#
# Name: CS 111 Course Staff
#
# lab3task2.py
#

#
# To debug this function, we start by observing that we get the following
# error message when we call the function:
#
#    RecursionError: maximum recursion depth exceeded in comparison
#
# This means that we're getting "infinite recursion" -- i.e., that we
# keep making recursive calls, and that we never reach the base case.
#
# When this happens, there are two common causes:
#
#   * there is a bug in the code that checks for the base case(s)
#   * there is a bug in the code that makes the recursive call, such that 
#     the inputs to the function are not being properly reduced.
#
# Looking at the function, can you see which of these is the cause?
#
# (We notice that the base case is incorrectly checking for a space,
#  rather than for an empty string.)
# 
# Once we eliminate the RecursionError, we should notice that we 
# still don't get the correct result.
#
# To help us debug, we can try putting a print statement on the first line 
# of the function to reveal what s is for every function call:
#
#     print('starting call for', s)
#
# You can also do something similar before each return statement, and
# include the value being returned. For example, here is something
# you could add before the final return statement:
#
#     print('call for', s, 'returns', num_in_rest)
#
# You should discover that this function is incorrectly adding 1
# when s[0] is a vowel, instead of when it is a consonant.
#
# Below is the fixed version:
#

def num_consonants(s):
    """ returns the number of consonants in s
        parameter: s is a string of lower-case letters
    """
    if s == '':
        return 0
    else:
        num_in_rest = num_consonants(s[1:])
        if s[0] not in 'aeiou':
            return num_in_rest + 1
        else:
            return num_in_rest