What's going under the hood in this simple C++ code?

Question

#include<iostream>
int main()
{ 
    int a = 5;
    a = (a = 10, a++, a--);
    std::cout << a;

}

Output is 11, But when I modify the line

a = a=10,a++,a--;

Output is 10 What effect does removing the ( ) operator has and in what order the operators are being executed.

Comma has [lowest precedence](http://stackoverflow.com/a/18444099/1708801) — Shafik Yaghmour, Jul 29 '15 at 18:42
Wait, what? undefined behavior? The comma operator introduces a sequence point @πάνταῥεῖ — Shafik Yaghmour, Jul 29 '15 at 18:44
_What effect does removing the ( ) operator has and in what order the operators are being executed_ Better question: why are you so uninterested in learning these details that you would rather ask random people for help? Write some code and figure the answer out yourself. For self-bonus points, inspect the assembly code the compiler can generate (if you ask it to) and spend some time to understand it. — mah, Jul 29 '15 at 18:44

score 0 · Answer 1 · answered Jul 29 '15 at 18:42

The + and - operators take precedence before the assignment operator and the +,- signs are read by the compiler from left to right, whereas the assignment operators are read by the compiler from right to left. So: 1) a++ 2) a-- 3) a=10 4) a =

score 0 · Answer 2 · answered Jan 22 '16 at 17:06

0

The c++ compiler will pass your complete set code to a binary tree which will rearrange your code according to the precedence of the operator = + - etc in left node or right node

answered Jan 22 '16 at 17:06

Amnoid Lab

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What's going under the hood in this simple C++ code?

2 Answers2