Feature converter ints doubles (#201)

Author: sbearrows

NEWS.md

@@ -1,7 +1,9 @@
 # cpp11 (development version)
+* added `as_double()` and `as_integer()` method to coerce integers to doubles and doubles to integers to doubles (@sbearrows, #46)
 * Removed redundant `.Call calls` in cpp11.cpp file (@sbearrows, #170)
 * Allow cpp11 decorators of the form `cpp11::linking_to` (@sbearrows, #193)
 
+
 # cpp11 0.3.1
 
 * Fix stringop-truncation warning from generated wrapping code.

cpp11test/src/test-doubles.cpp

@@ -1,6 +1,7 @@
 #include <testthat.h>
 #include <cstring>
 #include "cpp11/doubles.hpp"
+#include "cpp11/integers.hpp"
 #include "cpp11/sexp.hpp"
 #include "cpp11/strings.hpp"
 
@@ -359,6 +360,26 @@ context("doubles-C++") {
     expect_true(cpp11::is_na(y));
   }
 
+  test_that("as_doubles(integers)") {
+    cpp11::writable::integers y;
+    y.push_back(10);
+    y.push_back(13616);
+    y.push_back(124);
+    y.push_back(899);
+    cpp11::doubles i(cpp11::as_doubles(y));
+
+    expect_true(i[0] == 10);
+    expect_true(i[1] == 13616);
+    expect_true(i[2] == 124);
+    expect_true(i[3] == 899);
+    expect_true(TYPEOF(i) == REALSXP);
+
+    cpp11::writable::strings e;
+    e.push_back("a");
+    e.push_back("b");
+    expect_error(cpp11::as_doubles(e));
+  }
+
   test_that("doubles operator[] and at") {
     cpp11::doubles x(Rf_allocVector(REALSXP, 2));
     REAL(x)[0] = 1;

cpp11test/src/test-integers.cpp

@@ -1,8 +1,41 @@
 #include <testthat.h>
 #include "Rversion.h"
+#include "cpp11/doubles.hpp"
 #include "cpp11/integers.hpp"
+#include "cpp11/strings.hpp"
 
 context("integers-C++") {
+  test_that("as_integers(doubles)") {
+    // TYPEOF(x) == INTSXP
+    cpp11::writable::doubles y;
+    y.push_back(10.00);
+    cpp11::writable::integers i(cpp11::as_integers(y));
+    expect_true(i[0] == 10);
+    expect_true(TYPEOF(i) == INTSXP);
+
+    cpp11::writable::doubles x;
+    x.push_back(10.01);
+    expect_error(cpp11::as_integers(x));
+
+    cpp11::writable::strings e;
+    e.push_back("a");
+    e.push_back("b");
+    expect_error(cpp11::as_integers(e));
+
+    cpp11::writable::doubles z;
+    z.push_back(10);
+    z.push_back(1000);
+    z.push_back(100000);
+    z.push_back(100000.00);
+
+    cpp11::writable::integers t((cpp11::as_integers(z)));
+    expect_true(t[0] == 10);
+    expect_true(t[1] == 1000);
+    expect_true(t[2] == 100000);
+    expect_true(t[3] == 100000);
+    expect_true(TYPEOF(t) == INTSXP);
+  }
+
   test_that("integers.push_back()") {
     cpp11::writable::integers x;
     x.push_back(1);

inst/include/cpp11/doubles.hpp

@@ -131,6 +131,26 @@ typedef r_vector<double> doubles;
 
 }  // namespace writable
 
+typedef r_vector<int> integers;
+
+inline doubles as_doubles(sexp x) {
+  if (TYPEOF(x) == REALSXP) {
+    return as_cpp<doubles>(x);
+  }
+
+  else if (TYPEOF(x) == INTSXP) {
+    integers xn = as_cpp<integers>(x);
+    size_t len = xn.size();
+    writable::doubles ret;
+    for (size_t i = 0; i < len; ++i) {
+      ret.push_back(static_cast<double>(xn[i]));
+    }
+    return ret;
+  }
+
+  throw type_error(INTSXP, TYPEOF(x));
+}
+
 template <>
 inline double na() {
   return NA_REAL;

inst/include/cpp11/integers.hpp

@@ -141,4 +141,29 @@ inline int na() {
   return NA_INTEGER;
 }
 
+// forward declaration
+
+typedef r_vector<double> doubles;
+
+inline integers as_integers(sexp x) {
+  if (TYPEOF(x) == INTSXP) {
+    return as_cpp<integers>(x);
+  } else if (TYPEOF(x) == REALSXP) {
+    doubles xn = as_cpp<doubles>(x);
+    size_t len = (xn.size());
+    writable::integers ret = writable::integers(len);
+    for (size_t i = 0; i < len; ++i) {
+      double el = xn[i];
+      if (!is_convertable_without_loss_to_integer(el)) {
+        throw std::runtime_error("All elements must be integer-like");
+      }
+      ret[i] = (static_cast<int>(el));
+    }
+
+    return ret;
+  }
+
+  throw type_error(REALSXP, TYPEOF(x));
+}
+
 }  // namespace cpp11