foreach with a default range

[Jonathan M Davis via Digitalmars-d]

On Thursday, 11 June 2015 at 13:09:21 UTC, Steven Schveighoffer 
wrote:
> On 6/11/15 8:54 AM, Dmitry Olshansky wrote:
>> On 11-Jun-2015 15:22, Steven Schveighoffer wrote:
>>> On 6/11/15 4:24 AM, Dmitry Olshansky wrote:
>>>
>>>> Already works. Just define opSlice for container that 
>>>> returns a range
>>>> and then:
>>>>
>>>> foreach(elem; container) {}
>>>>
>>>> is lowered to:
>>>>
>>>> foreach(elem; container[]) {}
>>>>
>>>
>>> I think you want to do opIndex which takes no parameters.
>>
>> Ehm. How is being more logical or what is the reason?
>>
>>> opSlice is no
>>> longer supposed to be used that way (though it still works 
>>> for backwards
>>> compatibility).
>>
>> Now that's the real news. Me thinks slice it on foreach was 
>> added
>> speicfically for std.container back in 2012. Where the docs 
>> for the
>> later change (well, both of them for that matter)?
>>
>
> See this thread, was news to me too: 
> http://forum.dlang.org/thread/luadir$t0g$1@digitalmars.com#post-mailman.669.1410325102.5783.digitalmars-d-learn:40puremagic.com
>
> The rationale was in order to support multi-dimensional slicing.

Yes, but isn't it specifically for the case where you're using 
multi-dimensional arrays and _not_ the general case? Certainly, 
that's what I understood when talking with John Colvin about how 
the multi-dimensional array support works. It sounded like the 
compiler started looking for other stuff to be implemented if you 
defined opIndex with no parameters, whereas it doesn't if opSlice 
with no parameters is defined. So, I wouldn't start using opIndex 
that way without really understanding what's going on there in 
detail.

Regardless, from an idiomatic perspective, it makes far more 
sense to be implementing opSlice with empty parameters than 
opIndex simply based on what the operators are for. So, if you 
can do both, I'd argue that you should be using opSlice with no 
parameters if you don't need whatever the heck is going on with 
multi-dimensional arrays.

- Jonathan M Davis