This repository has been archived by the owner. It is now read-only.
An experiment to use infix operators in Python
Branch: master
Clone or download
Fetching latest commit…
Cannot retrieve the latest commit at this time.
Permalink
Type Name Latest commit message Commit time
Failed to load latest commit information.
.gitignore
.travis.yml
README.rst
infix.py
setup.py
tox.ini

README.rst

Infix

Latest PyPI version Travis build status

This project is an unmaintained experiment. Don't use it for production code.

A decorator that allows functions to be used as infix functions.

Infix operators are created and applied as such, and do not stop the function from being called normally:

>>> from infix import shift_infix as infix
...
>>> @infix
... def plus(a, b):
...     return a + b
...
>>> print(40 <<plus>> 2)
42
>>> print(plus(5, 5))
10

Variant syntaxes

Multiple infix syntaxes are provided by the infix module:

>>> @and_infix
... def is_before(a, b):
...     return a < b
...
>>> print(1 &is_before& 5)
True

>>> @or_infix
... def minus(a, b):
...     return a - b
...
>>> print(1 |minus| 2)
-1

>>> @xor_infix
... def until(start, stop):
...     return range(start, stop)
...
>>> print(list(1 ^until^ 10))
[1, 2, 3, 4, 5, 6, 7, 8, 9]

>>> @pow_infix
... def pow(a, b):
...     return a**b
...
>>> print(3 **pow** 2)
9

>>> dpow = div_infix(pow)
>>> print(3 /dpow/ 2)
9

Custom syntaxes

Python has a large set of operators than could be overridden to provide the infix syntax, so instead of providing them all a make_infix function is provided. To use it, pass the names of the operatorsyou want to support:

>>> @make_infix('mod','pow','rshift')
... def until(start, stop):
...     return list(range(start, stop))
>>> print(1 %until% 3)
[1, 2]
>>> print(2 <<until>> 4)
[2, 3]
>>> print(5 **until** 8)
[5, 6, 7]
>>> print(until(10,12))
[10, 11]
.. versionadded:: 1.2

The old custom_infix is still supported. It takes two parameters, the names of the left and right operator functions, though only the first is important:

>>> @custom_infix('__rmod__', '__mod__')
... def ate(a, b):
...     return (a == 7 and b == 9)
...
>>> print(7 %ate% 9)
True
>>> print(6 %ate% 7)
False

The left function should be a right operand, and the right functions should be a left operand.

You should be careful to avoid using operands that the objects your functions will take may provide themselves (as the initial right operand is only called if the previous object does not provide for that operand).

Binding

The library now uses a binding feature to generate a temporary object halfway through the process. That means that half expressions now work:

>>> 3**pow
<pow_lbind: Waiting for right side>
.. versionadded:: 1.2

Example: Currying

One possible use is in curring functions in Python. You can easily define a curry function:

>>> from functools import partial
>>> curry = or_infix(partial)
>>> def volume(x, y, z):
...    return x * y * z
>>> tot = volume |curry| 2 |curry| 3 |curry| 4
>>> tot()
24

Compatibility

Works on all major Python versions (2.6, 2.7, 3.2, 3.3, 3.4).

Tests

The tests in this README files are run using doctest. To run the tests, run ''python infix.py'' - alternatively, use tox to run the tests on all compatible Python versions.

Licence

Copyright (C) 2013 Sam Clements

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.