maybe_python7.py

import functools


class MaybeException(Exception):
    pass


def maybe(fn):
    @functools.wraps(fn)
    def wrapper(*args, **kwargs):
        try:
            return fn(*args, **kwargs)
        except Exception:
            return None
    return wrapper


@maybe
def divide(num, den):
    return num / den


def maybe_fn(default_val, fn, maybe_val):
    if maybe_val is None:
        return default_val

    return fn(maybe_val)


def is_just(maybe_val):
    return maybe_val is not None


def is_nothing(maybe_val):
    return maybe_val is None


def from_just(maybe_val):
    if maybe_val is None:
        raise MaybeException('from_just: Nothing')

    return maybe_val


def from_maybe(default_val, maybe_val):
    return maybe_val or default_val


def list_to_maybe(lst):
    return maybe(lambda x: x[0])(lst)


def maybe_to_list(maybe_val):
    if maybe_val is None:
        return []

    return [maybe_val]

def cat_maybes(maybes_lst):
    return [mv for mv in maybes_lst if mv]


def map_maybe(map_maybe_fn, inp_lst):
    return [mv for mv in map(map_maybe_fn, inp_lst) if mv]