michael@0: // Copyright 2005, Google Inc.
michael@0: // All rights reserved.
michael@0: //
michael@0: // Redistribution and use in source and binary forms, with or without
michael@0: // modification, are permitted provided that the following conditions are
michael@0: // met:
michael@0: //
michael@0: //     * Redistributions of source code must retain the above copyright
michael@0: // notice, this list of conditions and the following disclaimer.
michael@0: //     * Redistributions in binary form must reproduce the above
michael@0: // copyright notice, this list of conditions and the following disclaimer
michael@0: // in the documentation and/or other materials provided with the
michael@0: // distribution.
michael@0: //     * Neither the name of Google Inc. nor the names of its
michael@0: // contributors may be used to endorse or promote products derived from
michael@0: // this software without specific prior written permission.
michael@0: //
michael@0: // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
michael@0: // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
michael@0: // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
michael@0: // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
michael@0: // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
michael@0: // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
michael@0: // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
michael@0: // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
michael@0: // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
michael@0: // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
michael@0: // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
michael@0: 
michael@0: // A sample program demonstrating using Google C++ testing framework.
michael@0: //
michael@0: // Author: wan@google.com (Zhanyong Wan)
michael@0: 
michael@0: #include "sample1.h"
michael@0: 
michael@0: // Returns n! (the factorial of n).  For negative n, n! is defined to be 1.
michael@0: int Factorial(int n) {
michael@0:   int result = 1;
michael@0:   for (int i = 1; i <= n; i++) {
michael@0:     result *= i;
michael@0:   }
michael@0: 
michael@0:   return result;
michael@0: }
michael@0: 
michael@0: // Returns true iff n is a prime number.
michael@0: bool IsPrime(int n) {
michael@0:   // Trivial case 1: small numbers
michael@0:   if (n <= 1) return false;
michael@0: 
michael@0:   // Trivial case 2: even numbers
michael@0:   if (n % 2 == 0) return n == 2;
michael@0: 
michael@0:   // Now, we have that n is odd and n >= 3.
michael@0: 
michael@0:   // Try to divide n by every odd number i, starting from 3
michael@0:   for (int i = 3; ; i += 2) {
michael@0:     // We only have to try i up to the squre root of n
michael@0:     if (i > n/i) break;
michael@0: 
michael@0:     // Now, we have i <= n/i < n.
michael@0:     // If n is divisible by i, n is not prime.
michael@0:     if (n % i == 0) return false;
michael@0:   }
michael@0: 
michael@0:   // n has no integer factor in the range (1, n), and thus is prime.
michael@0:   return true;
michael@0: }