Another stab at a "switch/case" construct (for Python 3000):

[Ken Peek]

"Bjorn Pettersen" <BPettersen at NAREX.com> wrote in message news:<mailman.1017454367.25440.python-list at python.org>...
> > From: Steven Majewski [mailto:sdm7g at Virginia.EDU]
> > 
> > On Fri, 29 Mar 2002, Bjorn Pettersen wrote:
> > 
> > > > From: Steve Lamb [mailto:grey at despair.dmiyu.org]
> > > >
> > > > its called a directory pointing to functions = {'case':closed}
> > > >
> > > >     I do not believe that any language which can have a hash
> > > > of function pointers has any business with a case statement.
> > >
> > > But that only works when all the functions in all the branches take
>  the
> > > same number and types of arguments -- hardly the general case.
> > >
> > 
> > table = {}
> > 
> > table[key] = func, (args,...)
> > ...
> > 
> > def doit( k ):
> > 	return table[k][0]( *table[k][1] )
> 
> Point taken, but is this an argument for or against the match/switch
> statement <wink>?
> 
> Personally, I don't think it's worth adding a match statement unless we
> can have ML style pattern matching...
> 
> Not-sure-what-a-good-Pythonic-spelling-would-be-though'ly y'rs
> -- bjorn

Since we are no longer forcing only literals to be used (which would
allow for compile time optimizations), I don't think there would be
anything to stop you from allowing function calls (or other
expressions) in the parameter list of a clause, which would allow you
to do some pretty intricate calculations.  This WOULD however redefine
the way lists are parsed, and _I_ don't like that:

branchon MyObject:
    [123, 456, "hello", [], (), xyz-abc, 42*etc, MyFunc(MyObject)]:
        # do some stuff
        # do some more stuff

    ["I want a branchon construct", "(and more whining)"]:
        # do some stuff
        # do some more stuff
        fallthrough           # USEFUL a LOT!
    [MyOtherObject, (1,2,3), [4,5,6]]:
        # do some stuff
        # do some more stuff

    else:
        # no matching clauses, so:
        # do some stuff
        # do some more stuff

def MyFunc(x):
    # test object "x" for all kinds of things,
    # and return "x" if you want a match,
    # else return something guaranteed to
    # fail, like (x,none)
    if x_is_a_match:
        return x
    else
        return (x,none)

=====================

This would be clear and readable.  Use your imagination-- FEEL THE
POWER of this construct (to make more readable code)...

I-am-not-trying-to-impress-you-with-my-python-knowledge'ly yours,
--Ken Peek

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