEXP weights, SEXP from_types,
   IGRAPH_FINALLY(igraph_vector_int_destroy, &c_from_types);
   R_SEXP_to_vector_int_copy(to_types, &c_to_types);
   IGRAPH_FINALLY(igraph_vector_int_destroy, &c_to_types);
-  c_directed=LOGICAL(directed)[0];
-  c_normalized=LOGICAL(normalized)[0];
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
+  if (Rf_xlength(normalized) == 1) {
+    c_normalized = LOGICAL(normalized)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(normalized));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_joint_type_distribution(&c_graph, (Rf_isNull(weights) ? 0 : &c_weights), &c_p, &c_from_types, &c_to_types, c_directed, c_normalized));
 
@@ -5101,8 +6119,18 @@ SEXP R_igraph_pseudo_diameter(SEXP graph, SEXP start_vid, SEXP directed, SEXP un
   c_start_vid = (igraph_integer_t) REAL(start_vid)[0];
   c_from=0;
   c_to=0;
-  c_directed=LOGICAL(directed)[0];
-  c_unconnected=LOGICAL(unconnected)[0];
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
+  if (Rf_xlength(unconnected) == 1) {
+    c_unconnected = LOGICAL(unconnected)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(unconnected));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_pseudo_diameter(&c_graph, &c_diameter, c_start_vid, &c_from, &c_to, c_directed, c_unconnected));
 
@@ -5152,8 +6180,18 @@ SEXP R_igraph_pseudo_diameter_dijkstra(SEXP graph, SEXP weights, SEXP start_vid,
   c_start_vid = (igraph_integer_t) REAL(start_vid)[0];
   c_from=0;
   c_to=0;
-  c_directed=LOGICAL(directed)[0];
-  c_unconnected=LOGICAL(unconnected)[0];
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
+  if (Rf_xlength(unconnected) == 1) {
+    c_unconnected = LOGICAL(unconnected)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(unconnected));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_pseudo_diameter_dijkstra(&c_graph, (Rf_isNull(weights) ? 0 : &c_weights), &c_diameter, c_start_vid, &c_from, &c_to, c_directed, c_unconnected));
 
@@ -5245,7 +6283,16 @@ SEXP R_igraph_random_walk(SEXP graph, SEXP weights, SEXP start, SEXP mode, SEXP
   IGRAPH_FINALLY(igraph_vector_int_destroy, &c_edges);
   c_start = (igraph_integer_t) REAL(start)[0];
   c_mode = (igraph_neimode_t) Rf_asInteger(mode);
-  c_steps=(igraph_integer_t) REAL(steps)[0];
+  if (Rf_xlength(steps) == 1) {
+    if (((igraph_integer_t) REAL(steps)[0]) != REAL(steps)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(steps)[0]);
+    }
+    c_steps = (igraph_integer_t) REAL(steps)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(steps));
+  }
   c_stuck = (igraph_random_walk_stuck_t) Rf_asInteger(stuck);
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_random_walk(&c_graph, (Rf_isNull(weights) ? 0 : &c_weights), &c_vertices, &c_edges, c_start, c_mode, c_steps, c_stuck));
@@ -5294,7 +6341,16 @@ SEXP R_igraph_random_edge_walk(SEXP graph, SEXP weights, SEXP start, SEXP mode,
   IGRAPH_FINALLY(igraph_vector_int_destroy, &c_edgewalk);
   c_start = (igraph_integer_t) REAL(start)[0];
   c_mode = (igraph_neimode_t) Rf_asInteger(mode);
-  c_steps=(igraph_integer_t) REAL(steps)[0];
+  if (Rf_xlength(steps) == 1) {
+    if (((igraph_integer_t) REAL(steps)[0]) != REAL(steps)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(steps)[0]);
+    }
+    c_steps = (igraph_integer_t) REAL(steps)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(steps));
+  }
   c_stuck = (igraph_random_walk_stuck_t) Rf_asInteger(stuck);
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_random_edge_walk(&c_graph, (Rf_isNull(weights) ? 0 : &c_weights), &c_edgewalk, c_start, c_mode, c_steps, c_stuck));
@@ -5324,7 +6380,12 @@ SEXP R_igraph_global_efficiency(SEXP graph, SEXP weights, SEXP directed) {
                                         /* Convert input */
   R_SEXP_to_igraph(graph, &c_graph);
   if (!Rf_isNull(weights)) { R_SEXP_to_vector(weights, &c_weights); }
-  c_directed=LOGICAL(directed)[0];
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_global_efficiency(&c_graph, &c_res, (Rf_isNull(weights) ? 0 : &c_weights), c_directed));
 
@@ -5360,7 +6421,12 @@ SEXP R_igraph_local_efficiency(SEXP graph, SEXP vids, SEXP weights, SEXP directe
   igraph_vector_int_t c_vids_data;
   R_SEXP_to_igraph_vs(vids, &c_graph, &c_vids, &c_vids_data);
   if (!Rf_isNull(weights)) { R_SEXP_to_vector(weights, &c_weights); }
-  c_directed=LOGICAL(directed)[0];
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
   c_mode = (igraph_neimode_t) Rf_asInteger(mode);
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_local_efficiency(&c_graph, &c_res, c_vids, (Rf_isNull(weights) ? 0 : &c_weights), c_directed, c_mode));
@@ -5393,7 +6459,12 @@ SEXP R_igraph_average_local_efficiency(SEXP graph, SEXP weights, SEXP directed,
                                         /* Convert input */
   R_SEXP_to_igraph(graph, &c_graph);
   if (!Rf_isNull(weights)) { R_SEXP_to_vector(weights, &c_weights); }
-  c_directed=LOGICAL(directed)[0];
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
   c_mode = (igraph_neimode_t) Rf_asInteger(mode);
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_average_local_efficiency(&c_graph, &c_res, (Rf_isNull(weights) ? 0 : &c_weights), c_directed, c_mode));
@@ -5630,7 +6701,12 @@ SEXP R_igraph_create_bipartite(SEXP types, SEXP edges, SEXP directed) {
   if (!Rf_isNull(types)) { R_SEXP_to_vector_bool(types, &c_types); }
   R_SEXP_to_vector_int_copy(edges, &c_edges);
   IGRAPH_FINALLY(igraph_vector_int_destroy, &c_edges);
-  c_directed=LOGICAL(directed)[0];
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_create_bipartite(&c_graph, (Rf_isNull(types) ? 0 : &c_types), &c_edges, c_directed));
 
@@ -5668,9 +6744,19 @@ SEXP R_igraph_biadjacency(SEXP incidence, SEXP directed, SEXP mode, SEXP multipl
   }
   IGRAPH_FINALLY(igraph_vector_bool_destroy, &c_types);
   R_SEXP_to_matrix(incidence, &c_incidence);
-  c_directed=LOGICAL(directed)[0];
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
   c_mode = (igraph_neimode_t) Rf_asInteger(mode);
-  c_multiple=LOGICAL(multiple)[0];
+  if (Rf_xlength(multiple) == 1) {
+    c_multiple = LOGICAL(multiple)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(multiple));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_biadjacency(&c_graph, &c_types, &c_incidence, c_directed, c_mode, c_multiple));
 
