strap.py 文件源码

def pieces_under_over(path, segs_to_points, xings):
    """Produce all the pieces of the path, with a bool indicating if each leads to under or over."""
    pieces = list(path_pieces(path, segs_to_points))
    for i, piece in enumerate(pieces):
        xing = xings.get(piece[-1])
        if xing is None:
            continue
        if xing.under is not None:
            over = (xing.under != path)
        else:
            assert xing.over is not None
            over = (xing.over == path)
        ou = [over, not over]
        if i % 2:
            ou = ou[::-1]
        break
    else:
        ou = [True, False]

    yield from zip(pieces, itertools.cycle(ou))