permlib  0.2.9
Library for permutation computations
prime_helper.h
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31 
32 #ifndef PRIME_HELPER_H_
33 #define PRIME_HELPER_H_
34 
35 #include <algorithm>
36 #include <boost/assert.hpp>
37 
38 namespace permlib {
39 
41 class PrimeHelper {
42 public:
44  static const unsigned int largestNumberForPrimalityCheck;
45 
47 
52  static bool isPrimeNumber(unsigned int x, bool checkBounds) {
53  if (checkBounds && x > largestNumberForPrimalityCheck) {
54  // number too big for our simple check
55  BOOST_ASSERT( false );
56  return false;
57  }
58 
60  // the number is to big for our simple check
61  return false;
62  } else if (x > largestPrime) {
63  for (unsigned int i = 0; i < numberOfPrimes; ++i) {
64  if ((x % primes[i]) == 0)
65  return false;
66  }
67  return true;
68  }
69  return std::binary_search(primes, primes+numberOfPrimes, x);
70  }
71 
73  static const unsigned int* firstPrime() { return primes; }
75  static const unsigned int* lastPrime() { return primes + numberOfPrimes; }
76 private:
77  static const unsigned int numberOfPrimes;
78  // This list is probably incomplete ;)
79  static const unsigned int primes[];
80  static const unsigned int largestPrime;
81 };
82 
83 #define PRIME_HELPER_NUMBER_OF_PRIMES 170
84 const unsigned int PrimeHelper::numberOfPrimes = PRIME_HELPER_NUMBER_OF_PRIMES;
85 // Probably this list is incomplete ;)
86 const unsigned int PrimeHelper::primes[PRIME_HELPER_NUMBER_OF_PRIMES] = {
87  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,
88  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,
89  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,
90  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,
91  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,
92  877,881,883,887,907,911,919,929,937,941,947,953,967,971,977,983,991,997,1009,1013
93 };
94 const unsigned int PrimeHelper::largestPrime = primes[numberOfPrimes-1];
95 const unsigned int PrimeHelper::largestNumberForPrimalityCheck = largestPrime * largestPrime;
96 
97 }
98 
99 #endif
static const unsigned int largestNumberForPrimalityCheck
The number up to which this simple primality check is always correct.
Definition: prime_helper.h:44
helper class for primality checks
Definition: prime_helper.h:41
static const unsigned int * lastPrime()
iterator pointing after the last prime in list
Definition: prime_helper.h:75
static const unsigned int * firstPrime()
iterator pointing to the first prime in list
Definition: prime_helper.h:73
static bool isPrimeNumber(unsigned int x, bool checkBounds)
checks if a given number is prime
Definition: prime_helper.h:52
Definition: abstract_bsgs.h:49