Multidimensional slice

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

On Sat, Aug 09, 2014 at 08:43:32PM +0000, Remi Thebault via Digitalmars-d-learn wrote:
> Hello D-community
> 
> Sorry to dig an old post, but I have the exact same need.
> I have C++ background and I started to use D a few days ago only
> (a pity I didn't start sooner!)
> 
> My needs are mostly around numerical calculations. I have a safe
> and efficient matrix type in C++ that I am porting to D.
> 
> Implementation is really easier, no doubt.
> I have coded slicing following this page
> http://dlang.org/operatoroverloading.html#Slice
> but the code doesn't compile.
[...]
>      slice opSlice(uint from, uint to)
>      {
>          return slice(from, to-from);
>      }

You need opSlice to take a compile-time integer argument to determine
which dimension you're slicing. Something like this:

       slice opSlice(size_t dim)(uint from, uint to)
       {
	   // In this case it's not necessary to actually use dim, but
	   // the lowering does translate to opSlice!0(...). Defining
	   // opSlice without dim will only work for 1D arrays.
           return slice(from, to-from);
       }


[...]
>      // m3 should refer to the same slice as m2
>      auto m3 = m[2..5, 2..4];   // <- compiler syntax error is here
[...]

I think you need 2.066 or later to get this to work. After adding
(size_t dim) to opSlice, your code compiles fine with git HEAD.


T

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