Ranges, constantly frustrating

[Jesse Phillips]

On Tuesday, 11 February 2014 at 10:10:27 UTC, Regan Heath 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.
>
> R

In case the other replies weren't clear enough. A range does not 
have an index.

What do you expect 'i' to be? Is it the line number? Is it the 
index within the line where 'take' begins? Where 'take' stops?

There is a feature of foreach and tuple() which results in the 
tuple getting expanded automatically.

byLine has its own issues with reuse of the buffer, it isn't 
inherent to ranges. I haven't really used it (needed it from 
std.process), when I wanted to read a large file I went with 
wrapping std.mmap:

https://github.com/JesseKPhillips/libosm/blob/master/source/util/filerange.d