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A package with lisp-like generic functions.

Project description

GF: Lisp-Like generic Functions

`gf` lets you write generic functions
`generic functions <>`_
with multi-methods, that dispatch on all their arguments:

>>> from gf import generic, method
>>> add = generic()
>>> type(add)
<type 'function'>

Lets define `add` for two integers:

>>> @method(int, int)
... def add(n0, n1):
... return n0 + n1

Lets test it:

>>> add(1, 2)

Calling `add` with instances of other types fails:

>>> add("Hello ", "World")
Traceback (most recent call last):
NotImplementedError: Generic '__main__.add' has no implementation for type(s): __builtin__.str, __builtin__.str

Of course `add` can also by defined for two strings:

>>> @method(basestring, basestring)
... def add(s0, s1):
... return s0 + s1

Now our hello world example works:

>>> add("Hello ", "World")
'Hello World'

`add` can also be defined for a string and an integer:

>>> @method(basestring, int)
... def add(s, n):
... return s + str(n)

Thus we can add a string and a number:

>>> add("You ", 2)
'You 2'


A short sketch of teh chnages done in each release.

Release 0.1.2

The following was changed in Release 0.1.2:

* Added a generic functions for :meth:`gf.Object.__call__`.
* Added a :class:`gf.go.FinalizingMixin`.
* :func:`gf.generic` now also accepts a type.
* Improved the exception information for ambiguous calls.
* Fixed some documentation glitches.

Release 0.1.1

This was the initial release.

Guido van Rossum created the core of this package. I just renamed some things
and added some convenience stuff. Thank you Guido!

© 2006 Python Software Foundation.
© 2006-2013 Gerald Klix.

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