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A package with lisp-like generic functions.

Project description

Overview

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)
3

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'

Acknowledgements

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

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