Understanding isInfinite(Range)

[Andrej Mitrovic]

Ah, you're right. Whenever I see the square brackets my brain automatically things "we're indexing something". I'll blame that on C. :p

Thanks.

Steven Schveighoffer Wrote:

> On Fri, 03 Sep 2010 11:12:29 -0400, Andrej Mitrovic  
> <andrej.mitrovich at test.com> wrote:
> 
> > I was reading about the various range templates in std.range and I found  
> > this:
> >
> > http://www.digitalmars.com/d/2.0/phobos/std_range.html#isInfinite
> >
> > Seems simple enough. But I dont understand it's implementation, this  
> > from range.d:
> >
> > template isInfinite(Range)
> > {
> >     static if (isInputRange!Range && is(char[1 + Range.empty]))
> >         enum bool isInfinite = !Range.empty;
> >     else
> >         enum bool isInfinite = false;
> > }
> >
> > What does char[1 + Range.empty] do? It looks rather cryptic..
> 
> char[1+Range.empty] is a type.  If Range.empty is a compile-time constant,  
> then this type is valid, otherwise it's not valid (the is expression  
> results to true if the argument is a valid type).
> 
> If it's valid, then Range.empty never changes.  If it never changes and  
> it's always false, then it's infinite.
> 
> -Steve