theano_backend.py 文件源码

def foldr(fn, elems, initializer=None, name=None):
    """Reduce elems using fn to combine them from right to left.

    # Arguments
        fn: Callable that will be called upon each element in elems and an
            accumulator, for instance lambda acc, x: acc + x
        elems: tensor
        initializer: The first value used (elems[-1] in case of None)
        name: A string name for the foldr node in the graph

    # Returns
        Same type and shape as initializer
    """
    if initializer is None:
        initializer = elems[-1]
        elems = elems[:-1]

    # We need to change the order of the arguments because theano accepts x as
    # first parameter and accumulator as second
    fn2 = lambda x, acc: fn(acc, x)

    return theano.foldr(fn2, elems, initializer, name=name)[0]