cannot sort an array of char

[via Digitalmars-d-learn]

On Thursday, 6 November 2014 at 10:52:32 UTC, Ivan Kazmenko wrote:
> On Wednesday, 5 November 2014 at 13:34:05 UTC, Marc Schütz 
> wrote:
>> On Wednesday, 5 November 2014 at 12:54:03 UTC, Ivan Kazmenko 
>> wrote:
>>> Hi!
>>>
>>> This gives an error (cannot deduce template function from 
>>> argument types):
>>>
>>> -----
>>> import std.algorithm;
>>> void main () {
>>> 	char [] c;
>>> 	sort (c);
>>> }
>>> -----
>>>
>>> Why is "char []" so special that it can't be sorted?
>>>
>>> For example, if I know the array contains only ASCII 
>>> characters, sorting it sounds no different to sorting an "int 
>>> []".
>>
>> Hmm... this doesn't work either:
>>
>>    import std.algorithm;
>>    import std.utf;
>>    void main () {
>>        char [] c;
>>        sort (c.byCodeUnit);
>>    }
>>
>> But IMO it should.
>
> So, you imply that to use a char array as a RandomAccessRange, 
> I have to use byCodeUnit? (and it should work, but doesn't?)
>

Yes. H.S. Teoh has already submitted a PR to fix it.

> Fine, but how does one learn that except by asking here?  
> Googling did not produce meaningful results for me.
>
> For example, isRandomAccessRange[0] states the problem:
> -----
> Although char[] and wchar[] (as well as their qualified 
> versions including string and wstring) are arrays, 
> isRandomAccessRange yields false for them because they use 
> variable-length encodings (UTF-8 and UTF-16 respectively). 
> These types are bidirectional ranges only.
> -----
> but does not offer a solution.  If (when) byCodeUnit does 
> really provide a random-access range, it would be desirable to 
> have it linked where the problem is stated.
>
> [0] http://dlang.org/phobos/std_range.html#.isRandomAccessRange

I agree. But how should it be implemented? We would have to 
modify algorithms that require an RA range to also accept char[], 
but then print an error message with the suggestion to use 
byCodeUnit. I think that's not practicable. Any better ideas?