Now the pattern matching is more interesting, but again, I'd need to see a proposed syntax for Python before I could begin to consider it. If I understand it properly, pattern matching in Haskell relies primarily on Haskell's excellent typing system, which is absent in Python.
There's no real need for special syntax in Python - an appropriate tuple subclass will do the trick quite nicely:
class pattern(tuple):
ignore = object()
def __new__(cls, *args):
return tuple.__new__(cls, args)
def __hash__(self):
raise NotImplementedError
def __eq__(self, other):
if len(self) != len(other):
return False
for item, other_item in zip(self, other):
if item is pattern.ignore:
continue
if item != other_item:
return False
return TruePy> x = (1, 2, 3) Py> print x == pattern(1, 2, 3) True Py> print x == pattern(1, pattern.ignore, pattern.ignore) True Py> print x == pattern(1, pattern.ignore, 3) True Py> print x == pattern(2, pattern.ignore, pattern.ignore) False Py> print x == pattern(1) False
It's not usable in a dict-based switch statement, obviously, but it's perfectly compatible with the current if/elif idiom.
Cheers, Nick.
--
Nick Coghlan | [EMAIL PROTECTED] | Brisbane, Australia
---------------------------------------------------------------
http://boredomandlaziness.skystorm.net
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