"""
A module with a single, non-working function.

The function in this module has a bug (in the sense that it does not satisfy
its specification). This allows us to show off debugging.

Author: Walker M. White
Date:   August 31, 2017 (Python 3 Version)
"""

def last_name_first(n):
    """
    Returns: copy of n but in the form 'last-name, first-name'
    
    Parameter n: the person's name
    Precondition: n is in the form 'first-name last-name'
    with one or more blanks between the two names no spaces
    in <first-name> or <last-name>
    """
    
    end_first = n.find(' ')
    first = n[:end_first]
    last  = n[end_first+1:]
    return last+', '+first