c++ reference parameter not updated

Question

I'm trying to write a simple function to extract the next number from an expression in a string and my problem is that the reference parameter ioIsValidExpression is not being updated after the function exits. It looks like I am actually referencing the correct variable (and not a temporary) since the addresses of test3 (as it is called before calling getNextNumber(...)) and ioIsValidExpression (its name when inside the function) are the same. I expect this to be an embarassing mistake somewhere but I'm getting nowhere trying to figure this one out; I've included my int main and int getNextNumber with a comment line where I return a value from the function. ``` int getNextNumber(std::string& iExpression, int& ioLoopShift, bool& ioIsValidExpression) { //spaces are ignored, a minus is a unary minus (so must be seated next to a number (no spaces between '-' and number)) int length = iExpression.size(); //evaluate only once bool unaryMinusFound = false; bool numberFound = false; int oSubE…

Accepted Answer

The order in which function arguments (and your output statement is a chain of functions) are evaluated is unspecified. Consider how it works correctly upon holding the result of the function in a variable before outputting the whole thing: test

```
int temp = getNextNumber(test, test2, test3);
std::cout << temp << ", address of test3: " << &test3 << ", value: " << test3 << "
";
```

Output:

address of ioIsValidExpression: 0xbfaa85cf, value: 0 0, address of test3: 0xbfaa85cf, value: 0

c++ reference parameter not updated

Solution

Problem