On Tuesday, 12 December 2023 at 15:20:23 UTC, Paul Backus wrote:
Because of autodecoding [1], slices of char and wchar are
treated by Phobos as bidirectional ranges of dchar. (They are
not random-access ranges because UTF-8 and UTF-16 are
variable-length encodings.)
To work around this, use std.utf.byChar:
import std.utf: byChar;
foreach (perm; as.byChar.permutations)
writeln(perm);
[1]
http://ddili.org/ders/d.en/ranges.html#ix_ranges.decoding,%20automatic
ah, many thanks, I never would have figured that out.
But unfortunately, the code shown now prints 120 lines of:
baaaa
120 being suspiciously equal to 5!. The documentation[2] seems to
imply that this should be:
baaaa
abaaa
...
When I replace the char[] with int[] [2, 1, 1, 1, 1], it produces
120 lines of random arrangements of the input, but mostly just
repeating the input.
Clearly it's doing permutations of a separate array of [0, 1, 2,
3, 4], and then replacing each index with the element at that
index (or the equivalent) but it's not even doing that right.
I'll play with nextPermutation. I suspect it would have to be
implemented the way that I'm expecting.
[2]
https://dlang.org/library/std/algorithm/iteration/permutations.html
