method

each_with_index

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What's this?

each_with_index(which = :all) public

Same as #each, but the row index and column index in addition to the element

Matrix[ [1,2], [3,4] ].each_with_index do |e, row, col|
  puts "#{e} at #{row}, #{col}"
end
  # => Prints:
  #    1 at 0, 0
  #    2 at 0, 1
  #    3 at 1, 0
  #    4 at 1, 1

Show source

# File lib/matrix.rb, line 451
  def each_with_index(which = :all) # :yield: e, row, column
    return to_enum :each_with_index, which unless block_given?
    last = column_count - 1
    case which
    when :all
      @rows.each_with_index do |row, row_index|
        row.each_with_index do |e, col_index|
          yield e, row_index, col_index
        end
      end
    when :diagonal
      @rows.each_with_index do |row, row_index|
        yield row.fetch(row_index){return self}, row_index, row_index
      end
    when :off_diagonal
      @rows.each_with_index do |row, row_index|
        column_count.times do |col_index|
          yield row[col_index], row_index, col_index unless row_index == col_index
        end
      end
    when :lower
      @rows.each_with_index do |row, row_index|
        0.upto([row_index, last].min) do |col_index|
          yield row[col_index], row_index, col_index
        end
      end
    when :strict_lower
      @rows.each_with_index do |row, row_index|
        [row_index, column_count].min.times do |col_index|
          yield row[col_index], row_index, col_index
        end
      end
    when :strict_upper
      @rows.each_with_index do |row, row_index|
        (row_index+1).upto(last) do |col_index|
          yield row[col_index], row_index, col_index
        end
      end
    when :upper
      @rows.each_with_index do |row, row_index|
        row_index.upto(last) do |col_index|
          yield row[col_index], row_index, col_index
        end
      end
    else
      raise ArgumentError, "expected #{which.inspect} to be one of :all, :diagonal, :off_diagonal, :lower, :strict_lower, :strict_upper or :upper"
    end
    self
  end

each_with_index

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