def parse_definite_clause(s):
    "Return the antecedents and the consequent of a definite clause."
    assert is_definite_clause(s)
    if is_symbol(s.op):
        return [], s
    else:
        antecedent, consequent = s.args
        return conjuncts(antecedent), consequent
Return the antecedents and the consequent of a definite clause.