Comments on: A C++ quote and a C trivia question http://www.dubovsky.com/rantings/2006/07/09/a-c-quote-and-a-c-trivia-question/ Yet another web log of personal junk. Tue, 06 Jan 2009 13:59:31 +0000 http://wordpress.org/?v=2.6.3 By: jon http://www.dubovsky.com/rantings/2006/07/09/a-c-quote-and-a-c-trivia-question/#comment-54 jon Sun, 09 Jul 2006 17:47:03 +0000 http://www.dubovsky.com/rantings/2006/07/09/a-c-quote-and-a-c-trivia-question/#comment-54 The short answer: the programmer was trying to do a C++-ish thing (use a boolean-value variable) but botched it: <code>int</code> is not <code>bool</code>. The long answer. The <code>&=</code> operation is a <em>bitwise</em> or, not a <em>logical</em> (boolean) one. If the function returned the value 2 (or any even value), bool would be set to <code>2 & 1</code>, which is 0, erroneously indicating an error when there was none. I believe the original programmer was thinking of <code>2 && 1</code>, which would of course work correctly. Alas, there is no <code>&&=</code> operator in C or C++. The short answer: the programmer was trying to do a C++-ish thing (use a boolean-value variable) but botched it: int is not bool.

The long answer. The &= operation is a bitwise or, not a logical (boolean) one. If the function returned the value 2 (or any even value), bool would be set to 2 & 1, which is 0, erroneously indicating an error when there was none. I believe the original programmer was thinking of 2 && 1, which would of course work correctly. Alas, there is no &&= operator in C or C++.

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