#!/usr/bin/python
#
# relchange.py
#
# Computes the relative change between two numbers.
#
# Copyright (c) 2006 Marco Colombo
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# See http://www.gnu.org/licenses/gpl.txt for a copy of the license.
#

import sys

#
# main
#
def main(argv = None):

    # change argv if we are not running from the interactive prompt
    if argv is None:
        argv = sys.argv

    # check if we have the correct number of arguments
    if len(argv) != 3:
        print "Usage: relchange.py <first> <second>"
        return 1
    
    # take the file names from the command line
    try:
        first  = float(argv[1])
        second = float(argv[2])
    except ValueError:
        print "The values must be numeric."
        return 2

    # compute and print the relative change
    res = (second - first)/first * 100
    print "%4.1f%%" % res


if __name__ == "__main__":
    sys.exit(main())