def _idices2slices(a, a0=0, a1=99):
    """Converts an iterable of split-point indices into an array of range indices.

    E.g.,
        []      --> [(a0,a1)]
        [4]     --> [(a0, 3), (4, a1)]
        [2,3,6] --> [(a0, 1), (2, 2), (3, 5), (6, a1)]
    """

    if a is None or len(a) == 0:
        return [(a0,a1)]
    return [(a[i-1] if i > 0 else a0, a[i]-1) for i in range(len(a))] + [(a[-1], a1)]