@@ -5814,10 +6900,38 @@ SEXP R_igraph_bipartite_game_gnp(SEXP n1, SEXP n2, SEXP p, SEXP directed, SEXP m
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
   IGRAPH_FINALLY(igraph_vector_bool_destroy, &c_types);
-  c_n1=(igraph_integer_t) REAL(n1)[0];
-  c_n2=(igraph_integer_t) REAL(n2)[0];
-  c_p=REAL(p)[0];
-  c_directed=LOGICAL(directed)[0];
+  if (Rf_xlength(n1) == 1) {
+    if (((igraph_integer_t) REAL(n1)[0]) != REAL(n1)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(n1)[0]);
+    }
+    c_n1 = (igraph_integer_t) REAL(n1)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(n1));
+  }
+  if (Rf_xlength(n2) == 1) {
+    if (((igraph_integer_t) REAL(n2)[0]) != REAL(n2)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(n2)[0]);
+    }
+    c_n2 = (igraph_integer_t) REAL(n2)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(n2));
+  }
+  if (Rf_xlength(p) == 1) {
+    c_p = REAL(p)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(p));
+  }
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
   c_mode = (igraph_neimode_t) Rf_asInteger(mode);
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_bipartite_game_gnp(&c_graph, &c_types, c_n1, c_n2, c_p, c_directed, c_mode));
@@ -5864,10 +6978,42 @@ SEXP R_igraph_bipartite_game_gnm(SEXP n1, SEXP n2, SEXP m, SEXP directed, SEXP m
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
   IGRAPH_FINALLY(igraph_vector_bool_destroy, &c_types);
-  c_n1=(igraph_integer_t) REAL(n1)[0];
-  c_n2=(igraph_integer_t) REAL(n2)[0];
-  c_m=(igraph_integer_t) REAL(m)[0];
-  c_directed=LOGICAL(directed)[0];
+  if (Rf_xlength(n1) == 1) {
+    if (((igraph_integer_t) REAL(n1)[0]) != REAL(n1)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(n1)[0]);
+    }
+    c_n1 = (igraph_integer_t) REAL(n1)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(n1));
+  }
+  if (Rf_xlength(n2) == 1) {
+    if (((igraph_integer_t) REAL(n2)[0]) != REAL(n2)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(n2)[0]);
+    }
+    c_n2 = (igraph_integer_t) REAL(n2)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(n2));
+  }
+  if (Rf_xlength(m) == 1) {
+    if (((igraph_integer_t) REAL(m)[0]) != REAL(m)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(m)[0]);
+    }
+    c_m = (igraph_integer_t) REAL(m)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(m));
+  }
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
   c_mode = (igraph_neimode_t) Rf_asInteger(mode);
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_bipartite_game_gnm(&c_graph, &c_types, c_n1, c_n2, c_m, c_directed, c_mode));
@@ -5917,11 +7063,48 @@ SEXP R_igraph_bipartite_game(SEXP type, SEXP n1, SEXP n2, SEXP p, SEXP m, SEXP d
   }
   IGRAPH_FINALLY(igraph_vector_bool_destroy, &c_types);
   c_type = (igraph_erdos_renyi_t) Rf_asInteger(type);
-  c_n1=(igraph_integer_t) REAL(n1)[0];
-  c_n2=(igraph_integer_t) REAL(n2)[0];
-  c_p=REAL(p)[0];
-  c_m=(igraph_integer_t) REAL(m)[0];
-  c_directed=LOGICAL(directed)[0];
+  if (Rf_xlength(n1) == 1) {
+    if (((igraph_integer_t) REAL(n1)[0]) != REAL(n1)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(n1)[0]);
+    }
+    c_n1 = (igraph_integer_t) REAL(n1)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(n1));
+  }
+  if (Rf_xlength(n2) == 1) {
+    if (((igraph_integer_t) REAL(n2)[0]) != REAL(n2)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(n2)[0]);
+    }
+    c_n2 = (igraph_integer_t) REAL(n2)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(n2));
+  }
+  if (Rf_xlength(p) == 1) {
+    c_p = REAL(p)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(p));
+  }
+  if (Rf_xlength(m) == 1) {
+    if (((igraph_integer_t) REAL(m)[0]) != REAL(m)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(m)[0]);
+    }
+    c_m = (igraph_integer_t) REAL(m)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(m));
+  }
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
   c_mode = (igraph_neimode_t) Rf_asInteger(mode);
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_bipartite_game(&c_graph, &c_types, c_type, c_n1, c_n2, c_p, c_m, c_directed, c_mode));
@@ -6247,8 +7430,26 @@ SEXP R_igraph_cliques(SEXP graph, SEXP min_size, SEXP max_size) {
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
   IGRAPH_FINALLY(igraph_vector_int_list_destroy, &c_res);
-  c_min_size=(igraph_integer_t) REAL(min_size)[0];
-  c_max_size=(igraph_integer_t) REAL(max_size)[0];
+  if (Rf_xlength(min_size) == 1) {
+    if (((igraph_integer_t) REAL(min_size)[0]) != REAL(min_size)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(min_size)[0]);
+    }
+    c_min_size = (igraph_integer_t) REAL(min_size)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(min_size));
+  }
+  if (Rf_xlength(max_size) == 1) {
+    if (((igraph_integer_t) REAL(max_size)[0]) != REAL(max_size)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(max_size)[0]);
+    }
+    c_max_size = (igraph_integer_t) REAL(max_size)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(max_size));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_cliques(&c_graph, &c_res, c_min_size, c_max_size));
 
@@ -6280,8 +7481,26 @@ SEXP R_igraph_clique_size_hist(SEXP graph, SEXP min_size, SEXP max_size) {
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
   IGRAPH_FINALLY(igraph_vector_destroy, &c_hist);
-  c_min_size=(igraph_integer_t) REAL(min_size)[0];
-  c_max_size=(igraph_integer_t) REAL(max_size)[0];
+  if (Rf_xlength(min_size) == 1) {
+    if (((igraph_integer_t) REAL(min_size)[0]) != REAL(min_size)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(min_size)[0]);
+    }
+    c_min_size = (igraph_integer_t) REAL(min_size)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(min_size));
+  }
+  if (Rf_xlength(max_size) == 1) {
+    if (((igraph_integer_t) REAL(max_size)[0]) != REAL(max_size)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(max_size)[0]);
+    }
+    c_max_size = (igraph_integer_t) REAL(max_size)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(max_size));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_clique_size_hist(&c_graph, &c_hist, c_min_size, c_max_size));
 
@@ -6348,8 +7567,26 @@ SEXP R_igraph_maximal_cliques_subset(SEXP graph, SEXP subset, SEXP outfile, SEXP
   }
   IGRAPH_FINALLY(igraph_vector_int_list_destroy, &c_res);
   c_no=0;
-  c_min_size=(igraph_integer_t) REAL(min_size)[0];
-  c_max_size=(igraph_integer_t) REAL(max_size)[0];
+  if (Rf_xlength(min_size) == 1) {
+    if (((igraph_integer_t) REAL(min_size)[0]) != REAL(min_size)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(min_size)[0]);
+    }
+    c_min_size = (igraph_integer_t) REAL(min_size)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(min_size));
+  }
+  if (Rf_xlength(max_size) == 1) {
+    if (((igraph_integer_t) REAL(max_size)[0]) != REAL(max_size)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(max_size)[0]);
+    }
+    c_max_size = (igraph_integer_t) REAL(max_size)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(max_size));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_maximal_cliques_subset(&c_graph, &c_subset, &c_res, &c_no, c_outfile, c_min_size, c_max_size));
 
