In C++, the output starts from right or left ?

Question

Int a=0;
Cout<<a++<<++a<<a<<a++;

//Output: 0222 or Output: 2210 ??

Answer 1

Very interesting UB ¹!

The compilation log:

"warning: operation on 'a' may be undefined [-Wsequence-point]"

Reason:

"When modifying an object between two sequence points, reading the value of the object for any other purpose than determining the value to be stored is also undefined behavior."

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¹ https://en.wikipedia.org/wiki/Undefined_behavior#Examples_in_C_and_C++

Answer 2

Felix Moelder, C++ Soldier (Babak) - Thanks for the information. 🙂

Answer 3

From left to right