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copied!<p>Taking advantage of short-circuiting in boolean expressions:</p> <pre><code>int max(int a, int b, int c) { int m = a; (m < b) && (m = b); //these are not conditional statements. (m < c) && (m = c); //these are just boolean expressions. return m; } </code></pre> <p><strong>Explanation:</strong> </p> <p>In boolean <code>AND</code> operation such as <code>x && y</code>, y is evaluated <strong>if and only if</strong> <code>x</code> is true. If <code>x</code> is false, then <code>y</code> is not evaluated, because the whole expression would be false which can be deduced without even evaluating <code>y</code>. This is called short-circuiting when the value of a boolean expression can be deduced without evaluating all operands in it.</p> <p>Apply this principle to the above code. Initially <code>m</code> is <code>a</code>. Now if <code>(m < b)</code> is true, then that means, <code>b</code> is greater than <code>m</code> (which is actually <code>a</code>), so the second subexpression <code>(m = b)</code> is evaluated and <code>m</code> is set to <code>b</code>. If however <code>(m < b)</code> is false, then second subexpression will not be evaluated and <code>m</code> will remain <code>a</code> (which is greater than <code>b</code>). In a similar way, second expression is evaluated (on the next line).</p> <p>In short, you can read the expression <code>(m < x) && (m = x)</code> as follows : set <code>m</code> to <code>x</code> <strong>if and only if</strong> <code>m</code> is less than <code>x</code> i.e <code>(m < x)</code> is true. Hope this helps you understanding the code.</p> <p><strong>Test code:</strong> </p> <pre><code>int main() { printf("%d\n", max(1,2,3)); printf("%d\n", max(2,3,1)); printf("%d\n", max(3,1,2)); return 0; } </code></pre> <p><strong>Output:</strong></p> <pre><code>3 3 3 </code></pre> <p><strong>Online Demo:</strong> <a href="http://www.ideone.com/8045P" rel="noreferrer">http://www.ideone.com/8045P</a></p> <p>Note the implementation of <code>max</code> gives warnings because evaluated expressions are not used:</p> <blockquote> <p>prog.c:6: warning: value computed is not used<br> prog.c:7: warning: value computed is not used</p> </blockquote> <p>To avoid these (harmless) warnings, you can implement <code>max</code> as:</p> <pre><code>int max(int a, int b, int c) { int m = a; (void)((m < b) && (m = b)); //these are not conditional statements. (void)((m < c) && (m = c)); //these are just boolean expressions. return m; } </code></pre> <p>The trick is that now we're <a href="https://stackoverflow.com/questions/689677/casting-unused-return-values-to-void/7160837#7160837">casting the boolean expressions to <code>void</code>, which causes suppression of the warnings</a>: </p> <ul> <li><a href="http://www.ideone.com/PZ1sP" rel="noreferrer">http://www.ideone.com/PZ1sP</a></li> </ul>

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