@@ -6390,8 +7627,26 @@ SEXP R_igraph_maximal_cliques_hist(SEXP graph, SEXP min_size, SEXP max_size) {
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
   IGRAPH_FINALLY(igraph_vector_destroy, &c_hist);
-  c_min_size=(igraph_integer_t) REAL(min_size)[0];
-  c_max_size=(igraph_integer_t) REAL(max_size)[0];
+  if (Rf_xlength(min_size) == 1) {
+    if (((igraph_integer_t) REAL(min_size)[0]) != REAL(min_size)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(min_size)[0]);
+    }
+    c_min_size = (igraph_integer_t) REAL(min_size)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(min_size));
+  }
+  if (Rf_xlength(max_size) == 1) {
+    if (((igraph_integer_t) REAL(max_size)[0]) != REAL(max_size)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(max_size)[0]);
+    }
+    c_max_size = (igraph_integer_t) REAL(max_size)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(max_size));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_maximal_cliques_hist(&c_graph, &c_hist, c_min_size, c_max_size));
 
@@ -6451,9 +7706,24 @@ SEXP R_igraph_weighted_cliques(SEXP graph, SEXP vertex_weights, SEXP min_weight,
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
   IGRAPH_FINALLY(igraph_vector_int_list_destroy, &c_res);
-  c_min_weight=REAL(min_weight)[0];
-  c_max_weight=REAL(max_weight)[0];
-  c_maximal=LOGICAL(maximal)[0];
+  if (Rf_xlength(min_weight) == 1) {
+    c_min_weight = REAL(min_weight)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(min_weight));
+  }
+  if (Rf_xlength(max_weight) == 1) {
+    c_max_weight = REAL(max_weight)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(max_weight));
+  }
+  if (Rf_xlength(maximal) == 1) {
+    c_maximal = LOGICAL(maximal)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(maximal));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_weighted_cliques(&c_graph, (Rf_isNull(vertex_weights) ? 0 : &c_vertex_weights), &c_res, c_min_weight, c_max_weight, c_maximal));
 
@@ -6582,7 +7852,16 @@ SEXP R_igraph_layout_grid(SEXP graph, SEXP width) {
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
   IGRAPH_FINALLY(igraph_matrix_destroy, &c_res);
-  c_width=(igraph_integer_t) REAL(width)[0];
+  if (Rf_xlength(width) == 1) {
+    if (((igraph_integer_t) REAL(width)[0]) != REAL(width)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(width)[0]);
+    }
+    c_width = (igraph_integer_t) REAL(width)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(width));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_layout_grid(&c_graph, &c_res, c_width));
 
@@ -6614,8 +7893,26 @@ SEXP R_igraph_layout_grid_3d(SEXP graph, SEXP width, SEXP height) {
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
   IGRAPH_FINALLY(igraph_matrix_destroy, &c_res);
-  c_width=(igraph_integer_t) REAL(width)[0];
-  c_height=(igraph_integer_t) REAL(height)[0];
+  if (Rf_xlength(width) == 1) {
+    if (((igraph_integer_t) REAL(width)[0]) != REAL(width)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(width)[0]);
+    }
+    c_width = (igraph_integer_t) REAL(width)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(width));
+  }
+  if (Rf_xlength(height) == 1) {
+    if (((igraph_integer_t) REAL(height)[0]) != REAL(height)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(height)[0]);
+    }
+    c_height = (igraph_integer_t) REAL(height)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(height));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_layout_grid_3d(&c_graph, &c_res, c_width, c_height));
 
@@ -6680,7 +7977,12 @@ SEXP R_igraph_layout_drl(SEXP graph, SEXP res, SEXP use_seed, SEXP options, SEXP
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
   IGRAPH_FINALLY(igraph_matrix_destroy, &c_res);
-  c_use_seed=LOGICAL(use_seed)[0];
+  if (Rf_xlength(use_seed) == 1) {
+    c_use_seed = LOGICAL(use_seed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(use_seed));
+  }
   R_SEXP_to_igraph_layout_drl_options(options, &c_options);
   if (!Rf_isNull(weights)) { R_SEXP_to_vector(weights, &c_weights); }
                                         /* Call igraph */
@@ -6714,7 +8016,12 @@ SEXP R_igraph_layout_drl_3d(SEXP graph, SEXP res, SEXP use_seed, SEXP options, S
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
   IGRAPH_FINALLY(igraph_matrix_destroy, &c_res);
-  c_use_seed=LOGICAL(use_seed)[0];
+  if (Rf_xlength(use_seed) == 1) {
+    c_use_seed = LOGICAL(use_seed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(use_seed));
+  }
   R_SEXP_to_igraph_layout_drl_options(options, &c_options);
   if (!Rf_isNull(weights)) { R_SEXP_to_vector(weights, &c_weights); }
                                         /* Call igraph */
@@ -6766,9 +8073,28 @@ SEXP R_igraph_layout_sugiyama(SEXP graph, SEXP layers, SEXP hgap, SEXP vgap, SEX
     IGRAPH_R_CHECK(igraph_vector_int_init(&c_layers, 0));
     IGRAPH_FINALLY(igraph_vector_int_destroy, &c_layers);
   }
-  c_hgap=REAL(hgap)[0];
-  c_vgap=REAL(vgap)[0];
-  c_maxiter=(igraph_integer_t) REAL(maxiter)[0];
+  if (Rf_xlength(hgap) == 1) {
+    c_hgap = REAL(hgap)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(hgap));
+  }
+  if (Rf_xlength(vgap) == 1) {
+    c_vgap = REAL(vgap)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(vgap));
+  }
+  if (Rf_xlength(maxiter) == 1) {
+    if (((igraph_integer_t) REAL(maxiter)[0]) != REAL(maxiter)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(maxiter)[0]);
+    }
+    c_maxiter = (igraph_integer_t) REAL(maxiter)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(maxiter));
+  }
   if (!Rf_isNull(weights)) { R_SEXP_to_vector(weights, &c_weights); }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_layout_sugiyama(&c_graph, &c_res, &c_extd_graph, &c_extd_to_orig_eids, (Rf_isNull(layers) ? 0 : &c_layers), c_hgap, c_vgap, c_maxiter, (Rf_isNull(weights) ? 0 : &c_weights)));
@@ -6822,7 +8148,16 @@ SEXP R_igraph_layout_mds(SEXP graph, SEXP dist, SEXP dim) {
   if (!Rf_isNull(dist)) {
     R_SEXP_to_matrix(dist, &c_dist);
   }
-  c_dim=(igraph_integer_t) REAL(dim)[0];
+  if (Rf_xlength(dim) == 1) {
+    if (((igraph_integer_t) REAL(dim)[0]) != REAL(dim)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(dim)[0]);
+    }
+    c_dim = (igraph_integer_t) REAL(dim)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(dim));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_layout_mds(&c_graph, &c_res, (Rf_isNull(dist) ? 0 : &c_dist), c_dim));
 
@@ -6857,9 +8192,28 @@ SEXP R_igraph_layout_bipartite(SEXP graph, SEXP types, SEXP hgap, SEXP vgap, SEX
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
   IGRAPH_FINALLY(igraph_matrix_destroy, &c_res);
-  c_hgap=REAL(hgap)[0];
-  c_vgap=REAL(vgap)[0];
-  c_maxiter=(igraph_integer_t) REAL(maxiter)[0];
+  if (Rf_xlength(hgap) == 1) {
+    c_hgap = REAL(hgap)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(hgap));
+  }
+  if (Rf_xlength(vgap) == 1) {
+    c_vgap = REAL(vgap)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(vgap));
+  }
+  if (Rf_xlength(maxiter) == 1) {
+    if (((igraph_integer_t) REAL(maxiter)[0]) != REAL(maxiter)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(maxiter)[0]);
+    }
+    c_maxiter = (igraph_integer_t) REAL(maxiter)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(maxiter));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_layout_bipartite(&c_graph, (Rf_isNull(types) ? 0 : &c_types), &c_res, c_hgap, c_vgap, c_maxiter));
 
