int CompoundExp::eval(EvalState & state) {
if (op == "=") {
if (lhs->getType() != IDENTIFIER) {
error("Illegal variable in assignment");
}
int val = rhs->eval(state);
state.setValue(((IdentifierExp *) lhs)->getName(), val);
return val;
}
int left = lhs->eval(state);
int right = rhs->eval(state);
if (op == "+") return left + right;
if (op == "-") return left - right;
if (op == "*") return left * right;
if (op == "/") {
if (right == 0) {
cout << "DIVIDE BY ZERO" << endl;
error("");
}
else {
return left / right;
}
}
return 0;
}
void LetStmt::execute(EvalState & state) {
state.setValue(identifier, exp->eval(state));
}
void InputStmt::execute(EvalState & state) {
int value = getInteger("? ");
state.setValue(identifier, value);
}
void LetStmt::execute(EvalState &state) {
int value = exp->eval(state);
state.setValue(identifier, value);
}