Re: how does isInputRange(T) actually work?

[Ali Çehreli via Digitalmars-d-learn]

On 04/21/2015 12:06 PM, kevin wrote:

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
     }));


... is the current implementation in Phobos. But I can't seem to
understand this syntax. What is (inout int = 0)? Why can a block follow it?

My guess is that this is declaring some sort of function and testing if
it is syntactically valid, but this is still strange to me.

I try to explain that syntax here:


http://ddili.org/ders/d.en/templates_more.html#ix_templates_more.named%20template%20constraint

Ali