Source code for httk.io.cif.symops_utils

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def compose_ops_with_centerings(ops, centerings):
    """
    Compose symmetry operations with centering translations.

    ``ops`` is a list of ``(R, t, time_flag)`` operations and ``centerings`` is a list
    of ``(c, time_c)`` where ``c`` is a 3-vector fractional translation and ``time_c``
    is 0 or 1 (0 means no time reversal). Returns a new list of ``(R, t', time')`` where
    ``t' = t + c`` and ``time' = (time_flag + time_c) % 2``.
    """
    composed = []
    for R, t, time_flag in ops:
        for Rc, c, time_c in centerings:
            if Rc != ((1, 0, 0), (0, 1, 0), (0, 0, 1)):
                raise Exception("Centering symop that includes rotation is invalid")
            t_new = (t[0] + c[0], t[1] + c[1], t[2] + c[2])
            time_new = (time_flag + time_c) % 2  # time_flag * time_c for -1/+1 convention
            composed.append((R, t_new, time_new))
    return composed