Re: [Python-Dev] Switch statement

Raymond Hettinger Thu, 15 Jun 2006 12:27:27 -0700

The optimisation of the if-elif case would then simply be to say that the
compiler can recognise if-elif chains like the one above where the RHS
of the comparisons are all hashable literals and collapse them to switch
statements.


Right (constants are usually hashable :-).

The LHS is more challenging. Given:

    if x == 1: p_one()
    elif x == 2: p_two()
    elif x == 3: p_three()
    else: p_catchall()

There is no guarantee that x is hashable. For example:

    class X:
        def __init__(self, value):
             self.value = value
        def __cmp__(self, y):
             return self.value == y
    x = X(2)

Raymond

_______________________________________________
Python-Dev mailing list
[email protected]
http://mail.python.org/mailman/listinfo/python-dev
Unsubscribe: 
http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com

Re: [Python-Dev] Switch statement

Reply via email to