http://d.puremagic.com/issues/show_bug.cgi?id=9878

           Summary: std.algorithm.cartesianProduct results order
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: minor
          Priority: P2
         Component: Phobos
        AssignedTo: nobody@puremagic.com
        ReportedBy: bearophile_hugs@eml.cc


--- Comment #0 from bearophile_hugs@eml.cc 2013-04-04 19:48:53 PDT ---
This is an example of Python usage of its product() function:

>>> from itertools import product
>>> list(product([0, 1], repeat=3))
[(0, 0, 0), (0, 0, 1), (0, 1, 0), (0, 1, 1), (1, 0, 0), (1, 0, 1), (1, 1, 0),
(1, 1, 1)]



This is a similar usage of Phobos std.algorithm.cartesianProduct:


import std.stdio, std.algorithm, std.string, std.conv, std.array;
void main() {
    auto bits = [0, 1];
    auto p = cartesianProduct(bits, bits, bits);
    p.text.replace("Tuple!(int, int, int)", "").writeln;
}


Its output:

[(0, 0, 0), (1, 0, 0), (0, 1, 0), (1, 1, 0), (0, 0, 1), (1, 0, 1), (0, 1, 1),
(1, 1, 1)]

I'd like cartesianProduct() to give its results in the same order as Python. If you see in Python the results are like the binary numbers:

000
001
010
011
100
101
110
111

I think this is a more natural and more useful order.

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--- Comment #1 from hsteoh@quickfur.ath.cx 2013-05-27 19:56:52 PDT ---
https://github.com/D-Programming-Language/phobos/pull/1314

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thelastmammoth@gmail.com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |thelastmammoth@gmail.com


--- Comment #2 from thelastmammoth@gmail.com 2013-05-27 21:28:17 PDT ---
(In reply to comment #1)
> https://github.com/D-Programming-Language/phobos/pull/1314

Please see: http://forum.dlang.org/post/mailman.283.1369715080.13711.digitalmars-d@puremagic.com where I suggest to give a template parameter to specify lexicographic/antilexicographic, along with depth first/breadth first.

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--- Comment #3 from bearophile_hugs@eml.cc 2013-05-28 02:56:25 PDT ---
(In reply to comment #2)

> where I suggest to give a template parameter to specify lexicographic/antilexicographic, along with depth first/breadth first.

If you want to add an option to specify the ordering, then I'd like the order discussed here (lexicographic) to be the default one, because it's the most commonly needed by me, and it's what I expect when I port Python code to D.

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