permlib  0.2.6
Library for permutation computations
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include/permlib/prime_helper.h
00001 // ---------------------------------------------------------------------------
00002 //
00003 //  This file is part of PermLib.
00004 //
00005 // Copyright (c) 2009-2011 Thomas Rehn <thomas@carmen76.de>
00006 // All rights reserved.
00007 // 
00008 // Redistribution and use in source and binary forms, with or without
00009 // modification, are permitted provided that the following conditions
00010 // are met:
00011 // 1. Redistributions of source code must retain the above copyright
00012 //    notice, this list of conditions and the following disclaimer.
00013 // 2. Redistributions in binary form must reproduce the above copyright
00014 //    notice, this list of conditions and the following disclaimer in the
00015 //    documentation and/or other materials provided with the distribution.
00016 // 3. The name of the author may not be used to endorse or promote products
00017 //    derived from this software without specific prior written permission.
00018 // 
00019 // THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
00020 // IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
00021 // OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
00022 // IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
00023 // INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
00024 // NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
00025 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
00026 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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00028 // THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
00029 //
00030 // ---------------------------------------------------------------------------
00031 
00032 #ifndef PRIME_HELPER_H_
00033 #define PRIME_HELPER_H_
00034 
00035 #include <algorithm>
00036 #include <boost/assert.hpp>
00037 
00038 namespace permlib {
00039 
00041 class PrimeHelper {
00042 public:
00044         static const unsigned int largestNumberForPrimalityCheck;
00045 
00047 
00052         static bool isPrimeNumber(unsigned int x, bool checkBounds) {
00053                 if (checkBounds && x > largestNumberForPrimalityCheck) {
00054                         // number too big for our simple check
00055                         BOOST_ASSERT( false );
00056                         return false;
00057                 }
00058                 
00059                 if (x > largestNumberForPrimalityCheck) {
00060                         // the number is to big for our simple check
00061                         return false;
00062                 } else if (x > largestPrime) {
00063                         for (unsigned int i = 0; i < numberOfPrimes; ++i) {
00064                                 if ((x % primes[i]) == 0)
00065                                         return false;
00066                         }
00067                         return true;
00068                 }
00069                 return std::binary_search(primes, primes+numberOfPrimes, x);
00070         }
00071         
00073         static const unsigned int* firstPrime() { return primes; }
00075         static const unsigned int* lastPrime() { return primes + numberOfPrimes; }
00076 private:
00077         static const unsigned int numberOfPrimes;
00078         // This list is probably incomplete ;)
00079         static const unsigned int primes[];
00080         static const unsigned int largestPrime;
00081 };
00082 
00083 const unsigned int PrimeHelper::numberOfPrimes = 170;
00084 // Probably this list is incomplete ;)
00085 const unsigned int PrimeHelper::primes[numberOfPrimes] = { 
00086         2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97,101,103,107,109,113,
00087         127,131,137,139,149,151,157,163,167,173,179,181,191,193,197,199,211,223,227,229,233,239,241,251,257,263,269,271,277,281, 
00088         283,293,307,311,313,317,331,337,347,349,353,359,367,373,379,383,389,397,401,409,419,421,431,433,439,443,449,457,461,463,
00089         467,479,487,491,499,503,509,521,523,541,547,557,563,569,571,577,587,593,599,601,607,613,617,619,631,641,643,647,653,659,
00090         661,673,677,683,691,701,709,719,727,733,739,743,751,757,761,769,773,787,797,809,811,821,823,827,829,839,853,857,859,863,
00091         877,881,883,887,907,911,919,929,937,941,947,953,967,971,977,983,991,997,1009,1013
00092 };
00093 const unsigned int PrimeHelper::largestPrime = primes[numberOfPrimes-1];
00094 const unsigned int PrimeHelper::largestNumberForPrimalityCheck = largestPrime * largestPrime;
00095 
00096 }
00097 
00098 #endif