# Copyright (c) Meta Platforms, Inc. and affiliates.
# All rights reserved.
#
# This source code is licensed under the BSD-style license found in the
# LICENSE file in the root directory of this source tree.

# pyre-unsafe

from typing import Sequence, Tuple, Union

import torch


"""
Some functions which depend on PyTorch or Python versions.
"""


def meshgrid_ij(
    *A: Union[torch.Tensor, Sequence[torch.Tensor]],
) -> Tuple[torch.Tensor, ...]:  # pragma: no cover
    """
    Like torch.meshgrid was before PyTorch 1.10.0, i.e. with indexing set to ij
    """
    if (
        # pyre-fixme[16]: Callable `meshgrid` has no attribute `__kwdefaults__`.
        torch.meshgrid.__kwdefaults__ is not None
        and "indexing" in torch.meshgrid.__kwdefaults__
    ):
        # PyTorch >= 1.10.0
        # pyre-fixme[6]: For 1st param expected `Union[List[Tensor], Tensor]` but
        #  got `Union[Sequence[Tensor], Tensor]`.
        return torch.meshgrid(*A, indexing="ij")
    # pyre-fixme[6]: For 1st param expected `Union[List[Tensor], Tensor]` but got
    #  `Union[Sequence[Tensor], Tensor]`.
    return torch.meshgrid(*A)


def prod(iterable, *, start=1):
    """
    Like math.prod in Python 3.8 and later.
    """
    for i in iterable:
        start *= i
    return start