MPE_OP_TAIL_NOOP,   ///< resume at most once without performing operations; and if resumed, it is the last action performed by the operation function.
MPE_OP_TAIL,        ///< resume at most once; and if resumed, it is the last action performed by the operation function.

MPE_DEFINE_EFFECT1(sphinx, answer)
MPE_DEFINE_VOIDOP1(sphinx, answer, mpe_string_t)

void* brian(void* arg){
    UNUSED(arg);
    // Arrive at Thebes
    sphinx_answer("Scooters");
    // Die
    mpt_assert(false, "Brian should have been eaten by the sphinx");
    return mpe_voidp_int(1);
}

/*-----------------------------------------------------------------
  Sphinx handler
-----------------------------------------------------------------*/

static void* _sphinx_answer(mpe_resume_t* r, void* local, void* arg){
    if (strcmp(mpe_mpe_string_t_voidp(arg), "Person") == 0) {
        return mpe_resume_tail(r, local, NULL);
    } else {
        // I couldn't find a way to release it, this one is not intended for MPE_RESUMPTION_INPLACE
        // mpe_resume_release(r);
        return mpe_voidp_int(0);
    }
}

static const mpe_handlerdef_t sphinx_hdef = { MPE_EFFECT(sphinx), NULL, {
    { MPE_OP_TAIL, MPE_OPTAG(sphinx, answer), &_sphinx_answer },
    { MPE_OP_NULL, mpe_op_null, NULL}
}};

static void* sphinx_handle(mpe_actionfun_t action) {
    return mpe_handle(&sphinx_hdef, NULL, action, NULL);
}