On Wednesday, 4 October 2023 at 01:46:42 UTC, Joel wrote:
I think the if without static is still static, since it's part
of the function name part, or so (outside of the curly bracket
scope).
You can't have regular if-statements inside templates. Regular
if-statements are checked at runtime but templates only exist at
compile-time.
The way to write a *template constraint*—which is what you want,
and uses the `if` keyword—is thus:
```d
struct List(T)
if(__traits(isIntegral, T)){
auto addUp()
//(Add numbers)
}
}
```
Notice that the curly brace for the template comes after the
template constraint, and that there are only 2 curly braces
rather than the 3 from your example.
If the statement in the template constraint
(`__traits(isIntegral, T)`) evaluates false at compile-time, then
you will get a compiler error saying that the instantiation
doesn't match the template constraints.
