# RecursivePalindrome.py
#
# Description: Calls the Palindrome function and prints 
#                 That’s a palindrome!
#              when the function returns True and
#                 That’s no palindrome!  
#              when then function returns False.
#              The program terminates when the user presses Enter
#              which creates an empty string.
#              Iterative and Recursive implementations.
#
# Author: Anne Lavergne
# Date: March 4 2024

# Palindrome iterative function
def palindrome(aWord):
    """Returns True if 'aWord' is a palindrome and False it is not."""

    # Compute the index of the last character
    reverseIndex = len(aWord)-1
    
    # Consider each character of first half of aWord
    for anIndex in range(0,len(aWord)//2):
        
        # If this character and it matching character 
        # at the end of aWord or not the same character ...
        if aWord[anIndex] != aWord[reverseIndex]:
            # Then aWord is not a palindrome
            return False
        
        # Otherwise, consider the next pair of characters
        reverseIndex -= 1

    # If we reached this point in the function
    # then aWord is a palindrome
    return True


# Palindrome recursive function
def palindromeR(aWord):
    """Returns True if 'aWord' is a palindrome and False it is not."""

    # Base Case
    if len(aWord) <= 1:
        return True

    # Recursive Case
    # Check the first and last characters
    if aWord[0] != aWord[-1]: # aWord[len(aWord)-1]
        return False

    return palindromeR(aWord[1:-1])

                       

# ***Main part of my program

# Ask the user for a word, empty string to stop
theWord = input("Please input a word or press Enter to stop: ")
while theWord:
    # Call the iterative version of the function palindrome
    if palindrome(theWord):
        print("Calling palindrome(): That's a palindrome!")
    else:
        print("Calling palindrome(): That's no palindrome!")

    # Call the recursive version of the function palindrome
    if palindromeR(theWord):
        print("Calling palindromeR(): That's a palindrome!")
    else:
        print("Calling palindromeR(): That's no palindrome!")
        
    # Ask the user for a word, empty string to stop
    theWord = input("Please input a word or press Enter to stop: ")

print("Bye!")