Pattern matching in Python

http://monkey.org/~marius/pattern-matching-in-python.html

by mariusae • 17 years ago

38 6 17 years ago

ulf• 17 years ago

This adds a neat Prolog-angle to the whole language. Cant wait to see if someone actually makes a complete prolog-module out of this.

silentbicycle2• 17 years ago

While I don't have direct experience with either of these (I just googled for "python prolog backtracking"), you could probably do just as well in idiomatic Python using generators:

  * http://codespeak.net/pypy/extradoc/paper/prolog-in-python.pdf
  * http://mail.python.org/pipermail/python-list/2005-October/348485.html

I think Peter Norvig has written about this, too.

alextp• 17 years ago

I'm not sure, I don't think python semantics would support implicit backtracking.

silentbicycle2• 17 years ago

While pattern matching is one of my favorite things about OCaml, I'm not sure this fits well in Python. A big part of Python is trying to keep the language from being all things to all people and accumulating esoteric cruft, especially in the syntax. If I ran the zoo, I would have probably chosen a slightly different subset of features for Python, but I have a lot of respect for Guido's intent.

Also, doing anything by overloading arithmetic operators for a semantically unrelated purpose tends to be pretty disharmonious with the rest of the language. The only exception I can think of is Lua's LPEG (http://www.inf.puc-rio.br/~roberto/lpeg/lpeg.html), but that's a specific sub-language that tends to be clearly isolated to grammars; in practice, it's usually as distinct as using * within regular expression strings.

erlanger• 17 years ago

That is terribly un-Pythonic, and a poor imitation to boot. Neat proof of concept though.

paulgb• 17 years ago

Cool.

I wrote some pattern matching code myself for python a few months back just for fun. It was extremely unpythonic, but a fun exercise. For comparison, here's my code:

http://github.com/paulgb/python-pattern-matching/tree/master

Pattern matching in Python

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