## digitalmars.D.learn - Best syntax for a diagonal and vertical slice

- kerdemdemir (24/24) Jul 22 2017 We have awesome way for creating slices like:
- pineapple (5/8) Jul 24 2017 I suggest using an actual matrix type for tasks like this. I
- Timon Gehr (5/34) Jul 24 2017 horizontal: matrix[i][j..j+k]
- Ilya Yaroshenko (14/38) Aug 25 2017 Hello Erdem,

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.

Jul 22 2017

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

Jul 24 2017

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])

Jul 24 2017

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

Aug 25 2017