tools.rst

xoutil.fp.tools -- High-level pure function tools

xoutil.fp.tools

Composition of several functions.

Functions are composed right to left. A composition of zero functions gives back the identity function.

Rules must be fulfilled (those inner all):

>>> x = 15
>>> f, g, h = x.__add__, x.__mul__, x.__xor__
>>> all((compose() is identity,
...
...      # identity functions are optimized
...      compose(identity, f, identity) is f,
...
...      compose(f) is f,
...      compose(g, f)(x) == g(f(x)),
...      compose(h, g, f)(x) == h(g(f(x)))))
True

If any "intermediate" function returns an instance of:

• pos_args: it's expanded as variable positional arguments to the next function.
• kw_args: it's expanded as variable keyword arguments to the next function.
• full_args: it's expanded as variable positional and keyword arguments to the next function.

The expected usage of these is not to have function return those types directly, but to use them when composing functions that return tuples and expect tuples.

identity

fst

snd

pos_args

kw_args

full_args