Multiple Dispatch
=================

|Build Status| |Coverage Status| |Version Status|

A relatively sane approach to multiple dispatch in Python.

This implementation of multiple dispatch is efficient, mostly complete,
performs static analysis to avoid conflicts, and provides optional namespace
support.  It looks good too.

See the documentation at https://multiple-dispatch.readthedocs.io/


Example
-------

.. code-block:: python

   >>> from multipledispatch import dispatch

   >>> @dispatch(int, int)
   ... def add(x, y):
   ...     return x + y

   >>> @dispatch(object, object)
   ... def add(x, y):
   ...     return "%s + %s" % (x, y)

   >>> add(1, 2)
   3

   >>> add(1, 'hello')
   '1 + hello'

What this does
--------------

-  Dispatches on all non-keyword arguments

-  Supports inheritance

-  Supports instance methods

-  Supports union types, e.g. ``(int, float)``

-  Supports builtin abstract classes, e.g. ``Iterator, Number, ...``

-  Caches for fast repeated lookup

-  Identifies possible ambiguities at function definition time

-  Provides hints to resolve ambiguities when they occur

-  Supports namespaces with optional keyword arguments

-  Supports variadic dispatch

What this doesn't do
--------------------

-  Diagonal dispatch

.. code-block:: python

   a = arbitrary_type()
   @dispatch(a, a)
   def are_same_type(x, y):
       return True

-  Efficient update: The addition of a new signature requires a full resolve of
   the whole function.  This becomes troublesome after you get to a few hundred
   type signatures.


Installation and Dependencies
-----------------------------

``multipledispatch`` is on the Python Package Index (PyPI):

::

    pip install multipledispatch

It is Pure-Python and depends only on the standard library.
It is a light weight dependency.


License
-------

New BSD. See `License file`_.


Links
-----

-  `Five-minute Multimethods in Python by Guido`_
-  `multimethods package on PyPI`_
-  `singledispatch in Python 3.4's functools`_
-  `Clojure Protocols`_
-  `Julia methods docs`_
-  `Karpinksi notebook: *The Design Impact of Multiple Dispatch*`_
-  `Wikipedia article`_
-  `PEP 3124 - *Overloading, Generic Functions, Interfaces, and Adaptation*`_


.. _`Five-minute Multimethods in Python by Guido`:
  http://www.artima.com/weblogs/viewpost.jsp?thread=101605
.. _`multimethods package on PyPI`:
  https://pypi.python.org/pypi/multimethods
.. _`singledispatch in Python 3.4's functools`:
  http://docs.python.org/3.4/library/functools.html#functools.singledispatch
.. _`Clojure Protocols`:
  http://clojure.org/protocols
.. _`Julia methods docs`:
  https://docs.julialang.org/en/v1/manual/methods/
.. _`Karpinksi notebook: *The Design Impact of Multiple Dispatch*`:
  http://nbviewer.ipython.org/gist/StefanKarpinski/b8fe9dbb36c1427b9f22
.. _`Wikipedia article`:
  http://en.wikipedia.org/wiki/Multiple_dispatch
.. _`PEP 3124 - *Overloading, Generic Functions, Interfaces, and Adaptation*`:
  http://legacy.python.org/dev/peps/pep-3124/

.. |Build Status| image:: https://travis-ci.org/mrocklin/multipledispatch.svg
   :target: https://travis-ci.org/mrocklin/multipledispatch
.. |Version Status| image:: https://pypip.in/v/multipledispatch/badge.svg
   :target: https://img.shields.io/pypi/v/multipledispatch.svg
.. |Coverage Status| image:: https://coveralls.io/repos/mrocklin/multipledispatch/badge.svg
   :target: https://coveralls.io/r/mrocklin/multipledispatch
.. _License file: https://github.com/mrocklin/multipledispatch/blob/master/LICENSE.txt