primes.H

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/*
                          Aleph_w
 
  Data structures & Algorithms
  version 2.0.0b
  https://github.com/lrleon/Aleph-w
 
  This file is part of Aleph-w library
 
  Copyright (c) 2002-2026 Leandro Rabindranath Leon
 
  Permission is hereby granted, free of charge, to any person obtaining a copy
  of this software and associated documentation files (the "Software"), to deal
  in the Software without restriction, including without limitation the rights
  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  copies of the Software, and to permit persons to whom the Software is
  furnished to do so, subject to the following conditions:
 
  The above copyright notice and this permission notice shall be included in all
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  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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*/
 
 
# ifndef PRIMES_H
# define PRIMES_H
 
# include <cmath>
# include <ahDefs.H>
# include <ah-errors.H>
 
namespace Primes
{
 
  extern const unsigned long DefaultPrime;
 
  extern const size_t numPrimes;
 
  extern const unsigned long primeList[];
 
  extern unsigned long next_prime(unsigned long n);
 
  extern bool check_primes_database();
 
  inline bool is_prime(unsigned long n)
  {
    if (n <= 1) 
      return false;
    
    for (int i = 2; i <= sqrt(n); i++) 
      if (n % i == 0) 
        return false;
    
    return true;
  }
 
  inline unsigned long next_prime_number_greater_than(unsigned long n)
  {
    if (n <= 1)
      return 2;
 
    if (n == 2)
      return 3;
 
    const unsigned long max = std::numeric_limits<unsigned long>::max();
 
    ah_domain_error_if(n == max)
      << "next_prime_number_greater_than: overflow error";
 
    // if n is even, add 1
    if (n % 2 == 0)
      ++n;
 
    ah_domain_error_if(n == max)
      << "next_prime_number_greater_than: overflow error";
 
    unsigned long p = n + 2;
    while (not is_prime(p))
      {
        ah_domain_error_if(p + 1 == max or p + 2 == max)
          << "next_prime_number_greater_than: overflow error";
        p += 2;
      }
 
    return p;
  }
  
}; /* namespace Primes */
 
# endif /* PRIMES_H */