Operator Precedence in C++/Java

Question

I have been diving deep into understanding the operator precedence in Object oriented programming. Given below is the code:

             int a=5;
             int b=5;
             printf("Output %d",a++>b);
             return 0;

The output is Output 0.

As per my understanding, unary operators has higher precedence over relational operator. So shouldn't a++>b be 6>5. Which is True. But the code outputs False. can anybody explain me why?

Thank you in advance.

The postfix `a++` returns `5` - The prefix `++a` would return `6` — Ted Lyngmo, Mar 11 '21 at 18:51
related/dupe: https://stackoverflow.com/questions/7031326/what-is-the-difference-between-prefix-and-postfix-operators — NathanOliver, Mar 11 '21 at 18:52
also: https://stackoverflow.com/questions/5413548/java-prefix-postfix-of-increment-decrement-operators — NathanOliver, Mar 11 '21 at 18:52
look similar to the ["goes to operator"](https://stackoverflow.com/questions/1642028/what-is-the-operator-in-c-c) — 463035818_is_not_an_ai, Mar 11 '21 at 18:52
This isn't related to operator precedence at all because there's nothing to disambiguate. The only way to interpret this code is that `++` applies to `a` and `>` applies to `a++` and `b`. — chris, Mar 11 '21 at 18:57

score 2 · Answer 1 · answered Mar 11 '21 at 19:06

You get false because you're using the postfix increment operator when you're doing a++, which in your case results in the comparison 5 > 5.

The postfix increment operator can be thought of in this way. Note: It's illegal code made to demonstrate this only:

class int {                 // if there had been an "int" class
    int operator++(int) {   // postfix increment 
        int copy = *this;   // make a copy of the current value
        *this = *this + 1;  // add one to the int object
        return copy;        // return the OLD value
    }
};

If you had used the prefix increment operator, ++a, you'd gotten the comparison 6 > 5 - and therefor the result true. The prefix increment operator can be thought of in this way. Again, illegal code:

class int {
    int& operator++() {    // prefix increment
        *this = *this + 1; // add one to the int object
        return *this;      // return a reference to the actual object
    }
};

Operator Precedence in C++/Java

1 Answers1