def triangulate(strips):
    """A generator for iterating over the faces in a set of
    strips. Degenerate triangles in strips are discarded.

    >>> triangulate([[1, 0, 1, 2, 3, 4, 5, 6]])
    [(0, 2, 1), (1, 2, 3), (2, 4, 3), (3, 4, 5), (4, 6, 5)]
    """

    triangles = []

    for strip in strips:
        if len(strip) < 3: continue # skip empty strips
        i = strip.__iter__()
        j = False
        t1, t2 = next(i), next(i)
        for k in range(2, len(strip)):
            j = not j
            t0, t1, t2 = t1, t2, next(i)
            if t0 == t1 or t1 == t2 or t2 == t0: continue
            triangles.append((t0, t1, t2) if j else (t0, t2, t1))

    return triangles