Feature #17277
Updated by sawa (Tsuyoshi Sawada) over 3 years ago
Given a matrix: Currently this code seems to be counting index based on the internal array of arrays and it's not correct for the matrix which should return row and col indices ```ruby ``` matrix = Matrix[[0,2,3,4], [6,7,8,9], [1,4,5,8]] [1,4,5,8]].each.with_index { |e, index| print "#{index} " } ; puts 0 1 2 3 4 5 6 7 8 9 10 11 => nil ``` You I'm aware of the fact that you could do following and you get the row and col indices of a matrix using `Matrix#each_with_index`: correct results: ```ruby ``` matrix .each_with_index Matrix[[0,2,3,4], [6,7,8,9], [1,4,5,8]].each_with_index { |e, row, col| p [row, col] print "[#{row}, #{col}] " } ; puts [0, 0] [0, 1] [0, 2] [0, 3] [1, 0] [1, 1] [1, 2] [1, 3] [2, 0] [2, 1] [2, 2] [2, 3] => nil ``` You can even chain it `each_with_index` with other enumerators and access indices within them: ```ruby them e.g. matrix ``` .each_with_index .filter_map Matrix[[0,2,3,4], [6,7,8,9], [1,4,5,8]].each_with_index.filter_map { |e, row, col| [row, col] if e % 4 == 0} # => [[0, 0], [0, 3], [1, 2], [2, 1], [2, 3]] ``` Meanwhile, `Matrix#each` seems to iterate over the elements of the internal array, which does not look right: ```ruby matrix .each.with_index { |e, index| p index } 0 1 2 3 4 5 6 7 8 9 10 11 ``` However, I feel we should override `with_index` for `Matrix` Matrix so it returns row and col indices.