#!/usr/bin/env python
#
# Author: Cimarron Taylor
# Date: July 6, 2003
# File Name: relpath.py
# Program Description: Print relative path from /a/b/c/d to /a/b/c1/d1

#
# helper functions for relative paths
#
import os

def pathsplit(p, rest=[]):
    (h,t) = os.path.split(p)
    if len(h) < 1: return [t]+rest
    if len(t) < 1: return [h]+rest
    return pathsplit(h,[t]+rest)

def commonpath(l1, l2, common=[]):
    if len(l1) < 1: return (common, l1, l2)
    if len(l2) < 1: return (common, l1, l2)
    if l1[0] != l2[0]: return (common, l1, l2)
    return commonpath(l1[1:], l2[1:], common+[l1[0]])

def relpath(p1, p2):
    (common,l1,l2) = commonpath(pathsplit(p1), pathsplit(p2))
    p = []
    if len(l1) > 0:
        p = [ '../' * len(l1) ]
    p = p + l2
    return os.path.join( *p )

def test(p1,p2):
    print "from", p1, "to", p2, " -> ", relpath(p1, p2)

if __name__ == '__main__':
    test('/a/b/c/d', '/a/b/c1/d1')