Why does logical OR operator not evaluating the parenthesized right hand side condition first?

Question

Consider the code:

int i=2, j=3;
if(i<5 or (++i==j))
    cout << "i=" << i;

The output is:

i=2

Why not using parenthesis have any effect in the above condition? Why not the output is 3?

compiler: g++ 4.8.2 on Ubuntu 14.04LTS

Answer 1

or is the same as || , which performs a short-circuit evaluation from left to right. This means that once the result of the expression containing || is known, evaluation stops.

( || is also a sequencing point, so the behaviour is well-defined even in the case where i >= 5 ).

Since i < 5 is true , the other expression is not computed; so i is not incremented.