# -*- coding: utf-8 -*-
#  Copyright 2011 Takeshi KOMIYA
#
#  Licensed under the Apache License, Version 2.0 (the "License");
#  you may not use this file except in compliance with the License.
#  You may obtain a copy of the License at
#
#      http://www.apache.org/licenses/LICENSE-2.0
#
#  Unless required by applicable law or agreed to in writing, software
#  distributed under the License is distributed on an "AS IS" BASIS,
#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
#  See the License for the specific language governing permissions and
#  limitations under the License.

from itertools import cycle


def istep(seq, step=2):
    iterable = iter(seq)
    while True:
        yield [next(iterable) for _ in range(step)]


def stepslice(iterable, steps):
    iterable = iter(iterable)
    step = cycle(steps)

    while True:
        # skip (1)
        n = next(step)
        if n == 0:
            pass
        elif n == 1:
            o = next(iterable)
            yield o
            yield o
        else:
            yield next(iterable)
            for _ in range(n - 2):
                next(iterable)
            yield next(iterable)

        # skip (2)
        for _ in range(next(step)):
            next(iterable)
