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I was trying to multiply two integers using recursion, and wrote this code, accidently: //the original version int multiply(int a, int b) { if ( !b ) return 0; else return a + multiply(a, b ? --b : ++b ); //accident } I said, I wrote this accidently, because I intended to write : b > 0 ? --b : ++b instead of b ? --b : ++b I realize that what I intended to write wouldn't work . But what is surprising to me is, what I did not intend to write does work . Now, I note that b ?--b : ++b is basically equivalent to --b because b in else-block is guaranteed to be non-zero. So I modified the above code, replacing b?--b:++b with --b , as shown below: //the modified version int multiply(int a, int b) { if ( !b ) return 0; else return a + multiply(a, --b); //modification here } Since the original version woks, I expected the modified version to work as well. But again, to my surprise, it doesn't work! What is wrong the modified version? Is it not equivalent to the original version? Is --b not equivalent to b ?--b : ++b IF b is non-zero? If its equivalent, then why does the first code work but the second doesn't? Note: here, by "work", I mean it gives the correct output. That is, it gives the multiplication of the integers passed to the function.

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