__author__="brock"
__date__ ="$Feb 15, 2011 10:41:43 AM$"

class CompareAndSwapRegister:
    "CompareAndSwap class"
    def __init__(self):
        self.value = 0
    def CompareAndSwap(self, oldval, newval):
        presval = self.value
        if (presval == oldval):
            self.value = newval
        return presval
    def __str__(self):
        return str(self.value)