@@ -6893,11 +8247,40 @@ SEXP R_igraph_layout_gem(SEXP graph, SEXP res, SEXP use_seed, SEXP maxiter, SEXP
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
   IGRAPH_FINALLY(igraph_matrix_destroy, &c_res);
-  c_use_seed=LOGICAL(use_seed)[0];
-  c_maxiter=(igraph_integer_t) REAL(maxiter)[0];
-  c_temp_max=REAL(temp_max)[0];
-  c_temp_min=REAL(temp_min)[0];
-  c_temp_init=REAL(temp_init)[0];
+  if (Rf_xlength(use_seed) == 1) {
+    c_use_seed = LOGICAL(use_seed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(use_seed));
+  }
+  if (Rf_xlength(maxiter) == 1) {
+    if (((igraph_integer_t) REAL(maxiter)[0]) != REAL(maxiter)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(maxiter)[0]);
+    }
+    c_maxiter = (igraph_integer_t) REAL(maxiter)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(maxiter));
+  }
+  if (Rf_xlength(temp_max) == 1) {
+    c_temp_max = REAL(temp_max)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(temp_max));
+  }
+  if (Rf_xlength(temp_min) == 1) {
+    c_temp_min = REAL(temp_min)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(temp_min));
+  }
+  if (Rf_xlength(temp_init) == 1) {
+    c_temp_init = REAL(temp_init)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(temp_init));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_layout_gem(&c_graph, &c_res, c_use_seed, c_maxiter, c_temp_max, c_temp_min, c_temp_init));
 
@@ -6935,15 +8318,68 @@ SEXP R_igraph_layout_davidson_harel(SEXP graph, SEXP res, SEXP use_seed, SEXP ma
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
   IGRAPH_FINALLY(igraph_matrix_destroy, &c_res);
-  c_use_seed=LOGICAL(use_seed)[0];
-  c_maxiter=(igraph_integer_t) REAL(maxiter)[0];
-  c_fineiter=(igraph_integer_t) REAL(fineiter)[0];
-  c_cool_fact=REAL(cool_fact)[0];
-  c_weight_node_dist=REAL(weight_node_dist)[0];
-  c_weight_border=REAL(weight_border)[0];
-  c_weight_edge_lengths=REAL(weight_edge_lengths)[0];
-  c_weight_edge_crossings=REAL(weight_edge_crossings)[0];
-  c_weight_node_edge_dist=REAL(weight_node_edge_dist)[0];
+  if (Rf_xlength(use_seed) == 1) {
+    c_use_seed = LOGICAL(use_seed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(use_seed));
+  }
+  if (Rf_xlength(maxiter) == 1) {
+    if (((igraph_integer_t) REAL(maxiter)[0]) != REAL(maxiter)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(maxiter)[0]);
+    }
+    c_maxiter = (igraph_integer_t) REAL(maxiter)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(maxiter));
+  }
+  if (Rf_xlength(fineiter) == 1) {
+    if (((igraph_integer_t) REAL(fineiter)[0]) != REAL(fineiter)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(fineiter)[0]);
+    }
+    c_fineiter = (igraph_integer_t) REAL(fineiter)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(fineiter));
+  }
+  if (Rf_xlength(cool_fact) == 1) {
+    c_cool_fact = REAL(cool_fact)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(cool_fact));
+  }
+  if (Rf_xlength(weight_node_dist) == 1) {
+    c_weight_node_dist = REAL(weight_node_dist)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(weight_node_dist));
+  }
+  if (Rf_xlength(weight_border) == 1) {
+    c_weight_border = REAL(weight_border)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(weight_border));
+  }
+  if (Rf_xlength(weight_edge_lengths) == 1) {
+    c_weight_edge_lengths = REAL(weight_edge_lengths)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(weight_edge_lengths));
+  }
+  if (Rf_xlength(weight_edge_crossings) == 1) {
+    c_weight_edge_crossings = REAL(weight_edge_crossings)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(weight_edge_crossings));
+  }
+  if (Rf_xlength(weight_node_edge_dist) == 1) {
+    c_weight_node_edge_dist = REAL(weight_node_edge_dist)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(weight_node_edge_dist));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_layout_davidson_harel(&c_graph, &c_res, c_use_seed, c_maxiter, c_fineiter, c_cool_fact, c_weight_node_dist, c_weight_border, c_weight_edge_lengths, c_weight_edge_crossings, c_weight_node_edge_dist));
 
@@ -6977,13 +8413,37 @@ SEXP R_igraph_layout_umap(SEXP graph, SEXP res, SEXP use_seed, SEXP distances, S
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
   IGRAPH_FINALLY(igraph_matrix_destroy, &c_res);
-  c_use_seed=LOGICAL(use_seed)[0];
+  if (Rf_xlength(use_seed) == 1) {
+    c_use_seed = LOGICAL(use_seed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(use_seed));
+  }
   if (!Rf_isNull(distances)) {
     R_SEXP_to_vector(distances, &c_distances);
   }
-  c_min_dist=REAL(min_dist)[0];
-  c_epochs=(igraph_integer_t) REAL(epochs)[0];
-  c_distances_are_weights=LOGICAL(distances_are_weights)[0];
+  if (Rf_xlength(min_dist) == 1) {
+    c_min_dist = REAL(min_dist)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(min_dist));
+  }
+  if (Rf_xlength(epochs) == 1) {
+    if (((igraph_integer_t) REAL(epochs)[0]) != REAL(epochs)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(epochs)[0]);
+    }
+    c_epochs = (igraph_integer_t) REAL(epochs)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(epochs));
+  }
+  if (Rf_xlength(distances_are_weights) == 1) {
+    c_distances_are_weights = LOGICAL(distances_are_weights)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(distances_are_weights));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_layout_umap(&c_graph, &c_res, c_use_seed, (Rf_isNull(distances) ? 0 : &c_distances), c_min_dist, c_epochs, c_distances_are_weights));
 
@@ -7017,13 +8477,37 @@ SEXP R_igraph_layout_umap_3d(SEXP graph, SEXP res, SEXP use_seed, SEXP distances
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
   IGRAPH_FINALLY(igraph_matrix_destroy, &c_res);
-  c_use_seed=LOGICAL(use_seed)[0];
+  if (Rf_xlength(use_seed) == 1) {
+    c_use_seed = LOGICAL(use_seed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(use_seed));
+  }
   if (!Rf_isNull(distances)) {
     R_SEXP_to_vector(distances, &c_distances);
   }
-  c_min_dist=REAL(min_dist)[0];
-  c_epochs=(igraph_integer_t) REAL(epochs)[0];
-  c_distances_are_weights=LOGICAL(distances_are_weights)[0];
+  if (Rf_xlength(min_dist) == 1) {
+    c_min_dist = REAL(min_dist)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(min_dist));
+  }
+  if (Rf_xlength(epochs) == 1) {
+    if (((igraph_integer_t) REAL(epochs)[0]) != REAL(epochs)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(epochs)[0]);
+    }
+    c_epochs = (igraph_integer_t) REAL(epochs)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(epochs));
+  }
+  if (Rf_xlength(distances_are_weights) == 1) {
+    c_distances_are_weights = LOGICAL(distances_are_weights)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(distances_are_weights));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_layout_umap_3d(&c_graph, &c_res, c_use_seed, (Rf_isNull(distances) ? 0 : &c_distances), c_min_dist, c_epochs, c_distances_are_weights));
 
