libgap-api: add NEW_RANGE and GAP_NewRange

src/exprs.c

@@ -980,13 +980,7 @@ static Obj EvalRangeExpr(Expr expr)
              ErrorQuit("Range: the length of a range must be a small integer",
                         0, 0);
         }
-        if ( 0 < inc )
-            range = NEW_RANGE_SSORT();
-        else
-            range = NEW_RANGE_NSORT();
-        SET_LEN_RANGE( range, (high-low) / inc + 1 );
-        SET_LOW_RANGE( range, low );
-        SET_INC_RANGE( range, inc );
+        range = NEW_RANGE((high - low) / inc + 1, low, inc);
     }
 
     /* return the range                                                    */

src/intrprtr.c

@@ -2221,13 +2221,7 @@ void IntrListExprEnd(
                            0, 0);
             }
 
-            if ( 0 < inc )
-                list = NEW_RANGE_SSORT();
-            else
-                list = NEW_RANGE_NSORT();
-            SET_LEN_RANGE( list, (high-low) / inc + 1 );
-            SET_LOW_RANGE( list, low );
-            SET_INC_RANGE( list, inc );
+            list = NEW_RANGE((high - low) / inc + 1, low, inc);
         }
 
         /* push the list again                                             */

src/libgap-api.c

@@ -33,6 +33,7 @@
 #include "opers.h"
 #include "plist.h"
 #include "precord.h"
+#include "range.h"
 #include "records.h"
 #include "streams.h"
 #include "stringobj.h"
@@ -416,6 +417,22 @@ Obj GAP_NewPlist(Int capacity)
     return NEW_PLIST(T_PLIST_EMPTY, capacity);
 }
 
+static BOOL fitsInIntObj(Int i)
+{
+    return INT_INTOBJ_MIN <= i && i <= INT_INTOBJ_MAX;
+}
+
+Obj GAP_NewRange(Int len, Int low, Int inc)
+{
+    if (!inc) return GAP_Fail;
+    if (!fitsInIntObj(len)) return GAP_Fail;
+    if (!fitsInIntObj(low)) return GAP_Fail;
+    if (!fitsInIntObj(inc)) return GAP_Fail;
+    Int high = low + (len - 1) * inc;
+    if (!fitsInIntObj(high)) return GAP_Fail;
+    return NEW_RANGE(len, low, inc);
+}
+
 
 ////
 //// matrix obj

src/libgap-api.h

@@ -379,6 +379,15 @@ Obj GAP_ElmList(Obj list, UInt pos);
 // Returns a new empty plain list with capacity <capacity>
 Obj GAP_NewPlist(Int capacity);
 
+// Returns a new range with <len> elements, starting at <low>, and proceeding
+// in increments of <inc>. So the final element in the range will be equal to
+// <high> := <low> + <inc> * (<len> - 1).
+//
+// Note that <inc> must be non-zero, and all three arguments as
+// well as the value <high> must fit into a GAP small integer.
+// If any of these conditions is violated, then GAP_Fail is returned.
+Obj GAP_NewRange(Int len, Int low, Int inc);
+
 
 ////
 //// matrix obj

src/range.c

@@ -97,6 +97,22 @@ static Obj TypeRangeSSort(Obj list)
 }
 
 
+Obj NEW_RANGE(Int len, Int low, Int inc)
+{
+    Obj range;
+
+    if (0 < inc)
+        range = NewBag(T_RANGE_SSORT, 3 * sizeof(Obj));
+    else
+        range = NewBag(T_RANGE_NSORT, 3 * sizeof(Obj));
+    SET_LEN_RANGE(range, len);
+    SET_LOW_RANGE(range, low);
+    SET_INC_RANGE(range, inc);
+
+    return range;
+}
+
+
 #if !defined(USE_THREADSAFE_COPYING)
 
 /****************************************************************************
@@ -394,14 +410,8 @@ static Obj ElmsRange(Obj list, Obj poss)
         }
 
