foreach range with index

[Luís Marques via Digitalmars-d]

On Wednesday, 14 June 2017 at 02:42:46 UTC, Luís Marques wrote:
> On Tuesday, 13 June 2017 at 21:44:43 UTC, Steven Schveighoffer 
> wrote:
>> But I think leaving the definition of the index up to the 
>> range itself is paramount -- I don't want every range to be 
>> able to have a size_t index, as that's not always what you 
>> want, and it conflicts with other items. What we may need is a 
>> smarter way to get from the type parameters at the front of 
>> the foreach to an iterable type.
>
> That's why I mentioned random access ranges, as in that case we 
> can sidestep this discussion; since foreach understands input 
> ranges, why can't foreach understand random access ones, and 
> iterate them as if they were slices, including maintaining a 
> foreach-generated index? That is, it would have nothing to do 
> with tuple unpacking. Plus, it would work transparently in the 
> cases you replace `slice` with `slice.algorithm`, where 
> algorithm maintains random-access. Instead of having to add 
> .enumerate in each place the slice (now a range) is iterated, 
> it would just work.

Hmm, I suppose that even if we have all of the good stuff of 
length, opIndex, opSlice, etc., we can't assume the indices are 
[0..length], right? But there should be some way for, say, map to 
preserve that information from the slice, the same way random 
access is preserved.