foreach seems to work with opIndex()

[H. S. Teoh via Digitalmars-d-learn]

On Sat, Feb 06, 2016 at 03:11:22PM +0000, ZombineDev via Digitalmars-d-learn wrote:
> On Saturday, 6 February 2016 at 15:02:16 UTC, H. S. Teoh wrote:
> >On Sat, Feb 06, 2016 at 02:43:52PM +0000, Tofu Ninja via
> >Digitalmars-d-learn wrote:
> >>Foreach seems to work if there is an opIndex() with no arguments
> >>that returns a range interface, is this documented? I can't seem to
> >>find anything that say this is supposed to happen. I am not really
> >>complaining, its nice, but I just didnt really expect it because I
> >>feel like I remember this being an error some time ago.
> >
> >Not really sure, but opIndex() with no arguments is supposed to be
> >the current way of implement the [] slicing operator for user-defined
> >types.  I'm not sure when foreach started supporting that, but it's
> >certainly a nice thing!
> >
> >
> >T
> 
> I thought that opSlice() was supposed to be that operator. At least
> this is what's used in std.container (e.g.
> http://dlang.org/phobos/std_container_array.html#.Array.opSlice).

That's the old use of opSlice(), which is still supported for backward
compatibility. The new use of opSlice, after Kenji's multidimensional
array PR, is to translate x..y notation into a type that opIndex can
understand. Namely, this:

	x[1, 2..3, 4, 5..6]

is translated into:

	x.opIndex(1, x.opSlice(2,3), 4, x.opSlice(5,6))


T

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