Ruby Matrix

When I need to use a grid-like data structure, I pick a 2 dimensional array:

arr = [
  [1, 2, 3], 
  [2, 3, 4],
  [5, 6, 7]
]

And so, whenever I need to iterate over all the values, I need a nested enumerator or I could flatten the array and then iterate.

array.each_with_index do |row, row_idx|
  row.each_with_index do |cell, col_idx|
    # do work
  end
end

The Matrix class helps here.

require 'matrix'

m = Matrix[
  [1, 2, 3],
  [2, 3, 4],
  [5, 6, 7]
]

A difference between Array, where we look up row / column with arr[row][col], we use m[row, col] with Matrix.

Because Matrix mixes in Enumerable, it exposes all the wonderful methods from that module, but each goes element by element and each_with_index gives us the cell value and the row and column position.

m.each_with_index { |cell, row, col| #...

And transforms with map are nice

m.map { |cell| cell * 2 }
# => Matrix[[2, 4, 6], [8, 10, 12], [14, 16, 18]]