string const& lhs = s.get_lhs();
    vexp::varexpression_ptr rhs = s.get_rhs();
    cexp::counterexp_ptr null_cc;
    int s_id = s.get_id();

    env->forall_vals([&] (vexp::Environment& e) {
        string cur_control = make_control(e);
        string cur_stack   = make_stack(s_id, e);

        e.set_value(lhs, rhs->evaluate(e));

        string next_control = make_control(e);
        string next_stack   = make_stack(cont, e);

        add_rewrite(cur_control, cur_stack, E_ACT, next_control, next_stack, null_cc);
    });