#!/usr/bin/env python
"""
	Determine whether or not a string is the
	same forward and backwards.
"""

def reversible(line):
	""" Return true if line is reversible. """
	print "   debug: line = '%s'" % line
	if len(line)<=1: 
		return True
	elif line[0] != line[-1]:
		return False
	else:
		return reversible(line[1:-1])

def clean(line):
	""" Return a 'cleaned' line: lowercase and a-z only."""
	result = []
	line = line.lower()
	for char in line:
		if ord('a') <= ord(char) <= ord('z'): 
			result.append(char)
	return ''.join(result)

def interactive():
	running = True
	print "-- Is it reversible? --"
	print "   Type 'quit' or '' to exit."
	while (running):
		line = raw_input(" Input a line of text: ")
		line = clean(line)
		if line == "" or line == "quit":
			running = False
		else:
			if reversible(line):
				print " Yup."
			else:
				print " Nope."

interactive()