D2 Short list -- opSlice

[Lars T. Kyllingstad]

Don wrote:
> Andrei Alexandrescu wrote:
>> We're entering the finale of D2 and I want to keep a short list of 
>> things that must be done and integrated in the release. It is clearly 
>> understood by all of us that there are many things that could and 
>> probably should be done.
>>
>> 1. Currently Walter and Don are diligently fixing the problems marked 
>> on the current manuscript.
>>
>> 2. User-defined operators must be revamped.
> 
> Should opIndex and opSlice be merged?
> This would be simpler, and would allow multi-dimensional slicing.

Yes, please. :)


> Probably the simplest way to do this would be to use fixed length arrays 
>  of length 2 for slices.
> So, for example, if the indices are integers, then
> opIndex(int x) { } is the 1-D index, and
> opIndex(int[2] x) {} is a slice from x[0] to x[1],
> which exactly corresponding to the current opSlice(x[0]..x[1]).
> 
> Since fixed-length arrays are now passed by value (yay!) this would be 
> just as efficient as the current method. It'd be simple to implement.
> 
> Downsides: (1) Arguably not terribly intuitive.
> [...]

I think this is the only way to do it, and I don't see why it's less 
intuitive than anything else. If it helps, you can always define

   alias size_t[2] slice_t;

(or something similar) in object.d.

   // Submatrix slice
   real opIndex(slice_t rows, slice_t cols) { ... }

Doesn't look bad at all.

-Lars