Multidimensional slice

[Rafael]

On Wednesday, 19 December 2012 at 11:59:24 UTC, Nekroze wrote:
> On Wednesday, 19 December 2012 at 10:33:38 UTC, Rafael wrote:
>> On Wednesday, 19 December 2012 at 10:25:23 UTC, Rafael wrote:
>>> On Wednesday, 19 December 2012 at 10:17:28 UTC, Nekroze wrote:
>>>> On Wednesday, 19 December 2012 at 09:58:37 UTC, Rafael wrote:
>>>>> //Then I want to do something like
>>>>> x = S[0..$, 1]; //get column
>>>>> S[0..$, 2] = A[0..$, 2]; //get and set column
>>>>> auto B = A[0..10, 0..10]; //get submatrix block of matrix A
>>>>
>>>> Warning the following is my total noob opinion.
>>>>
>>>> Instead of using [0..$,2] for example, try [0..$][2] and see 
>>>> how that works out. D doesn't use multiple indexes in the 
>>>> same [] section as far as i know so give that a go.
>>>
>>> Yes, this is the first solution, that come to mind. But there 
>>> are some problems in that way. Firs of them (but not main) - 
>>> not uniform syntax. The more important: which should result 
>>> operation Matrix[0..$] in that case?
>>
>> Not uniform syntax in this case is the one simple thing:
>> A[i, j]; // get the a_ij
>> A[i][j]; // get the a_ij
>>
>> but I like a first variant!
>
> Sorry it may be my lack of knowledge or something but no one 
> else seems to be responding so i will keep trying to help as 
> best i can.
>
> What do you mean by uniform syntax? do you mean you want the 
> syntax to be the same as in other languages? because as it says 
> on the dlang page for arrays under rectangular arrays it says 
> that a[i][j] is just the way that D does it where as in c++ is 
> a[i, j] but that's just one of the differences between 
> languages that cant be avoided as far as i know.

Ok.
1) It is possible to implement multiindex access using opIndex* 
methods, moreover this is the simplest way to multiindex access 
realization. So, we have [i, j, k] notation. Next step after it - 
slices implementation and it looks logical to save the same 
notation for it: [i1..i2, j1..j2, k]. But it impossible, if I 
understand correctly.

2) On the other hand. Syntax via [i][j] leads to some overhead: 
first index access [i] must return some light accessor object 
(like range (or iterator)) which supports the index access 
operation. But using this approach it is possible to implement 
multidimensional slices. And this means, that opIndex* methods 
with multiindex are not needed.