Fallback 'catch-all' template functions

[H. S. Teoh via Digitalmars-d]

On Thu, Sep 01, 2016 at 03:37:50PM +1000, Manu via Digitalmars-d wrote:
> So, consider a set of overloads:
> 
>   void f(T)(T t) if(isSomething!T) {}
>   void f(T)(T t) if(isSomethingElse!T) {}
>   void f(T)(T t) {}
> 
> I have a recurring problem where I need a fallback function like the
> bottom one, which should be used in lieu of a more precise match.
> This is obviously an ambiguous call, but this is a pattern that comes
> up an awful lot. How to do it in D?
> 
> I've asked this before, and people say:
> 
>   void f(T)(T t) if(!isSomething!T && !isSomethingElse!T) {}
> 
> Consider that more overloads are being introduced by users spread out
> across many modules that define their own kind of T; this solution is
> no good.

Here's a possible workaround:

	void f(T)(T t)
	{
		static if (isSomething!T) { ... }
		else static if (isSomethingElse!T) { ... }
		else { ... }
	}

But this won't work across modules. :-(


T

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