@@ -7089,7 +8573,12 @@ SEXP R_igraph_similarity_dice(SEXP graph, SEXP vids, SEXP mode, SEXP loops) {
   igraph_vector_int_t c_vids_data;
   R_SEXP_to_igraph_vs(vids, &c_graph, &c_vids, &c_vids_data);
   c_mode = (igraph_neimode_t) Rf_asInteger(mode);
-  c_loops=LOGICAL(loops)[0];
+  if (Rf_xlength(loops) == 1) {
+    c_loops = LOGICAL(loops)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(loops));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_similarity_dice(&c_graph, &c_res, c_vids, c_mode, c_loops));
 
@@ -7127,7 +8616,12 @@ SEXP R_igraph_similarity_dice_es(SEXP graph, SEXP es, SEXP mode, SEXP loops) {
   igraph_vector_int_t c_es_data;
   R_SEXP_to_igraph_es(es, &c_graph, &c_es, &c_es_data);
   c_mode = (igraph_neimode_t) Rf_asInteger(mode);
-  c_loops=LOGICAL(loops)[0];
+  if (Rf_xlength(loops) == 1) {
+    c_loops = LOGICAL(loops)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(loops));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_similarity_dice_es(&c_graph, &c_res, c_es, c_mode, c_loops));
 
@@ -7164,7 +8658,12 @@ SEXP R_igraph_similarity_dice_pairs(SEXP graph, SEXP pairs, SEXP mode, SEXP loop
   IGRAPH_FINALLY(igraph_vector_destroy, &c_res);
   R_SEXP_to_vector_int_copy(pairs, &c_pairs);
   c_mode = (igraph_neimode_t) Rf_asInteger(mode);
-  c_loops=LOGICAL(loops)[0];
+  if (Rf_xlength(loops) == 1) {
+    c_loops = LOGICAL(loops)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(loops));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_similarity_dice_pairs(&c_graph, &c_res, &c_pairs, c_mode, c_loops));
 
@@ -7236,7 +8735,12 @@ SEXP R_igraph_similarity_jaccard(SEXP graph, SEXP vids, SEXP mode, SEXP loops) {
   igraph_vector_int_t c_vids_data;
   R_SEXP_to_igraph_vs(vids, &c_graph, &c_vids, &c_vids_data);
   c_mode = (igraph_neimode_t) Rf_asInteger(mode);
-  c_loops=LOGICAL(loops)[0];
+  if (Rf_xlength(loops) == 1) {
+    c_loops = LOGICAL(loops)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(loops));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_similarity_jaccard(&c_graph, &c_res, c_vids, c_mode, c_loops));
 
@@ -7274,7 +8778,12 @@ SEXP R_igraph_similarity_jaccard_es(SEXP graph, SEXP es, SEXP mode, SEXP loops)
   igraph_vector_int_t c_es_data;
   R_SEXP_to_igraph_es(es, &c_graph, &c_es, &c_es_data);
   c_mode = (igraph_neimode_t) Rf_asInteger(mode);
-  c_loops=LOGICAL(loops)[0];
+  if (Rf_xlength(loops) == 1) {
+    c_loops = LOGICAL(loops)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(loops));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_similarity_jaccard_es(&c_graph, &c_res, c_es, c_mode, c_loops));
 
@@ -7311,7 +8820,12 @@ SEXP R_igraph_similarity_jaccard_pairs(SEXP graph, SEXP pairs, SEXP mode, SEXP l
   IGRAPH_FINALLY(igraph_vector_destroy, &c_res);
   R_SEXP_to_vector_int_copy(pairs, &c_pairs);
   c_mode = (igraph_neimode_t) Rf_asInteger(mode);
-  c_loops=LOGICAL(loops)[0];
+  if (Rf_xlength(loops) == 1) {
+    c_loops = LOGICAL(loops)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(loops));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_similarity_jaccard_pairs(&c_graph, &c_res, &c_pairs, c_mode, c_loops));
 
@@ -7378,8 +8892,18 @@ SEXP R_igraph_modularity(SEXP graph, SEXP membership, SEXP weights, SEXP resolut
   R_SEXP_to_vector_int_copy(membership, &c_membership);
   IGRAPH_FINALLY(igraph_vector_int_destroy, &c_membership);
   if (!Rf_isNull(weights)) { R_SEXP_to_vector(weights, &c_weights); }
-  c_resolution=REAL(resolution)[0];
-  c_directed=LOGICAL(directed)[0];
+  if (Rf_xlength(resolution) == 1) {
+    c_resolution = REAL(resolution)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(resolution));
+  }
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_modularity(&c_graph, &c_membership, (Rf_isNull(weights) ? 0 : (Rf_isNull(weights) ? 0 : &c_weights)), c_resolution, c_directed, &c_modularity));
 
@@ -7410,12 +8934,22 @@ SEXP R_igraph_modularity_matrix(SEXP graph, SEXP weights, SEXP resolution, SEXP
                                         /* Convert input */
   R_SEXP_to_igraph(graph, &c_graph);
   if (!Rf_isNull(weights)) { R_SEXP_to_vector(weights, &c_weights); }
-  c_resolution=REAL(resolution)[0];
+  if (Rf_xlength(resolution) == 1) {
+    c_resolution = REAL(resolution)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(resolution));
+  }
   if (0 != igraph_matrix_init(&c_modmat, 0, 0)) {
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
   IGRAPH_FINALLY(igraph_matrix_destroy, &c_modmat);
-  c_directed=LOGICAL(directed)[0];
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_modularity_matrix(&c_graph, (Rf_isNull(weights) ? 0 : (Rf_isNull(weights) ? 0 : &c_weights)), c_resolution, &c_modmat, c_directed));
 
