Ranges, constantly frustrating

[Steven Schveighoffer]

On Tue, 11 Feb 2014 05:10:27 -0500, Regan Heath <regan at netmail.co.nz>  
wrote:

> Things like this should "just work"..
>
> File input ...
>
> auto range = input.byLine();
> while(!range.empty)
> {
>    range.popFront();
>    foreach (i, line; range.take(4))  //Error: cannot infer argument types
>    {
>      ..etc..
>    }
>    range.popFront();
> }
>
> Tried adding 'int' and 'char[]' or 'auto' .. no dice.
>
> Can someone explain why this fails, and if this is a permanent or  
> temporary limitation of D/MD.

This is only available using opApply style iteration. Using range  
iteration does not give you this ability.

It's not a permanent limitation per se, but there is no plan at the moment  
to add multiple parameters to range iteration.

One thing that IS a limitation though: we cannot overload on return  
values. So the obvious idea of overloading front to return tuples of  
various types, would not be feasible. opApply can do that because the  
delegate is a parameter.

-Steve