Chars sorting and copies

[Kagamin]

bearophile Wrote:

> I have many strings and I want to use as associative array kay a sorted concat of two strings (it's a signature of the two strings):
> 
> 
> import std.algorithm;
> void main() {
>     string a = "red";
>     string b = "green";
>     int[string] aa;
>     //aa[(a ~ b).sort] = 1;
>     //aa[(a ~ b).sort.idup] = 1;
>     aa[(a.dup ~ b.dup).sort.idup] = 1;
> }
> 
> I think the first way used to work, the second way was recently forbidden (and you can't use char[] as associative array key). The third way now works, but array.sort will go away.
> 
> So do you know what's a copy-minimizing (and possibly short) way to perform this, in future?
> 
> Bye and thank you,
> bearophile

http://www.d-programming-language.org/phobos/std_algorithm.html#setUnion ?