text: /* boost random/linear_congruential.hpp header file
   *
   * Copyright Jens Maurer 2000-2001
   * Distributed under the Boost Software License, Version 1.0. (See
   * accompanying file LICENSE_1_0.txt or copy at
   * http://www.boost.org/LICENSE_1_0.txt)
   *
   * See http://www.boost.org for most recent version including documentation.
   *
   * $Id: linear_congruential.hpp,v 1.22 2005/05/21 15:57:00 dgregor Exp $
   *
   * Revision history
   *  2001-02-18  moved to individual header files
   */
  
  #ifndef BOOST_RANDOM_LINEAR_CONGRUENTIAL_HPP
  #define BOOST_RANDOM_LINEAR_CONGRUENTIAL_HPP
  
  #include <iostream>
  #include <cassert>
  #include <stdexcept>
  #include <boost/config.hpp>
  #include <boost/limits.hpp>
  #include <boost/static_assert.hpp>
  #include <boost/random/detail/const_mod.hpp>
  #include <boost/detail/workaround.hpp>
  
  namespace boost {
  namespace random {
  
  // compile-time configurable linear congruential generator
  template<class IntType, IntType a, IntType c, IntType m, IntType val>
  class linear_congruential
  {
  public:
    typedef IntType result_type;
  #ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION
    static const bool has_fixed_range = true;
    static const result_type min_value = ( c == 0 ? 1 : 0 );
    static const result_type max_value = m-1;
  #else
    BOOST_STATIC_CONSTANT(bool, has_fixed_range = false);
  #endif
    BOOST_STATIC_CONSTANT(IntType, multiplier = a);
    BOOST_STATIC_CONSTANT(IntType, increment = c);
    BOOST_STATIC_CONSTANT(IntType, modulus = m);
  
    // MSVC 6 and possibly others crash when encountering complicated integral
    // constant expressions.  Avoid the check for now.
    // BOOST_STATIC_ASSERT(m == 0 || a < m);
    // BOOST_STATIC_ASSERT(m == 0 || c < m);
  
    explicit linear_congruential(IntType x0 = 1)
      : _modulus(modulus), _x(_modulus ? (x0 % _modulus) : x0)
    { 
      assert(c || x0); /* if c == 0 and x(0) == 0 then x(n) = 0 for all n */
      // overflow check
      // disabled because it gives spurious "divide by zero" gcc warnings
      // assert(m == 0 || (a*(m-1)+c) % m == (c < a ? c-a+m : c-a)); 
  
      // MSVC fails BOOST_STATIC_ASSERT with std::numeric_limits at class scope
  #ifndef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS
      BOOST_STATIC_ASSERT(std::numeric_limits<IntType>::is_integer);
  #endif
    }
  
    template<class It>
    linear_congruential(It& first, It last) { seed(first, last); }
  
    // compiler-generated copy constructor and assignment operator are fine
    void seed(IntType x0 = 1)
    {
      assert(c || x0);
      _x = (_modulus ? (x0 % _modulus) : x0);
    }
  
    template<class It>
    void seed(It& first, It last)
    {
      if(first == last)
        throw std::invalid_argument("linear_congruential::seed");
      IntType value = *first++;
      _x = (_modulus ? (value % _modulus) : value);
    }
  
    result_type min BOOST_PREVENT_MACRO_SUBSTITUTION () const { return c == 0 ? 1 : 0; }
    result_type max BOOST_PREVENT_MACRO_SUBSTITUTION () const { return modulus-1; }
  
    IntType operator()()
    {
      _x = const_mod<IntType, m>::mult_add(a, _x, c);
      return _x;
    }
  
    static bool validation(IntType x) { return val == x; }
  
  #ifdef BOOST_NO_OPERATORS_IN_NAMESPACE
      
    // Use a member function; Streamable concept not supported.
    bool operator==(const linear_congruential& rhs) const
    { return _x == rhs._x; }
    bool operator!=(const linear_congruential& rhs) const
    { return !(*this == rhs); }
  
  #else 
    friend bool operator==(const linear_congruential& x,
                           const linear_congruential& y)
    { return x._x == y._x; }
    friend bool operator!=(const linear_congruential& x,
                           const linear_congruential& y)
    { return !(x == y); }
      
  #if !defined(BOOST_NO_MEMBER_TEMPLATE_FRIENDS) && !BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x551))
    template<class CharT, class Traits>
    friend std::basic_ostream<CharT,Traits>&
    operator<<(std::basic_ostream<CharT,Traits>& os,
               const linear_congruential& lcg)
    {
      return os << lcg._x;
    }
  
    template<class CharT, class Traits>
    friend std::basic_istream<CharT,Traits>&
    operator>>(std::basic_istream<CharT,Traits>& is,
               linear_congruential& lcg)
    {
      return is >> lcg._x;
    }
   
  private:
  #endif
  #endif
      
    IntType _modulus;   // work-around for gcc "divide by zero" warning in ctor
    IntType _x;
  };
  
