Weird boolean conversion (?)

Question

Explain pleasy why second expression returns false

   cout << (4==4) << endl; //1
   cout << (4==4==4) << endl; // 0

Answer 1

(4==4==4) is basically ((4==4)==4) which is (true == 4) which is (1==4) ¹ which is false ² which is getting printed as 0.

Note that == has associativity left-to-right, but that doesn't matter (in this case) because even if it had associativity right-to-left, the result would have been the same.

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<sup>1. Due to integral promotion.
2. Note that one might tempted to think 4 in (true==4) could be treated as true (after all 4 is non-zero, hence true). This thinking might conclude (true==4) is (true==true) which is true. But that is not how it works. It is the bool which gets promoted to int, instead of int to bool.</sup>