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.

On Saturday, 6 February 2016 at 14:43:52 UTC, Tofu Ninja 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.

To clerify, I was doing something like

struct someStruct{
     ...
     dchar[] opIndex(){
          if(data==null) return null;
          else return data.some_array;
     }
}
...
someStruct s;
foreach(c;s) {}

I expected to need to write
foreach(c;s[]) {}

On 06.02.2016 15:43, Tofu Ninja 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.

https://issues.dlang.org/show_bug.cgi?id=14619

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

-- 
Nobody is perfect.  I am Nobody. -- pepoluan, GKC forum

On 06.02.2016 16:00, anonymous wrote:
> https://issues.dlang.org/show_bug.cgi?id=14619

Sorry, posted a bit hastily. Issue 14619 is just about a bug in the feature. The more relevant issue is number 5605:

https://issues.dlang.org/show_bug.cgi?id=5605

As far as I can tell, this is not documented on dlang.org. It should be, of course.

I personally think it's a misfeature. Explicit slicing is just two characters longer and makes it more clear what's happening.

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).

On Saturday, 6 February 2016 at 15:02:16 UTC, H. S. Teoh wrote:
> 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

It feels a little weird because none of the range functions like map support calling opIndex so you can omit the [] in foreach but not with map. Just feels inconsistent.

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

-- 
I am Ohm of Borg. Resistance is voltage over current.