Checking if a function exists

[Michiel]

Tyler Knott wrote:

>> I'm not quite sure how to do this, but I'm sure one of you does. I need
>> something like:
>>
>> static if ( functionExists(char[] .toString(T)) ) { ... }
>>
>> static if ( functionExists(char[] T.toString()) ) { ... }
>>
>> What is the real way to do this static check?
>>
>> Thanks!
>>
> Check out this
> (http://www.digitalmars.com/webnews/newsgroups.php?art_group=digitalmars.D.learn&article_id=6577)
> thread in digitalmars.D.learn.  It answers your question exactly.

Well, not exactly. They only check for the function name, while I also
need to check out the parameter.

And if I really want to do it right, also the return type. But I suppose
a function named toString will probably return char[], so that's less
important.

> For
> non-static member functions of classes you'll need to test against a
> reference to that class (although it doesn't need to be initialized). 
> To get the return and parameter types you can use the templates in
> std.traits (note: those templates (and DMD itself) will only reveal the
> first overload of a function; there is no way to get the parameter list
> for others).

That's too bad. Because std.string.toString is exactly the function I
want to check for (among other, self-defined toString functions). And
there are 20 such functions, all with a different parameter type.

I don't really need the whole list of parameters anyway. I only want to
know if a function with a parameter type I specify exists or not.

-- 
Michiel