On Thursday, 30 July 2015 at 19:12:27 UTC, jmh530 wrote:
On Thursday, 30 July 2015 at 10:40:59 UTC, Atila Neves wrote:
[...]
I might be overthinking this.
You would still need to define something for checkInputRange.
Are you thinking something simple like
template checkInputRange(R)
{
enum bool checkInputRange = isInputRange!R;
}
In this case, the error message is still referring to
checkInputRange instead of isInputRange. So the user would
still need to refer to that and see what that functions
conditions are. Alternately, you could write checkInputRange to
provide the user information about which functions are not
implemented (like no pop, no popFront, no empty). That seems
more difficult, but would be convenient for the user.
The benefit of something simple like
template satisfies_alt(alias Constraint, R) {
static assert(Constraint!R);
}
is that at least you don't have to write extra functions. You
only need isInputRange. The downside is that the error message
references Constraint instead of isInputRange. That's less
intuitive.
Check the out the PR I mentioned:
https://github.com/D-Programming-Language/phobos/pull/3520
The idea would be to define a similar check function for each
constraint. Without it, you don't get the nice error messages.
Atila