         /* make the result range                                           */
-        if ( 0 < inc * GET_INC_RANGE(list) )
-            elms = NEW_RANGE_SSORT();
-        else
-            elms = NEW_RANGE_NSORT();
-        SET_LEN_RANGE( elms, lenPoss );
-        SET_LOW_RANGE( elms, INT_INTOBJ( GET_ELM_RANGE( list, pos ) ) );
-        SET_INC_RANGE( elms, inc * GET_INC_RANGE( list ) );
-
+        inc *= GET_INC_RANGE(list);
+        elms = NEW_RANGE(lenPoss, INT_INTOBJ( GET_ELM_RANGE( list, pos ) ), inc);
     }
 
     return elms;
@@ -765,10 +775,7 @@ Obj Range2Check (
         SET_ELM_PLIST( range, 1, first );
     }
     else {
-        range = NEW_RANGE_SSORT();
-        SET_LEN_RANGE( range, (l-f) + 1 );
-        SET_LOW_RANGE( range, f );
-        SET_INC_RANGE( range, 1 );
+        range = NEW_RANGE((l-f) + 1, f, 1);
     }
     return range;
 }
@@ -805,13 +812,7 @@ Obj Range3Check (
         SET_ELM_PLIST( range, 1, first );
     }
     else {
-        if ( 0 < i )
-            range = NEW_RANGE_SSORT();
-        else
-            range = NEW_RANGE_NSORT();
-        SET_LEN_RANGE( range, (l - f) / i + 1 );
-        SET_LOW_RANGE( range, f );
-        SET_INC_RANGE( range, i );
+        range = NEW_RANGE((l - f) / i + 1, f, i);
     }
     return range;
 }

src/range.h

@@ -31,18 +31,10 @@
 **
 *F  NEW_RANGE() . . . . . . . . . . . . . . . . . . . . . .  make a new range
 **
-**  'NEW_RANGE' returns a new range.  Note that  you must set the length, the
-**  low value, and the increment before you can use the range.
+**  'NEW_RANGE' returns a new range.
 */
-EXPORT_INLINE Obj NEW_RANGE_NSORT(void)
-{
-    return NewBag(T_RANGE_NSORT, 3 * sizeof(Obj));
-}
+Obj NEW_RANGE(Int len, Int low, Int inc);
 
-EXPORT_INLINE Obj NEW_RANGE_SSORT(void)
-{
-    return NewBag(T_RANGE_SSORT, 3 * sizeof(Obj));
-}
 
 /****************************************************************************
 **

tst/testlibgap/api.c

@@ -59,6 +59,42 @@ void lists(void)
     assert(ret == 0);
 }
 
+void ranges(void)
+{
+    const int len = 5;
+    int i;
+    Obj r, val;
+
+    r = GAP_NewRange(len, 1, 1); // [1..5]
+    assert(GAP_IsList(r));
+    assert(GAP_LenList(r) == len);
+    for (i = 1; i <= len; ++i) {
+        val = GAP_ElmList(r, i);
+        assert(GAP_IsSmallInt(val));
+        assert(GAP_EQ(val, GAP_NewObjIntFromInt(i)));
+    }
+
+    r = GAP_NewRange(len, 1, 3); // [1,4..16]
+    assert(GAP_IsList(r));
+    assert(GAP_LenList(r) == len);
+    for (i = 1; i <= len; ++i) {
+        val = GAP_ElmList(r, i);
+        assert(GAP_IsSmallInt(val));
+        assert(GAP_EQ(val, GAP_NewObjIntFromInt(1 + (i-1) * 3)));
+    }
+
+
+    r = GAP_NewRange(len, 10, -2); // [10,8..2]
+    assert(GAP_IsList(r));
+    assert(GAP_LenList(r) == len);
+    for (i = 1; i <= len; ++i) {
+        val = GAP_ElmList(r, i);
+        assert(GAP_IsSmallInt(val));
+        assert(GAP_EQ(val, GAP_NewObjIntFromInt(10 - 2*(i-1))));
+    }
+
+}
+
 void matrices(void)
 {
     Obj mat, val, row, ret;
@@ -213,6 +249,10 @@ int main(int argc, char ** argv)
     lists();
     printf("success\n");
 
+    printf("# Testing ranges... ");
+    ranges();
+    printf("success\n");
+
     printf("# Testing matrices... ");
     matrices();
     printf("success\n");

tst/testlibgap/api.expect

@@ -2,6 +2,7 @@
 # Testing strings... success
 # Testing records... success
 # Testing lists... success
+# Testing ranges... success
 # Testing matrices... success
 # Testing integers... success
 # Testing operations... success