Functional utilities

pysistence.func.flip(func)

Return a function that is equivalent to func except that it has its first two arguments reversed. For instance flip(my_function)(a, b) is equivalent to my_function(b, a).

pysistence.func.const(retval)

Return a function that will always return retval.

pysistence.func.compose(func1, *funcs)

Create a function that composes func1 and funcs from left to right. For example:

>>> from functools import partial
>>> from pysistence.func import compose
>>> rejoin = compose(str.split, partial(str.join, '-'))
>>> rejoin("This is a string")
'This-is-a-string'

pysistence.func.identity(*args)

If a single argument is given, return it. Otherwise, return a tuple of the arguments given. Example:

>>> from pysistence.func import identity
>>> identity(1)
1
>>> identity(1, 2, 3)
(1, 2, 3)
>>> identity()
()

pysistence.func.trampoline(func, *args, **kwargs)

Calls func with args and kwargs. If the result is a callable, it will call that function and repeat this process until a non-callable is returned. This can be useful to write recursive functions without blowing the stack. Example:

>>> from functools import partial
>>> from pysistence.func import trampoline
>>> def count_to_a_million(i):
...     i += 1
...     if i < 1000000:
...             return partial(count_to_a_million, i)
...     else:
...             return i
...
>>> trampoline(count_to_a_million, 1)
1000000