def get_column y
    Error.call "Matrix::get_column : Column #{y} doesn't exist" if !y.is_a?Integer or y < 0 or y >= @columns

    result = []
    @lines.times do |i|
      result << @v[i][y]
    end
    return result
  end
def get_column y
    Error.call "Matrix::get_column : Column #{y} doesn't exist" if !y.is_a?Integer or y < 0 or y >= @columns

    result = []
    @lines.times do |i|
      result << @v[i][y]
    end
    return result
  end
== Parameters:
 y::
   Integer. It's the n° column which is extracted
 == Returns:
 Array