On Friday, 5 July 2019 at 00:54:15 UTC, Samir wrote:
Is there a cleaner way of finding the maximum value of say the third column in a multi-dimensional array than this?
int[][] p = [[1,2,3,4], [9,0,5,4], [0,6,2,1]];
writeln([p[0][2], p[1][2], p[2][2]].max);

I've tried the following
writeln([0, 1, 2].map!(p[a][2]).max);

but get an "Error: undefined identifier a" error.

I know there doesn't seem to be much of a difference between two examples but my real-world array is more complex which is why I'm looking for a more scalable option.


Hi Samir,

You may want to take a look into mir-algorithm [1] library.
It contains ndsilce package [2] to work with multidimensional data.

The following example can be run online [3]:


dependency "mir-algorithm" version="~>3.4.4"

import mir.algorithm.iteration: reduce;
import mir.ndslice: fuse, map, byDim;
import mir.utility: max;

import std.stdio: writeln;

void main()
    // create 2D matrix type of Slice!(int*, 2);
        auto matrix = [[1,2,3,4], [9,0,5,4], [0,6,2,1]].fuse;

        .byDim!1 // by columns
        .map!(c => int.min.reduce!max(c))
        .writeln; // [9, 6, 5, 4]


1. https://github.com/libmir/mir-algorithm
2. http://mir-algorithm.libmir.org/mir_ndslice.html
3. https://run.dlang.io/is/OW6zvF

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