void
expression_plus_compile::generate_code() {
    lhs->generate_code();
    rhs->generate_code();
    switch (PAIR(lhs->get_type(), rhs->get_type()))
    {
    case PAIR(TYPE_INTEGER, TYPE_INTEGER):
        emit(OP_ADI);
        break;

    case PAIR(TYPE_REAL, TYPE_INTEGER):
        emit(OP_FLT);
        emit(OP_ADR);
        break;

    case PAIR(TYPE_INTEGER, TYPE_REAL):
        emit(OP_FLO);
        emit(OP_ADR);
        break;

    case PAIR(TYPE_REAL, TYPE_REAL):
        emit(OP_ADR);
        break;
    } } 

 void
expression_plus_integer_compile::generate_code() {
    lhs->generate_code();
    rhs->generate_code();
    emit(OP_ADI); }

// and take care of the implict casts // somewhere
else, too.

void expression_plus_real_compile::generate_code() {
    lhs->generate_code();
    rhs->generate_code();
    emit(OP_ADR); }