@@ -7442,7 +8976,16 @@ SEXP R_igraph_community_fluid_communities(SEXP graph, SEXP no_of_communities) {
   SEXP r_result;
                                         /* Convert input */
   R_SEXP_to_igraph(graph, &c_graph);
-  c_no_of_communities=(igraph_integer_t) REAL(no_of_communities)[0];
+  if (Rf_xlength(no_of_communities) == 1) {
+    if (((igraph_integer_t) REAL(no_of_communities)[0]) != REAL(no_of_communities)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(no_of_communities)[0]);
+    }
+    c_no_of_communities = (igraph_integer_t) REAL(no_of_communities)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(no_of_communities));
+  }
   if (0 != igraph_vector_int_init(&c_membership, 0)) {
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
@@ -7526,7 +9069,12 @@ SEXP R_igraph_community_multilevel(SEXP graph, SEXP weights, SEXP resolution) {
                                         /* Convert input */
   R_SEXP_to_igraph(graph, &c_graph);
   if (!Rf_isNull(weights)) { R_SEXP_to_vector(weights, &c_weights); }
-  c_resolution=REAL(resolution)[0];
+  if (Rf_xlength(resolution) == 1) {
+    c_resolution = REAL(resolution)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(resolution));
+  }
   if (0 != igraph_vector_int_init(&c_membership, 0)) {
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
@@ -7632,10 +9180,34 @@ SEXP R_igraph_community_leiden(SEXP graph, SEXP weights, SEXP vertex_weights, SE
   R_SEXP_to_igraph(graph, &c_graph);
   if (!Rf_isNull(weights)) { R_SEXP_to_vector(weights, &c_weights); }
   if (!Rf_isNull(vertex_weights)) { R_SEXP_to_vector(vertex_weights, &c_vertex_weights); }
-  c_resolution=REAL(resolution)[0];
-  c_beta=REAL(beta)[0];
-  c_start=LOGICAL(start)[0];
-  c_n_iterations=(igraph_integer_t) REAL(n_iterations)[0];
+  if (Rf_xlength(resolution) == 1) {
+    c_resolution = REAL(resolution)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(resolution));
+  }
+  if (Rf_xlength(beta) == 1) {
+    c_beta = REAL(beta)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(beta));
+  }
+  if (Rf_xlength(start) == 1) {
+    c_start = LOGICAL(start)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(start));
+  }
+  if (Rf_xlength(n_iterations) == 1) {
+    if (((igraph_integer_t) REAL(n_iterations)[0]) != REAL(n_iterations)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(n_iterations)[0]);
+    }
+    c_n_iterations = (igraph_integer_t) REAL(n_iterations)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(n_iterations));
+  }
   if (!Rf_isNull(membership)) {
     R_SEXP_to_vector_int_copy(membership, &c_membership);
     IGRAPH_FINALLY(igraph_vector_int_destroy, &c_membership);
@@ -7734,7 +9306,16 @@ SEXP R_igraph_community_infomap(SEXP graph, SEXP e_weights, SEXP v_weights, SEXP
   R_SEXP_to_igraph(graph, &c_graph);
   if (!Rf_isNull(e_weights)) { R_SEXP_to_vector(e_weights, &c_e_weights); }
   if (!Rf_isNull(v_weights)) { R_SEXP_to_vector(v_weights, &c_v_weights); }
-  c_nb_trials=(igraph_integer_t) REAL(nb_trials)[0];
+  if (Rf_xlength(nb_trials) == 1) {
+    if (((igraph_integer_t) REAL(nb_trials)[0]) != REAL(nb_trials)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(nb_trials)[0]);
+    }
+    c_nb_trials = (igraph_integer_t) REAL(nb_trials)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(nb_trials));
+  }
   if (0 != igraph_vector_int_init(&c_membership, 0)) {
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
@@ -7778,8 +9359,22 @@ SEXP R_igraph_hrg_fit(SEXP graph, SEXP hrg, SEXP start, SEXP steps) {
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
   IGRAPH_FINALLY(igraph_hrg_destroy, &c_hrg);
-  c_start=LOGICAL(start)[0];
-  c_steps=(igraph_integer_t) REAL(steps)[0];
+  if (Rf_xlength(start) == 1) {
+    c_start = LOGICAL(start)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(start));
+  }
+  if (Rf_xlength(steps) == 1) {
+    if (((igraph_integer_t) REAL(steps)[0]) != REAL(steps)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(steps)[0]);
+    }
+    c_steps = (igraph_integer_t) REAL(steps)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(steps));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_hrg_fit(&c_graph, &c_hrg, c_start, c_steps));
 
@@ -7836,7 +9431,16 @@ SEXP R_igraph_hrg_sample_many(SEXP hrg, SEXP num_samples) {
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
   IGRAPH_FINALLY(igraph_graph_list_destroy, &c_samples);
-  c_num_samples=(igraph_integer_t) REAL(num_samples)[0];
+  if (Rf_xlength(num_samples) == 1) {
+    if (((igraph_integer_t) REAL(num_samples)[0]) != REAL(num_samples)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(num_samples)[0]);
+    }
+    c_num_samples = (igraph_integer_t) REAL(num_samples)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(num_samples));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_hrg_sample_many(&c_hrg, &c_samples, c_num_samples));
 
@@ -7905,8 +9509,22 @@ SEXP R_igraph_hrg_consensus(SEXP graph, SEXP hrg, SEXP start, SEXP num_samples)
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
   IGRAPH_FINALLY(igraph_hrg_destroy, &c_hrg);
-  c_start=LOGICAL(start)[0];
-  c_num_samples=(igraph_integer_t) REAL(num_samples)[0];
+  if (Rf_xlength(start) == 1) {
+    c_start = LOGICAL(start)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(start));
+  }
+  if (Rf_xlength(num_samples) == 1) {
+    if (((igraph_integer_t) REAL(num_samples)[0]) != REAL(num_samples)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(num_samples)[0]);
+    }
+    c_num_samples = (igraph_integer_t) REAL(num_samples)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(num_samples));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_hrg_consensus(&c_graph, &c_parents, &c_weights, &c_hrg, c_start, c_num_samples));
 
@@ -7965,9 +9583,32 @@ SEXP R_igraph_hrg_predict(SEXP graph, SEXP hrg, SEXP start, SEXP num_samples, SE
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
   IGRAPH_FINALLY(igraph_hrg_destroy, &c_hrg);
-  c_start=LOGICAL(start)[0];
-  c_num_samples=(igraph_integer_t) REAL(num_samples)[0];
-  c_num_bins=(igraph_integer_t) REAL(num_bins)[0];
+  if (Rf_xlength(start) == 1) {
+    c_start = LOGICAL(start)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(start));
+  }
+  if (Rf_xlength(num_samples) == 1) {
+    if (((igraph_integer_t) REAL(num_samples)[0]) != REAL(num_samples)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(num_samples)[0]);
+    }
+    c_num_samples = (igraph_integer_t) REAL(num_samples)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(num_samples));
+  }
+  if (Rf_xlength(num_bins) == 1) {
+    if (((igraph_integer_t) REAL(num_bins)[0]) != REAL(num_bins)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(num_bins)[0]);
+    }
+    c_num_bins = (igraph_integer_t) REAL(num_bins)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(num_bins));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_hrg_predict(&c_graph, &c_edges, &c_prob, &c_hrg, c_start, c_num_samples, c_num_bins));
 
@@ -8041,7 +9682,16 @@ SEXP R_igraph_hrg_resize(SEXP hrg, SEXP newsize) {
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
   IGRAPH_FINALLY(igraph_hrg_destroy, &c_hrg);
-  c_newsize=(igraph_integer_t) REAL(newsize)[0];
+  if (Rf_xlength(newsize) == 1) {
+    if (((igraph_integer_t) REAL(newsize)[0]) != REAL(newsize)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(newsize)[0]);
+    }
+    c_newsize = (igraph_integer_t) REAL(newsize)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(newsize));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_hrg_resize(&c_hrg, c_newsize));
 
@@ -8172,7 +9822,12 @@ SEXP R_igraph_get_stochastic(SEXP graph, SEXP column_wise, SEXP weights) {
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
   IGRAPH_FINALLY(igraph_matrix_destroy, &c_res);
-  c_column_wise=LOGICAL(column_wise)[0];
+  if (Rf_xlength(column_wise) == 1) {
+    c_column_wise = LOGICAL(column_wise)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(column_wise));
+  }
   if (!Rf_isNull(weights)) { R_SEXP_to_vector(weights, &c_weights); }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_get_stochastic(&c_graph, &c_res, c_column_wise, (Rf_isNull(weights) ? 0 : &c_weights)));
@@ -8205,7 +9860,12 @@ SEXP R_igraph_get_stochastic_sparse(SEXP graph, SEXP column_wise, SEXP weights)
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
   IGRAPH_FINALLY(igraph_sparsemat_destroy, &c_sparsemat);
-  c_column_wise=LOGICAL(column_wise)[0];
+  if (Rf_xlength(column_wise) == 1) {
+    c_column_wise = LOGICAL(column_wise)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(column_wise));
+  }
   if (!Rf_isNull(weights)) { R_SEXP_to_vector(weights, &c_weights); }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_get_stochastic_sparse(&c_graph, &c_sparsemat, c_column_wise, (Rf_isNull(weights) ? 0 : &c_weights)));
@@ -8313,7 +9973,12 @@ SEXP R_igraph_read_graph_dimacs_flow(SEXP instream, SEXP directed) {
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
   IGRAPH_FINALLY(igraph_vector_destroy, &c_capacity);
-  c_directed=LOGICAL(directed)[0];
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_read_graph_dimacs_flow(&c_graph, c_instream, &c_problem, &c_label, &c_source, &c_target, &c_capacity, c_directed));
 
