[Issue 7728] New: Alternative div and mod in core.bitop

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=7728

           Summary: Alternative div and mod in core.bitop
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: DMD
        AssignedTo: nobody at puremagic.com
        ReportedBy: bearophile_hugs at eml.cc


--- Comment #0 from bearophile_hugs at eml.cc 2012-03-18 06:04:33 PDT ---
When I translate Python code to D I sometimes need in D the different integer
division and the different modulo operation of Python3. They give different
results with the operands are negative:

Python2 code:

for x in xrange(-10, 1):
    print x, "", x % 3, "", x // 3


Python output:

-10  2  -4
-9  0  -3
-8  1  -3
-7  2  -3
-6  0  -2
-5  1  -2
-4  2  -2
-3  0  -1
-2  1  -1
-1  2  -1
0  0  0



D code:

import std.stdio;
void main() {
    foreach (x; -10 .. 1)
        writeln(x, "  ", x % 3, "  ", x / 3);
}


D output:

-10  -1  -3
-9  0  -3
-8  -2  -2
-7  -1  -2
-6  0  -2
-5  -2  -1
-4  -1  -1
-3  0  -1
-2  -2  0
-1  -1  0
0  0  0



So I suggest to add both simple functions to Phobos, possibly as efficient
compiler intrinsics (this means inlined asm) in core.bitop.


It seems Ada and CommonLisp have functions for both needs:
http://en.wikipedia.org/wiki/Modulo_operation

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