text: #ifndef _DATE_TIME_INT_ADAPTER_HPP__
  #define _DATE_TIME_INT_ADAPTER_HPP__
  
  /* Copyright (c) 2002,2003 CrystalClear Software, Inc.
   * Use, modification and distribution is subject to the 
   * Boost Software License, Version 1.0. (See accompanying
   * file LICENSE-1.0 or http://www.boost.org/LICENSE-1.0)
   * Author: Jeff Garland, Bart Garst
   * $Date: 2007/02/12 18:25:13 $
   */
  
  
  #include "boost/config.hpp"
  #include "boost/limits.hpp" //work around compilers without limits
  #include "boost/date_time/special_defs.hpp"
  #include "boost/date_time/locale_config.hpp"
  #include <iostream>
  
  namespace boost {
  namespace date_time {
  
  
  //! Adapter to create integer types with +-infinity, and not a value
  /*! This class is used internally in counted date/time representations.
   *  It adds the floating point like features of infinities and
   *  not a number. It also provides mathmatical operations with
   *  consideration to special values following these rules:
   *@code
   *  +infinity  -  infinity  == Not A Number (NAN)
   *   infinity  *  non-zero  == infinity
   *   infinity  *  zero      == NAN
   *  +infinity  * -integer   == -infinity
   *   infinity  /  infinity  == NAN
   *   infinity  *  infinity  == infinity 
   *@endcode 
   */
  template<typename int_type_>
  class int_adapter {
  public:
    typedef int_type_ int_type;
    int_adapter(int_type v) :
      value_(v)
    {}
    static bool has_infinity()
    {
      return  true;
    }
    static const int_adapter  pos_infinity()
    {
      return (::std::numeric_limits<int_type>::max)();
    }
    static const int_adapter  neg_infinity()
    {
      return (::std::numeric_limits<int_type>::min)();
    }
    static const int_adapter  not_a_number()
    {
      return (::std::numeric_limits<int_type>::max)()-1;
    }
    static  int_adapter max BOOST_PREVENT_MACRO_SUBSTITUTION ()
    {
      return (::std::numeric_limits<int_type>::max)()-2;
    }
    static  int_adapter min BOOST_PREVENT_MACRO_SUBSTITUTION ()
    {
      return (::std::numeric_limits<int_type>::min)()+1;
    }
    static int_adapter from_special(special_values sv)
    {
      switch (sv) {
      case not_a_date_time: return not_a_number();
      case neg_infin:       return neg_infinity();
      case pos_infin:       return pos_infinity();
      case max_date_time:   return (max)();
      case min_date_time:   return (min)();
      default:              return not_a_number();
      }
    }
    static bool is_inf(int_type v)
    {
      return (v == neg_infinity().as_number() ||
              v == pos_infinity().as_number());
    }
    static bool is_neg_inf(int_type v)
    {
      return (v == neg_infinity().as_number());
    }
    static bool is_pos_inf(int_type v)
    {
      return (v == pos_infinity().as_number());
    }
    static bool is_not_a_number(int_type v)
    {
      return (v == not_a_number().as_number());
    }
    //! Returns either special value type or is_not_special
    static special_values to_special(int_type v)
    {
      if (is_not_a_number(v)) return not_a_date_time;
      if (is_neg_inf(v)) return neg_infin;
      if (is_pos_inf(v)) return pos_infin;
      return not_special;
    }
  
    //-3 leaves room for representations of infinity and not a date
    static  int_type maxcount()
    {
      return (::std::numeric_limits<int_type>::max)()-3;
    }
    bool is_infinity() const
    {
      return (value_ == neg_infinity().as_number() ||
              value_ == pos_infinity().as_number());
    }
    bool is_pos_infinity()const
    {
      return(value_ == pos_infinity().as_number());
    }
    bool is_neg_infinity()const
    {
      return(value_ == neg_infinity().as_number());
    }
    bool is_nan() const
    {
      return (value_ == not_a_number().as_number());
    }
    bool is_special() const
    {
      return(is_infinity() || is_nan()); 
    }
    bool operator==(const int_adapter& rhs) const
    {
      return (compare(rhs) == 0);
    }
    bool operator==(const int& rhs) const
    {
      // quiets compiler warnings
      bool is_signed = std::numeric_limits<int_type>::is_signed;
      if(!is_signed)
      {
        if(is_neg_inf(value_) && rhs == 0)
        {
          return false;
        }
      }
      return (compare(rhs) == 0);
    }
    bool operator!=(const int_adapter& rhs) const
    {
      return (compare(rhs) != 0);
    }
    bool operator!=(const int& rhs) const
    {
      // quiets compiler warnings
      bool is_signed = std::numeric_limits<int_type>::is_signed;
      if(!is_signed)
      {
        if(is_neg_inf(value_) && rhs == 0)
        {
          return true;
        }
      }
      return (compare(rhs) != 0);
    }
    bool operator<(const int_adapter& rhs) const
    {
      return (compare(rhs) == -1);
    }
    bool operator<(const int& rhs) const
    {
      // quiets compiler warnings
      bool is_signed = std::numeric_limits<int_type>::is_signed;
      if(!is_signed)
      {
        if(is_neg_inf(value_) && rhs == 0)
        {
          return true;
        }
      }
      return (compare(rhs) == -1);
    }
    bool operator>(const int_adapter& rhs) const
    {
      return (compare(rhs) == 1);
    }
    int_type as_number() const
    {
      return value_;
    }
    //! Returns either special value type or is_not_special
    special_values as_special() const
    {
      return int_adapter::to_special(value_);
    }
    //creates nasty ambiguities
  //   operator int_type() const
  //   {
  //     return value_;
  //   }
  
