Hi,
I'm implementing some template checks on some types I'm using in
a project, and went to phobos for some indications on how to use
them.
In std.range, I see this construct quite a bit:
template isInputRange(R)
{
enum bool isInputRange = is(typeof(
(inout int = 0)
{
R r = R.init; // can define a range object
if (r.empty) {} // can test for empty
r.popFront(); // can invoke popFront()
auto h = r.front; // can get the front of the range
}));
}
Can anyone explain the:
is(typeof(
(inout int = 0) {}
);
section to me?
It looks very....hacky.
I see 3 distinct parts playing a role in my confusion:
A) The 'is' keyword. What does it do when you have is(expression);
B) typeof( expression ); whats this doing? Particularly when the
expression its acting on is a closure that returns nothing? (at
least as far as I can see)
C) The closure expression:
(inout int = 0) {
// Check to see if I can do InputRangy stuff...
}
Why is there a need for that inout int = 0 clause at the start of
it?
Sorry for the long question!
Thanks,
Colin
