# Copyright 2014-2020 by Christopher C. Little.
# This file is part of Abydos.
#
# Abydos is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# Abydos 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 General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with Abydos. If not, see <http://www.gnu.org/licenses/>.

"""abydos.util._prod.

The util._prod module defines _prod, which computes the product of a collection
of numbers (akin to sum, but for product).
"""

from functools import reduce
from operator import mul
from typing import List, Sequence, Set, Union

__all__ = []  # type: List[str]


def _prod(nums: Union[Sequence[float], Set[float]]) -> float:
    r"""Return the product of nums.

    The product is

            .. math::

                \prod nums

    Cf. https://en.wikipedia.org/wiki/Product_(mathematics)

    Parameters
    ----------
    nums : list
        A collection (list, tuple, set, etc.) of numbers

    Returns
    -------
    numeric
        The product of a nums

    Examples
    --------
    >>> _prod([1,1,1,1])
    1
    >>> _prod((2,4,8))
    64
    >>> _prod({1,2,3,4})
    24
    >>> _prod(2**i for i in range(5))
    1024

    .. versionadded:: 0.1.0

    """
    return reduce(mul, nums, 1)


if __name__ == '__main__':
    import doctest

    doctest.testmod()
