What's the difference between these blocks of code? (with ++i increment)

Question

// example 1
int a = 3;
int b = ++a; // a is now 4, thus b is 4
int c = ++a; // a is now 5, thus c is 5
int d = b + c; // 4 + 5
cout << d << endl; // the result is 9

// example 2
int e = 3;
int f = (++e) + (++e); // ???
cout << f; // result is 10 (profit?)

As I understand it, ++i means increment the value of i then returns the incremented value, as opposed to i++ which returns the value before operation. Explanation?

Answer 1

Code Playground:
http://www.sololearn.com/app/sololearn/playground/c7BLm0LMpnvi/

Answer 2

That is because of the Operator Precedence in C++. It executes the postfix and prefix operation always before the addition/subtraction operation.

http://en.cppreference.com/w/cpp/language/operator_precedence

Answer 3

Hi. I understand that the postfix and prefix is executed before the addition, but where does the extra 1 coming from? Since they were executed before the addition, wouldn't that leaves 4 and 5 to be added? Care for step by step explanation on what happened during f = (++e) + (++e)?