std.range.iota enhancement: supporting more types (AKA issue 10762)

[Jakob Ovrum]

On Tuesday, 24 December 2013 at 11:47:12 UTC, Francesco Cattoglio 
wrote:
> Correct, but there's no way to compute "back" with less than 
> O(n) complexity, unless division by increment is available. 
> (Actually, I think we can achieve O(log n) with multiplication 
> alone, but I think it might be lots of work with very little 
> benefits)
> I should have specified better: we need to provide `back', and 
> Andrei suggested that no primitive should be more than complex 
> than O(1).

Implement `back` is really trivial.

Simplified example:
---
auto iota(T)(T start, T end)
{
     static struct Result
     {
         T start, end;

         bool empty() @property { return start == end; }
         T front() @property { return start; }
         void popFront() { ++start; }
         T back() @property { return end; }
         void popBack() { --end; }
         // etc
     }

     return Result(start, --end);
}
---