Jon Harrop: > I think this sort of functionality would be a welcome addition to Python.
I don't know. > Perhaps it can be written in Python? Pyparsing and beautifulsoup show that practically useful parsing modules can be done using Python alone too. Set module of Python 2.3, translated to C in Python 2.4 and improved in Python 2.5 shows that sometimes Python is fit to create prototypes that can be debugged, and whose API can be improved, and they can later translated to a faster language. But the decimal module shows that sometimes such translation can become a bit difficult. The re module shows that external modules too can be good enough compared of Perl/Ruby built-in regex syntax. Beside Python, various much faster languages may be used, like D, Pyrex, C, or your loved OCaml. Or theoretically even ShedSkin. I think D may be fit, the "Pyd" Python <-> D bridge is quite good, and it's improving. And D is reaching version 1.0. OCaml maybe can be used to produce Python compiled modules, so it can be a possibility too, but then very few people are able to maintain it, so maybe it's better to use a more common language (even D is more common, because its syntax is easy to grasp by C++ programmers). > What is the easiest way to add such functionality to Python? I think implementation language isn't the main problem. I think the definition of the purpose and API are more difficult. Mathematica allows you to define rules that let the system chose the right function (among some with the same name) according to the input pattern or the kind of input. Guido has discussed some about something similar, the multimethods. There are some ways and tricks to add such capabilities to Python, but I don't think they are fast and reliable enough for real programs. Maybe Python 3.0 will change this some. If you want just to create something like a regular engine that works on lists, that contains matching rules, rewriting rules and calls to many user-defined functions, then I think you can do it with Python (with Psyco if you want) in few lines (a really basic RE on lists can be defined in about 20 lines, maybe a good system may can be built with 2000-10000 lines), but I don't know how much useful it can be, maybe it can find some purpose (and maybe someone has already written such module). > I think that is an excellent idea. Who will pay me? ;-) I don't know, probably no one. Most people don't even know how to use such pattern matching programming paradigm. For Python it may become just an experiment. Bye, bearophile -- http://mail.python.org/mailman/listinfo/python-list
