We have awesome way for creating slices like:

    a = new int[5];
    int[] b = a[0..2];

But what about if I have 2D array and I don't want to go vertical. Something like :

int[3][3] matrix = [
    [ 1, 2, 3 ],
    [ 4, 5, 6 ],
    [ 7, 8, 9 ]
];

I believe I can use std.range function "RoundRobin"(or maybe it won't work with 2D array directly) for having a good looking vertical slice which will have 1,4,7 or 2,5,8 or 3,6,9 in my example above.

And what if I want to go diagonal like 1,5,9 or 3,5,7 in the example above. Is there a good solution in std without using for loops?

I have one more requirement for fulfilling the task that I working on. This slices do not have to be the same size as the array. For example in the example above slice size could have 2 instead of 3. In this case I need to have slices like 1,5;2,6;4,8;5,9 ... and so on for diagonal case.

Erdem

Ps: Converting the 2D array to 1D array is possible in my case.

On Saturday, 22 July 2017 at 20:55:06 UTC, kerdemdemir wrote:
> And what if I want to go diagonal like 1,5,9 or 3,5,7 in the example above. Is there a good solution in std without using for loops?

I suggest using an actual matrix type for tasks like this. I don't know about diagonal slicing, but the implementation here at least provides accessors for both rows and columns.

https://github.com/pineapplemachine/mach.d/blob/master/mach/math/matrix.d

On 22.07.2017 22:55, kerdemdemir wrote:
> We have awesome way for creating slices like:
> 
>      a = new int[5];
>      int[] b = a[0..2];
> 
> But what about if I have 2D array and I don't want to go vertical. Something like :
> 
> int[3][3] matrix = [
>      [ 1, 2, 3 ],
>      [ 4, 5, 6 ],
>      [ 7, 8, 9 ]
> ];
> 
> I believe I can use std.range function "RoundRobin"(or maybe it won't work with 2D array directly) for having a good looking vertical slice which will have 1,4,7 or 2,5,8 or 3,6,9 in my example above.
> 
> And what if I want to go diagonal like 1,5,9 or 3,5,7 in the example above. Is there a good solution in std without using for loops?
> 
> I have one more requirement for fulfilling the task that I working on. This slices do not have to be the same size as the array. For example in the example above slice size could have 2 instead of 3. In this case I need to have slices like 1,5;2,6;4,8;5,9 ... and so on for diagonal case.
> 
> Erdem
> 
> Ps: Converting the 2D array to 1D array is possible in my case.


horizontal: matrix[i][j..j+k]
vertical:   matrix[i..i+k].map!(x=>x[j])
diagonal 1: iota(k).map!(x=>matrix[i+x][j+x])
diagonal 2: iota(k).map!(x=>matrix[i+x][j-x])

On Saturday, 22 July 2017 at 20:55:06 UTC, kerdemdemir wrote:
> We have awesome way for creating slices like:
>
>     a = new int[5];
>     int[] b = a[0..2];
>
> But what about if I have 2D array and I don't want to go vertical. Something like :
>
> int[3][3] matrix = [
>     [ 1, 2, 3 ],
>     [ 4, 5, 6 ],
>     [ 7, 8, 9 ]
> ];
>
> I believe I can use std.range function "RoundRobin"(or maybe it won't work with 2D array directly) for having a good looking vertical slice which will have 1,4,7 or 2,5,8 or 3,6,9 in my example above.
>
> And what if I want to go diagonal like 1,5,9 or 3,5,7 in the example above. Is there a good solution in std without using for loops?
>
> I have one more requirement for fulfilling the task that I working on. This slices do not have to be the same size as the array. For example in the example above slice size could have 2 instead of 3. In this case I need to have slices like 1,5;2,6;4,8;5,9 ... and so on for diagonal case.
>
> Erdem
>
> Ps: Converting the 2D array to 1D array is possible in my case.

Hello Erdem,

You may want to use mir-algorithm DUB package. It is a D tensor library.
https://github.com/libmir/mir-algorithm

import mir.ndslice;

auto slice = matrix[0].ptr.sliced(3, 3);
auto row = matrix[0];
auto col = matrix[0 .. $, 0];

A lot of examples with diagonal and sub-diagonals can be found here
http://docs.algorithm.dlang.io/latest/mir_ndslice_topology.html#.diagonal

Best,
Ilya