On Friday, 16 May 2014 at 20:31:40 UTC, Phil Lavoie wrote:
The idea is to eventually be able to do something like this:
constraint InputRange(Elt) {
Elt front();
void popFront();
bool empty();
}
I have a similar idea, but I think of it as a type inference
mechanism:
@inference
template InputRange(E=Any, S=void) {
static if (is(S.front))
static if (is(E==Any)||is(E==ElementType!S)) alias InputRange =
S;
else alias InputRange = Mismatch!"element type mismatch";
else alias InputRange = Mismatch!"need `front` member";
}
Here E is optional parameter, which can be used to constrain
range element type, or may be omitted to accept any element type.
S is type of right hand expression. As a bonus, this template can
substitute type.
