On Friday, 4 September 2015 at 15:52:08 UTC, Enamex wrote:
The biggest problem, I think, is that a template can has multiple 'predicates' to agree to be instantiated, but only some of them can mutually exclusive (the specialization syntax produces mutually exclusive ones, the if-constraints don't).[...] template Bar(T) { static if( is(T == int) || is(T == string) || ... ) { //stuff } else static if( stuff ) { // other stuff } else {template return; // I know my T took whatever your type was but I actually don't match, please exclude me from your list for this instance...} } [...]
On second thought, it wouldn't help as much as I'd thought with overloading problems. What we want is a 'which template has more '&&'ed expressions in its constraint?' which sounds pretty awful. I have no idea how this could work :/
Especially given that D's constraints are way more open than, say, Haskell's, in their checking; though ironically not their declaration/implementation (D is open because it checks for structural conformance of a struct instead of nominative & structural; but it's more restricted because it easily only checks for structure of the type as declared, with no way to attach recognized-to-the-constraint ad-hoc interfaces to a type like Haskell's with type-classes).
