Which of the op(Index) operators is responsible for enabling this kind of syntax?
Would it be possible to get it work with UFCS or would I have to wrap the array?

On Sunday, May 29, 2016 07:14:12 ParticlePeter via Digitalmars-d-learn wrote:
> Which of the op(Index) operators is responsible for enabling this
> kind of syntax?
> Would it be possible to get it work with UFCS or would I have to
> wrap the array?

std.container.array.Array works with foreach via ranges.

foreach(e; myContainer)
{
}

gets lowered to

foreach(e; myContainer[])
{
}

which in turn gets lowered to something like

for(auto r = myContainer[]; !r.empty; r.popFront())
{
    auto e = r.front;
}

Ranges do not support indices with foreach, and that's why you're not able to get the index with foreach and Array. However, if you use std.range.lockstep, you can wrap a range to get indices with foreach. e.g.

foreach(i, e; lockstep(myContainer[]))
{
}

http://dlang.org/phobos/std_range.html#.lockstep

- Jonathan M Davis

On Sunday, 29 May 2016 at 09:07:07 UTC, Jonathan M Davis wrote:
> On Sunday, May 29, 2016 07:14:12 ParticlePeter via Digitalmars-d-learn wrote:
>> [...]
>
> std.container.array.Array works with foreach via ranges.
>
> foreach(e; myContainer)
> {
> }
>
> gets lowered to
>
> foreach(e; myContainer[])
> {
> }
>
> which in turn gets lowered to something like
>
> for(auto r = myContainer[]; !r.empty; r.popFront())
> {
>     auto e = r.front;
> }
>
> Ranges do not support indices with foreach, and that's why you're not able to get the index with foreach and Array. However, if you use std.range.lockstep, you can wrap a range to get indices with foreach. e.g.
>
> foreach(i, e; lockstep(myContainer[]))
> {
> }
>
> http://dlang.org/phobos/std_range.html#.lockstep
>
> - Jonathan M Davis

I'd say that std.range.enumerate is more indicative of intent:

http://dlang.org/phobos/std_range.html#enumerate

On Sunday, 29 May 2016 at 09:07:07 UTC, Jonathan M Davis wrote:
> On Sunday, May 29, 2016 07:14:12 ParticlePeter via Digitalmars-d-learn wrote:
>> Which of the op(Index) operators is responsible for enabling this
>> kind of syntax?
>> Would it be possible to get it work with UFCS or would I have to
>> wrap the array?
>
> std.container.array.Array works with foreach via ranges.
>
> foreach(e; myContainer)
> {
> }
>
> gets lowered to
>
> foreach(e; myContainer[])
> {
> }
>
> which in turn gets lowered to something like
>
> for(auto r = myContainer[]; !r.empty; r.popFront())
> {
>     auto e = r.front;
> }
>
> Ranges do not support indices with foreach, and that's why you're not able to get the index with foreach and Array. However, if you use std.range.lockstep, you can wrap a range to get indices with foreach. e.g.
>
> foreach(i, e; lockstep(myContainer[]))
> {
> }
>
> http://dlang.org/phobos/std_range.html#.lockstep
>
> - Jonathan M Davis


Thanks, due to your answer I found a way which is even better for me. I pimped the Array containers with some UFCS functions anyway, one of them returns the array data as a slice and this works nicely with that foreach variant as well

auto data( T )( Array!T array )  {
    if( array.length == 0 ) return null;
    return (&array.front())[ 0..array.length ];
}

// this works now
foreach( i, a; someArrayContainer.data ) { ... }

- PP