std.string.join & co. do a character-by-character copy because hasLength!string is false

[Vladimir Panteleev]

On Fri, 27 May 2011 21:29:10 +0300, KennyTM~ <kennytm at gmail.com> wrote:

> On May 28, 11 02:05, Vladimir Panteleev wrote:
>> Why hasLength!string is false:
>> https://github.com/D-Programming-Language/phobos/blob/96941d5384a5fee302df/std/range.d#L767
>>
>>
>> Would it make sense to introduce a hasOpaqueLength oslt. to fix this?
>>
>
> You mean std.array.join? The 2-argument overload has specialization for  
> strings  
> (https://github.com/D-Programming-Language/phobos/blob/master/std/array.d#L966).
>
>      static if (isForwardRange!RoR && hasLength!RoR
>              && (hasLength!(ElementType!RoR) ||  
> isSomeString!(ElementType!RoR))
> // ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>              && hasLength!R)
>
> It doesn't exist for the 1-argument overload though.

Thanks! But it looks like the 2-argument overload is broken too. It  
doesn't check if the separator is a string, so that branch isn't taken for  
join(string[], string). In fact, it doesn't work at all when the second  
argument is an iterator with length:

C:\Soft\dmd2\src\phobos\std\array.d(778): Error: template  
std.algorithm.copy(Range1,Range2) if (isInputRange!(Range1) &&  
isOutputRange!(Range2,ElementType!(Range1))) does not match any function  
template declaration
C:\Soft\dmd2\src\phobos\std\array.d(778): Error: template  
std.algorithm.copy(Range1,Range2) if (isInputRange!(Range1) &&  
isOutputRange!(Range2,ElementType!(Range1))) cannot deduce template  
function from argument types !()(Result,string)
test26.d(9): Error: template instance  
std.array.join!(string[],Map!(result,string)) error instantiating

Program:

import std.array;
import std.algorithm;

void main()
{
	string[] arr;
	string sep;

	join(arr, map!"a"(sep));
}


-- 
Best regards,
  Vladimir                            mailto:vladimir at thecybershadow.net