[Issue 7128] Cartesian product of ranges

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=7128

--- Comment #21 from bearophile_hugs at eml.cc ---
A third optional argument can be a "buffer" array, if it's large enough (as
much as the "power" argument or larger), it gets used to make cartesianPower a
@nogc function:

cartesianPower!false([0, 1], 2, buffer)

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