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The following code gives a weird output. I have tried it on multiple compilers and ended up with the same answer. It will process the statement right to left but print the output left to right however c++ statements are evaulated left to right in general. Can someone explain why this happens when we overload the cout statement.

Output: 15 10 5

However the Output if processed from left to right should be: 8 10 12

#include<iostream>
using namespace std;

int main(){
    int a = 5, b = 3, c = 2;
    cout<< (a = b + a) << endl << (b = c + a) << endl << (c = b  + c);
    return 0;
}
Talha Zubair
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  • I agree on the unspecified behavior but it relates to sequence points altogether. If you can find a better one be my guest, otherwise we might reopen it. – Marco A. Sep 30 '15 at 14:26
  • Here is a near duplicate: http://stackoverflow.com/questions/2603312/the-result-of-int-c-0-coutcc – Paul R Sep 30 '15 at 14:29
  • Thanks for the answers everyone. Sorry im new here so i tried searching according to my limited knowledge but didnt find any suitable question. – Talha Zubair Sep 30 '15 at 14:32

1 Answers1

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This will result in unspecified behavior. The order in which the operations execute isn't specified (since there are no sequence points between them), so the three assignments

a = b + a
b = c + a
c = b + c

can occur in any order. Therefore the output from cout is also unspecified .

Cory Kramer
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