def parse_square_param(line):
    """
    Parse the line from the .eff file that contains the efficiency function
    parameters for a 'square' function
    line : the line containt the parameters, must start with 'square_param'
    """
    if not line.startswith("square_param="):
        raise ValueError("Not a valid square_param line")
    values = line.split()
    params = {'sigma': float(values.pop()),
              'm0': float(values.pop()),
              'c': float(values.pop()),
              'eff_max': float(values.pop())
              }
    return params