@@ -8642,7 +10307,16 @@ SEXP R_igraph_local_scan_k_ecount(SEXP graph, SEXP k, SEXP weights, SEXP mode) {
   SEXP r_result;
                                         /* Convert input */
   R_SEXP_to_igraph(graph, &c_graph);
-  c_k=(igraph_integer_t) REAL(k)[0];
+  if (Rf_xlength(k) == 1) {
+    if (((igraph_integer_t) REAL(k)[0]) != REAL(k)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(k)[0]);
+    }
+    c_k = (igraph_integer_t) REAL(k)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(k));
+  }
   if (0 != igraph_vector_init(&c_res, 0)) {
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
@@ -8679,7 +10353,16 @@ SEXP R_igraph_local_scan_k_ecount_them(SEXP us, SEXP them, SEXP k, SEXP weights_
                                         /* Convert input */
   R_SEXP_to_igraph(us, &c_us);
   R_SEXP_to_igraph(them, &c_them);
-  c_k=(igraph_integer_t) REAL(k)[0];
+  if (Rf_xlength(k) == 1) {
+    if (((igraph_integer_t) REAL(k)[0]) != REAL(k)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(k)[0]);
+    }
+    c_k = (igraph_integer_t) REAL(k)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(k));
+  }
   if (0 != igraph_vector_init(&c_res, 0)) {
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
@@ -9549,9 +11232,32 @@ SEXP R_igraph_isoclass_create(SEXP size, SEXP number, SEXP directed) {
 
   SEXP r_result;
                                         /* Convert input */
-  c_size=(igraph_integer_t) REAL(size)[0];
-  c_number=(igraph_integer_t) REAL(number)[0];
-  c_directed=LOGICAL(directed)[0];
+  if (Rf_xlength(size) == 1) {
+    if (((igraph_integer_t) REAL(size)[0]) != REAL(size)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(size)[0]);
+    }
+    c_size = (igraph_integer_t) REAL(size)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(size));
+  }
+  if (Rf_xlength(number) == 1) {
+    if (((igraph_integer_t) REAL(number)[0]) != REAL(number)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(number)[0]);
+    }
+    c_number = (igraph_integer_t) REAL(number)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(number));
+  }
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_isoclass_create(&c_graph, c_size, c_number, c_directed));
 
@@ -10453,8 +12159,22 @@ SEXP R_igraph_graph_count(SEXP n, SEXP directed) {
 
   SEXP r_result;
                                         /* Convert input */
-  c_n=(igraph_integer_t) REAL(n)[0];
-  c_directed=LOGICAL(directed)[0];
+  if (Rf_xlength(n) == 1) {
+    if (((igraph_integer_t) REAL(n)[0]) != REAL(n)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(n)[0]);
+    }
+    c_n = (igraph_integer_t) REAL(n)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(n));
+  }
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
   c_count=0;
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_graph_count(c_n, c_directed, &c_count));
@@ -10556,7 +12276,12 @@ SEXP R_igraph_maximum_bipartite_matching(SEXP graph, SEXP types, SEXP weights, S
   }
   IGRAPH_FINALLY(igraph_vector_int_destroy, &c_matching);
   if (!Rf_isNull(weights)) { R_SEXP_to_vector(weights, &c_weights); }
-  c_eps=REAL(eps)[0];
+  if (Rf_xlength(eps) == 1) {
+    c_eps = REAL(eps)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(eps));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_maximum_bipartite_matching(&c_graph, (Rf_isNull(types) ? 0 : (Rf_isNull(types) ? 0 : &c_types)), &c_matching_size, &c_matching_weight, &c_matching, (Rf_isNull(weights) ? 0 : (Rf_isNull(weights) ? 0 : &c_weights)), c_eps));
 
@@ -10676,8 +12401,18 @@ SEXP R_igraph_power_law_fit(SEXP data, SEXP xmin, SEXP force_continuous) {
   SEXP r_result;
                                         /* Convert input */
   R_SEXP_to_vector(data, &c_data);
-  c_xmin=REAL(xmin)[0];
-  c_force_continuous=LOGICAL(force_continuous)[0];
+  if (Rf_xlength(xmin) == 1) {
+    c_xmin = REAL(xmin)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(xmin));
+  }
+  if (Rf_xlength(force_continuous) == 1) {
+    c_force_continuous = LOGICAL(force_continuous)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(force_continuous));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_power_law_fit(&c_data, &c_res, c_xmin, c_force_continuous));
 
@@ -10704,9 +12439,28 @@ SEXP R_igraph_sir(SEXP graph, SEXP beta, SEXP gamma, SEXP no_sim) {
   SEXP r_result;
                                         /* Convert input */
   R_SEXP_to_igraph(graph, &c_graph);
-  c_beta=REAL(beta)[0];
-  c_gamma=REAL(gamma)[0];
-  c_no_sim=(igraph_integer_t) REAL(no_sim)[0];
+  if (Rf_xlength(beta) == 1) {
+    c_beta = REAL(beta)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(beta));
+  }
+  if (Rf_xlength(gamma) == 1) {
+    c_gamma = REAL(gamma)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(gamma));
+  }
+  if (Rf_xlength(no_sim) == 1) {
+    if (((igraph_integer_t) REAL(no_sim)[0]) != REAL(no_sim)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(no_sim)[0]);
+    }
+    c_no_sim = (igraph_integer_t) REAL(no_sim)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(no_sim));
+  }
   if (0 != igraph_vector_ptr_init(&c_res, 0)) {
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
@@ -10864,7 +12618,12 @@ SEXP R_igraph_eigen_matrix(SEXP A, SEXP sA, SEXP n, SEXP algorithm, SEXP which,
                                         /* Convert input */
   R_SEXP_to_matrix(A, &c_A);
   R_SEXP_to_sparsemat(sA, &c_sA);
-  c_n=INTEGER(n)[0];
+  if (Rf_xlength(n) == 1) {
+    c_n = INTEGER(n)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(n));
+  }
   c_algorithm=REAL(algorithm)[0];
   R_SEXP_to_igraph_eigen_which(which, &c_which);
   R_SEXP_to_igraph_arpack_options(options, &c_options);
@@ -10927,7 +12686,12 @@ SEXP R_igraph_eigen_matrix_symmetric(SEXP A, SEXP sA, SEXP n, SEXP algorithm, SE
                                         /* Convert input */
   R_SEXP_to_matrix(A, &c_A);
   R_SEXP_to_sparsemat(sA, &c_sA);
-  c_n=INTEGER(n)[0];
+  if (Rf_xlength(n) == 1) {
+    c_n = INTEGER(n)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(n));
+  }
   c_algorithm=REAL(algorithm)[0];
   R_SEXP_to_igraph_eigen_which(which, &c_which);
   R_SEXP_to_igraph_arpack_options(options, &c_options);
@@ -10978,7 +12742,16 @@ SEXP R_igraph_solve_lsap(SEXP c, SEXP n) {
   SEXP r_result;
                                         /* Convert input */
   R_SEXP_to_matrix(c, &c_c);
-  c_n=(igraph_integer_t) REAL(n)[0];
+  if (Rf_xlength(n) == 1) {
+    if (((igraph_integer_t) REAL(n)[0]) != REAL(n)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(n)[0]);
+    }
+    c_n = (igraph_integer_t) REAL(n)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(n));
+  }
   if (0 != igraph_vector_int_init(&c_p, 0)) {
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
@@ -11143,7 +12916,16 @@ SEXP R_igraph_fundamental_cycles(SEXP graph, SEXP start, SEXP bfs_cutoff, SEXP w
   if (!Rf_isNull(start)) {
     c_start = (igraph_integer_t) REAL(start)[0];
   }
-  c_bfs_cutoff=(igraph_integer_t) REAL(bfs_cutoff)[0];
+  if (Rf_xlength(bfs_cutoff) == 1) {
+    if (((igraph_integer_t) REAL(bfs_cutoff)[0]) != REAL(bfs_cutoff)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(bfs_cutoff)[0]);
+    }
+    c_bfs_cutoff = (igraph_integer_t) REAL(bfs_cutoff)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(bfs_cutoff));
+  }
   if (!Rf_isNull(weights)) { R_SEXP_to_vector(weights, &c_weights); }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_fundamental_cycles(&c_graph, &c_basis, (Rf_isNull(start) ? 0 : c_start), c_bfs_cutoff, (Rf_isNull(weights) ? 0 : &c_weights)));
@@ -11178,9 +12960,28 @@ SEXP R_igraph_minimum_cycle_basis(SEXP graph, SEXP bfs_cutoff, SEXP complete, SE
     igraph_error("", __FILE__, __LINE__, IGRAPH_ENOMEM);
   }
   IGRAPH_FINALLY(igraph_vector_int_list_destroy, &c_basis);
-  c_bfs_cutoff=(igraph_integer_t) REAL(bfs_cutoff)[0];
-  c_complete=LOGICAL(complete)[0];
-  c_use_cycle_order=LOGICAL(use_cycle_order)[0];
+  if (Rf_xlength(bfs_cutoff) == 1) {
+    if (((igraph_integer_t) REAL(bfs_cutoff)[0]) != REAL(bfs_cutoff)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(bfs_cutoff)[0]);
+    }
+    c_bfs_cutoff = (igraph_integer_t) REAL(bfs_cutoff)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(bfs_cutoff));
+  }
+  if (Rf_xlength(complete) == 1) {
+    c_complete = LOGICAL(complete)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(complete));
+  }
+  if (Rf_xlength(use_cycle_order) == 1) {
+    c_use_cycle_order = LOGICAL(use_cycle_order)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(use_cycle_order));
+  }
   if (!Rf_isNull(weights)) { R_SEXP_to_vector(weights, &c_weights); }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_minimum_cycle_basis(&c_graph, &c_basis, c_bfs_cutoff, c_complete, c_use_cycle_order, (Rf_isNull(weights) ? 0 : &c_weights)));
@@ -11410,8 +13211,22 @@ SEXP R_igraph_tree_game(SEXP n, SEXP directed, SEXP method) {
 