  // probably needs the "no native streams" caveat for STLPort
  #if !defined(__SGI_STL_PORT) && BOOST_WORKAROUND(__GNUC__, == 2)
  template<class IntType, IntType a, IntType c, IntType m, IntType val>
  std::ostream&
  operator<<(std::ostream& os,
             const linear_congruential<IntType,a,c,m,val>& lcg)
  {
      return os << lcg._x;
  }
  
  template<class IntType, IntType a, IntType c, IntType m, IntType val>
  std::istream&
  operator>>(std::istream& is,
             linear_congruential<IntType,a,c,m,val>& lcg)
  {
      return is >> lcg._x;
  }
  #elif defined(BOOST_NO_OPERATORS_IN_NAMESPACE) || defined(BOOST_NO_MEMBER_TEMPLATE_FRIENDS) || BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x551))
  template<class CharT, class Traits, class IntType, IntType a, IntType c, IntType m, IntType val>
  std::basic_ostream<CharT,Traits>&
  operator<<(std::basic_ostream<CharT,Traits>& os,
             const linear_congruential<IntType,a,c,m,val>& lcg)
  {
      return os << lcg._x;
  }
  
  template<class CharT, class Traits, class IntType, IntType a, IntType c, IntType m, IntType val>
  std::basic_istream<CharT,Traits>&
  operator>>(std::basic_istream<CharT,Traits>& is,
             linear_congruential<IntType,a,c,m,val>& lcg)
  {
      return is >> lcg._x;
  }
  #endif
  
  #ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION
  //  A definition is required even for integral static constants
  template<class IntType, IntType a, IntType c, IntType m, IntType val>
  const bool linear_congruential<IntType, a, c, m, val>::has_fixed_range;
  template<class IntType, IntType a, IntType c, IntType m, IntType val>
  const typename linear_congruential<IntType, a, c, m, val>::result_type linear_congruential<IntType, a, c, m, val>::min_value;
  template<class IntType, IntType a, IntType c, IntType m, IntType val>
  const typename linear_congruential<IntType, a, c, m, val>::result_type linear_congruential<IntType, a, c, m, val>::max_value;
  template<class IntType, IntType a, IntType c, IntType m, IntType val>
  const IntType linear_congruential<IntType,a,c,m,val>::modulus;
  #endif
  
  } // namespace random
  
  // validation values from the publications
  typedef random::linear_congruential<int32_t, 16807, 0, 2147483647, 
    1043618065> minstd_rand0;
  typedef random::linear_congruential<int32_t, 48271, 0, 2147483647,
    399268537> minstd_rand;
  
  
  #if !defined(BOOST_NO_INT64_T) && !defined(BOOST_NO_INTEGRAL_INT64_T)
  // emulate the lrand48() C library function; requires support for uint64_t
  class rand48 
  {
  public:
    typedef int32_t result_type;
  #ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION
    static const bool has_fixed_range = true;
    static const int32_t min_value = 0;
    static const int32_t max_value = integer_traits<int32_t>::const_max;
  #else
    enum { has_fixed_range = false };
  #endif
    int32_t min BOOST_PREVENT_MACRO_SUBSTITUTION () const { return 0; }
    int32_t max BOOST_PREVENT_MACRO_SUBSTITUTION () const { return std::numeric_limits<int32_t>::max BOOST_PREVENT_MACRO_SUBSTITUTION (); }
    
    explicit rand48(int32_t x0 = 1) : lcf(cnv(x0)) { }
    explicit rand48(uint64_t x0) : lcf(x0) { }
    template<class It> rand48(It& first, It last) : lcf(first, last) { }
    // compiler-generated copy ctor and assignment operator are fine
    void seed(int32_t x0 = 1) { lcf.seed(cnv(x0)); }
    void seed(uint64_t x0) { lcf.seed(x0); }
    template<class It> void seed(It& first, It last) { lcf.seed(first,last); }
  
    int32_t operator()() { return static_cast<int32_t>(lcf() >> 17); }
    // by experiment from lrand48()
    static bool validation(int32_t x) { return x == 1993516219; }
  
  #ifndef BOOST_NO_OPERATORS_IN_NAMESPACE
  
  #ifndef BOOST_NO_MEMBER_TEMPLATE_FRIENDS
    template<class CharT,class Traits>
    friend std::basic_ostream<CharT,Traits>&
    operator<<(std::basic_ostream<CharT,Traits>& os, const rand48& r)
    { os << r.lcf; return os; }
  
    template<class CharT,class Traits>
    friend std::basic_istream<CharT,Traits>&
    operator>>(std::basic_istream<CharT,Traits>& is, rand48& r)
    { is >> r.lcf; return is; }
  #endif
  
    friend bool operator==(const rand48& x, const rand48& y)
    { return x.lcf == y.lcf; }
    friend bool operator!=(const rand48& x, const rand48& y)
    { return !(x == y); }
  #else
    // Use a member function; Streamable concept not supported.
    bool operator==(const rand48& rhs) const
    { return lcf == rhs.lcf; }
    bool operator!=(const rand48& rhs) const
    { return !(*this == rhs); }
  #endif
  private:
    random::linear_congruential<uint64_t,
      uint64_t(0xDEECE66DUL) | (uint64_t(0x5) << 32), // xxxxULL is not portable
      0xB, uint64_t(1)<<48, /* unknown */ 0> lcf;
    static uint64_t cnv(int32_t x) 
    { return (static_cast<uint64_t>(x) << 16) | 0x330e;  }
  };
  #endif /* !BOOST_NO_INT64_T && !BOOST_NO_INTEGRAL_INT64_T */
  
  } // namespace boost
  
  #endif // BOOST_RANDOM_LINEAR_CONGRUENTIAL_HPP
  