[Python-Dev] A thought on generic functions
Nick Coghlan
ncoghlan at gmail.com
Thu May 29 12:03:36 CEST 2008
Greg Ewing wrote:
> Paul Moore wrote:
>> I'd rather see a solution which addressed the
>> wider visitor use case (I think I just sprained my back bending over
>> backwards to avoid mentioning generic functions :-))
>
> Speaking of generic functions, while thinking about the
> recent discussion on proxy objects, it occurred to me
> that this is something you can do with an OO system
> that you can't do so easily with a generic function
> system. If the operations being proxied were generic
> functions rather than methods, you'd have to override
> them all individually instead of having a central point
> to catch them all.
I don't think it would actually be that much worse - something like
typetools.ProxyMixin would just involve a whole series of register calls
instead of method definitions. I wouldn't expect the total amount of
code involved to change much.
That said, a recursive flatten() implementation is indeed a problem that
generic functions are well suited to solving - have the default
implementation attempt to iterate over the passed in object yielding its
contents, yielding the object itself only if iteration fails, and then,
for the types the application wishes to consider atomic, register an
alternative implementation that just yields the object without
attempting to iterate over it.
Cheers,
Nick.
--
Nick Coghlan | ncoghlan at gmail.com | Brisbane, Australia
---------------------------------------------------------------
http://www.boredomandlaziness.org
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