def get_line x
    Error.call "Matrix::get_line : Line #{x} doesn't exist" if !x.is_a?Integer or x < 0 or x >= @lines

    return @v[x]
  end
def get_line x
    Error.call "Matrix::get_line : Line #{x} doesn't exist" if !x.is_a?Integer or x < 0 or x >= @lines

    return @v[x]
  end
== Parameters:
 y::
   Integer. It's the n° line which is extracted
 == Returns:
 Array