def dihed_iter(self, g_nums, ats_1, ats_2, ats_3, ats_4, \
                                                    invalid_error=False):
        from .utils import pack_tups
        if _DEBUG:
            print("g_nums = {0}".format(g_nums))
            print("ats_1 = {0}".format(ats_1))
            print("ats_2 = {0}".format(ats_2))
            print("ats_3 = {0}".format(ats_3))
            print("ats_4 = {0}".format(ats_4))
        arglist = self._none_subst(g_nums, ats_1, ats_2, ats_3, ats_4)
        tups = pack_tups(*arglist)
        if _DEBUG:
            print(tups)
        for tup in tups:
            yield self._iter_return(tup, self.dihed_single, invalid_error)