• Tobias Pankrath (11/11) Jul 24 2011 I needed a small script for a project of mine and hacked one in python.
• Dmitry Olshansky (15/26) Jul 24 2011 Apparently, this overload of replace has 3 parameters: input, what to

Tobias Pankrath <tobias pankrath.net> writes:

I needed a small script for a project of mine and hacked one in python. 
Since I want to learn some D, I tried to convert it. Took me a bit longer 
than I thought, because I got delayed by this lovely error message:

Error: template instance ambiguous template declaration 
std.array.replace(R1,R2,R3) if (isDynamicArray!(R1) && isForwardRange!(R2) 
&& isForwardRange!(R3) && (hasLength!(R3) || isSomeString!(R3))) and 
std.regex.replace(Range,Engine,String) if (is(Unqual!(Engine) == Regex!
(Unqual!(typeof(Range.init[0])))))

Took me a while do understand it, but it seems that I've got a name 
collision. What I don't understand is, why is the compiler unable to 
tell two functions, one with two parameter and one with three, apart?

Dmitry Olshansky <dmitry.olsh gmail.com> writes:

On 24.07.2011 20:46, Tobias Pankrath wrote:
 I needed a small script for a project of mine and hacked one in python.
 Since I want to learn some D, I tried to convert it. Took me a bit longer
 than I thought, because I got delayed by this lovely error message:

 Error: template instance ambiguous template declaration
 std.array.replace(R1,R2,R3) if (isDynamicArray!(R1)&&  isForwardRange!(R2)
 &&  isForwardRange!(R3)&&  (hasLength!(R3) || isSomeString!(R3))) and
 std.regex.replace(Range,Engine,String) if (is(Unqual!(Engine) == Regex!
 (Unqual!(typeof(Range.init[0])))))

 Took me a while do understand it, but it seems that I've got a name
 collision. What I don't understand is, why is the compiler unable to
 tell two functions, one with two parameter and one with three, apart?

Apparently, this overload of replace has 3 parameters: input, what to 
replace  and a replacement. It searches and replaces all occurrences.

I've hit the same issue while implementing a replacement for std.regex, 
the underlying problem I think is that
std.array.replace has a way too lousy template constraint. According to 
source it checks only if it's input is a range or string,  but if it has 
compatible type is *not* checked.

Now with std.regex since RegexMatch is ForwardRange it's of course 
matches, but element type is string/wstring/dstring, while I suppose 
std.array in this case would need element type of dchar.

It hadn't occurred to me that somebody will hit this anytime soon, so 
now I might roll out a pull request sooner :)

-- 
Dmitry Olshansky