[PEAK] Re: Generic functions in Python

Phillip J. Eby pje at telecommunity.com
Thu Feb 7 16:59:59 EST 2008

At 03:33 PM 2/7/2008 -0600, Aaron Lebo wrote:
>I really was wanting to use generic functions in Python, but I'm 
>unsure which library is the best to use. There is RuleDispatch and 
>then also PEAK-Rules (?). Which would you suggest using? I'm looking 
>to use something with similar power to Common Lisp generic 
>functions, will either library fit that requirement?

Both exceed Common Lisp's power, as CL doesn't do predicate dispatch 
(or even symmetric multi-dispatch).  They don't include all of the CL 
method combinations, but in either case you can write any method 
combination you need with a bit of work.

>Also, are there performance/portability issues I should be aware of 
>(does this or can this run on Jython/IronPython in the future)?

RuleDispatch is capable of operating in a pure-Python mode and IIRC 
does not rely on any hacks that wouldn't be (in principle) portable 
to Jython or IronPython.  RuleDispatch, however, isn't going to be 
supported in the future, except perhaps as a compatibility API around 

PEAK-Rules is 100% pure Python, but isn't as portable since the 
engine system relies on CPython bytecode manipulation.  It'd be quite 
possible, however, to make it more portable, e.g. by adding engines 
that do source code generation, CLR/JVM bytecode generation, 
etc.  But at the moment I don't have any plans to do that.

>Finally, I was looking around for docs, do those come with the source?

RuleDispatch doesn't really have any, except for a couple of Wiki 
pages.  PEAK-Rules has massive amounts of internal documentation as 
.txt files with the source, but doesn't have any beginning user docs 
at the moment.

>Sorry for all the questions! Thanks for your help and all the work 
>you've done.

In future, please send all emails regarding my open source software 
to the PEAK mailing list or distutils-SIG (for setuptools). 

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