On 8/17/15 6:44 PM, anonymous wrote:
On Monday, 17 August 2015 at 22:32:10 UTC, Idan Arye wrote:
On Monday, 17 August 2015 at 21:27:47 UTC, Meta wrote:
[...]
At that point, couldn't you just use static if inside the body of the
template instead of using template constraints?
No. Consider this: http://dpaste.dzfl.pl/a014aeba6e68. The having two
foo templates is illegal(though it'll only show when you try to
instantiate foo), because each of them covers all options for T. When
T is neither int nor float, the foo *function* in the first template
is not defined, but the *foo* template is still there.
The idea is to have only one template:
template foo(T) {
static if (is(T == int)) {
...
} else static if (is(T == float)) {
...
} else static if (is(T == char)) {
...
} else static if (is(T == bool)) {
...
}
}
What if there is another foo template that handles double? possibly in
another file? There would be a conflict for instantiation.
That is why we use template constraints instead of static if -- the
constraint disqualifies the instantiation.
-Steve
