# Copyright (C) 2015 VIB/BEG/UGent - Tim Diels <timdiels.m@gmail.com>
#
# This file is part of Chicken Turtle Util.
#
# Chicken Turtle Util is free software: you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# Chicken Turtle Util is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public License
# along with Chicken Turtle Util. If not, see <http://www.gnu.org/licenses/>.
'''
Function manipulation, like functools. Contains only `compose`, compose functions.
'''
from functools import reduce as reduce
[docs]def compose(*functions):
'''
Compose functions
Like the ``o`` operator in math.
Parameters
----------
functions : collection(any -> any)
Collection of one or more functions to compose.
Returns
-------
any -> any
Function composed of `functions`
Raises
------
ValueError
When ``len(functions) < 1``
Examples
--------
``compose(f1, f2)`` is equivalent to ``f1 o f2``, or to ``lambda x: f1(f2(x))``
'''
if not functions:
raise ValueError('Must supply at least one function to `compose`')
apply = lambda x, y: y(x)
return lambda x: reduce(apply, reversed(functions), x)