   SEXP r_result;
                                         /* Convert input */
-  c_n=(igraph_integer_t) REAL(n)[0];
-  c_directed=LOGICAL(directed)[0];
+  if (Rf_xlength(n) == 1) {
+    if (((igraph_integer_t) REAL(n)[0]) != REAL(n)[0]) {
+      igraph_errorf("The value %.17g is not representable as an integer.",
+                    __FILE__, __LINE__, IGRAPH_EINVAL, REAL(n)[0]);
+    }
+    c_n = (igraph_integer_t) REAL(n)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(n));
+  }
+  if (Rf_xlength(directed) == 1) {
+    c_directed = LOGICAL(directed)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(directed));
+  }
   c_method = (igraph_random_tree_t) Rf_asInteger(method);
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_tree_game(&c_graph, c_n, c_directed, c_method));
@@ -11553,7 +13368,12 @@ SEXP R_igraph_roulette_wheel_imitation(SEXP graph, SEXP vid, SEXP is_local, SEXP
                                         /* Convert input */
   R_SEXP_to_igraph(graph, &c_graph);
   c_vid = (igraph_integer_t) REAL(vid)[0];
-  c_is_local=LOGICAL(is_local)[0];
+  if (Rf_xlength(is_local) == 1) {
+    c_is_local = LOGICAL(is_local)[0]; 
+  } else {
+    igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(is_local));
+  }
   R_SEXP_to_vector(quantities, &c_quantities);
   R_SEXP_to_vector_int_copy(strategies, &c_strategies);
   IGRAPH_FINALLY(igraph_vector_int_destroy, &c_strategies);
@@ -11637,7 +13457,12 @@ SEXP R_igraph_progress(SEXP message, SEXP percent) {
   igraph_error_t c_result;
   SEXP r_result;
                                         /* Convert input */
-  c_percent=REAL(percent)[0];
+  if (Rf_xlength(percent) == 1) {
+    c_percent = REAL(percent)[0]; 
+  } else {
+  igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                  __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(percent));
+  }
                                         /* Call igraph */
   IGRAPH_R_CHECK(igraph_progress(c_message, c_percent, 0));
 
diff --git a/tools/stimulus/types-RC.yaml b/tools/stimulus/types-RC.yaml
index 1cfac8c7b7..8dca4d9a04 100644
--- a/tools/stimulus/types-RC.yaml
+++ b/tools/stimulus/types-RC.yaml
@@ -39,7 +39,17 @@ INTEGER:
         OUT: '&%C%'
         INOUT: '&%C%'
     INCONV:
-        IN: '%C%=(igraph_integer_t) REAL(%I%)[0];'
+        IN: |-
+            if (Rf_xlength(%I%) == 1) {
+              if (((igraph_integer_t) REAL(%I%)[0]) != REAL(%I%)[0]) {
+                igraph_errorf("The value %.17g is not representable as an integer.",
+                              __FILE__, __LINE__, IGRAPH_EINVAL, REAL(%I%)[0]);
+              }
+              %C% = (igraph_integer_t) REAL(%I%)[0]; 
+            } else {
+              igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                            __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(%I%));
+            }
         OUT: '%C%=0;'
     OUTCONV:
         OUT: |-
@@ -53,7 +63,13 @@ INT:
         OUT: '&%C%'
         INOUT: '&%C%'
     INCONV:
-        IN: '%C%=INTEGER(%I%)[0];'
+        IN: |-
+            if (Rf_xlength(%I%) == 1) {
+              %C% = INTEGER(%I%)[0]; 
+            } else {
+              igraph_errorf("Expecting a scalar integer but received a vector of length %zu.", 
+                            __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(%I%));
+            }
 
 CSTRING:
     CTYPE: const char*
@@ -68,8 +84,14 @@ REAL:
         IN: '%C%'
         OUT: '&%C%'
         INOUT: '&%C%'
-    INCONV:
-        IN: '%C%=REAL(%I%)[0];'
+    INCONV: 
+        IN: |-
+            if (Rf_xlength(%I%) == 1) {
+              %C% = REAL(%I%)[0]; 
+            } else {
+            igraph_errorf("Expecting a scalar real but received a vector of length %zu.", 
+                            __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(%I%));
+            }
     OUTCONV:
         OUT: |-
             PROTECT(%I%=NEW_NUMERIC(1));
@@ -82,7 +104,13 @@ BOOLEAN:
         OUT: '&%C%'
         INOUT: '&%C%'
     INCONV:
-        IN: '%C%=LOGICAL(%I%)[0];'
+        IN: |-
+            if (Rf_xlength(%I%) == 1) {
+              %C% = LOGICAL(%I%)[0]; 
+            } else {
+              igraph_errorf("Expecting a scalar logical but received a vector of length %zu.", 
+                            __FILE__, __LINE__, IGRAPH_EINVAL, (size_t) Rf_xlength(%I%));
+            }
     OUTCONV:
         OUT: |-
             PROTECT(%I%=NEW_LOGICAL(1));