    /*! Operator allows for adding dissimilar int_adapter types.
     * The return type will match that of the the calling object's type */
    template<class rhs_type>
    inline
    int_adapter operator+(const int_adapter<rhs_type>& rhs) const
    {
      if(is_special() || rhs.is_special())
      {
        if (is_nan() || rhs.is_nan()) 
        {
          return int_adapter::not_a_number();
        }
        if((is_pos_inf(value_) && rhs.is_neg_inf(rhs.as_number())) ||
        (is_neg_inf(value_) && rhs.is_pos_inf(rhs.as_number())) )
        {
          return int_adapter::not_a_number();
        }
        if (is_infinity()) 
        {
          return *this;
        }
        if (rhs.is_pos_inf(rhs.as_number())) 
        {
          return int_adapter::pos_infinity();
        }
        if (rhs.is_neg_inf(rhs.as_number())) 
        {
          return int_adapter::neg_infinity();
        }
      }
      return int_adapter<int_type>(value_ + rhs.as_number());
    }
  
    int_adapter operator+(const int_type rhs) const
    {
      if(is_special())
      {
        if (is_nan()) 
        {
          return int_adapter<int_type>(not_a_number());
        }
        if (is_infinity()) 
        {
          return *this;
        }
      }
      return int_adapter<int_type>(value_ + rhs);
    }
    
    /*! Operator allows for subtracting dissimilar int_adapter types.
     * The return type will match that of the the calling object's type */
    template<class rhs_type>
    inline
    int_adapter operator-(const int_adapter<rhs_type>& rhs)const
    {
      if(is_special() || rhs.is_special())
      {
        if (is_nan() || rhs.is_nan()) 
        {
          return int_adapter::not_a_number();
        }
        if((is_pos_inf(value_) && rhs.is_pos_inf(rhs.as_number())) ||
           (is_neg_inf(value_) && rhs.is_neg_inf(rhs.as_number())) )
        {
          return int_adapter::not_a_number();
        }
        if (is_infinity()) 
        {
          return *this;
        }
        if (rhs.is_pos_inf(rhs.as_number())) 
        {
          return int_adapter::neg_infinity();
        }
        if (rhs.is_neg_inf(rhs.as_number())) 
        {
          return int_adapter::pos_infinity();
        }
      }
      return int_adapter<int_type>(value_ - rhs.as_number());
    }
    int_adapter operator-(const int_type rhs) const
    {
      if(is_special())
      {
        if (is_nan()) 
        {
          return int_adapter<int_type>(not_a_number());
        }
        if (is_infinity()) 
        {
          return *this;
        }
      }
      return int_adapter<int_type>(value_ - rhs);
    }
  
    // should templatize this to be consistant with op +-
    int_adapter operator*(const int_adapter& rhs)const
    {
      if(this->is_special() || rhs.is_special())
      {
        return mult_div_specials(rhs);
      }
      return int_adapter<int_type>(value_ * rhs.value_);
    }
    /*! Provided for cases when automatic conversion from 
     * 'int' to 'int_adapter' causes incorrect results. */
    int_adapter operator*(const int rhs) const
    {
      if(is_special())
      {
        return mult_div_specials(rhs);
      }
      return int_adapter<int_type>(value_ * rhs);
    }
  
    // should templatize this to be consistant with op +-
    int_adapter operator/(const int_adapter& rhs)const
    {
      if(this->is_special() || rhs.is_special())
      {
        if(is_infinity() && rhs.is_infinity())
        {
          return int_adapter<int_type>(not_a_number());
        }
        if(rhs != 0)
        {
          return mult_div_specials(rhs);
        }
        else { // let divide by zero blow itself up
          return int_adapter<int_type>(value_ / rhs.value_);
        }
      }
      return int_adapter<int_type>(value_ / rhs.value_);
    }
    /*! Provided for cases when automatic conversion from 
     * 'int' to 'int_adapter' causes incorrect results. */
    int_adapter operator/(const int rhs) const
    {
      if(is_special() && rhs != 0)
      {
        return mult_div_specials(rhs);
      }
      return int_adapter<int_type>(value_ / rhs);
    }
  
    // should templatize this to be consistant with op +-
    int_adapter operator%(const int_adapter& rhs)const
    {
      if(this->is_special() || rhs.is_special())
      {
        if(is_infinity() && rhs.is_infinity())
        {
          return int_adapter<int_type>(not_a_number());
        }
        if(rhs != 0)
        {
          return mult_div_specials(rhs);
        }
        else { // let divide by zero blow itself up
          return int_adapter<int_type>(value_ % rhs.value_);
        }
      }
      return int_adapter<int_type>(value_ % rhs.value_);
    }
    /*! Provided for cases when automatic conversion from 
     * 'int' to 'int_adapter' causes incorrect results. */
    int_adapter operator%(const int rhs) const
    {
      if(is_special() && rhs != 0)
      {
        return mult_div_specials(rhs);
      }
      return int_adapter<int_type>(value_ % rhs);
    }
  private:
    int_type value_;
    
    //! returns -1, 0, 1, or 2 if 'this' is <, ==, >, or 'nan comparison' rhs
    int compare(const int_adapter& rhs)const
    {
      if(this->is_special() || rhs.is_special())
      {
        if(this->is_nan() || rhs.is_nan()) {
          if(this->is_nan() && rhs.is_nan()) {
            return 0; // equal
          }
          else {
            return 2; // nan
          }
        }
        if((is_neg_inf(value_) && !is_neg_inf(rhs.value_)) ||
           (is_pos_inf(rhs.value_) && !is_pos_inf(value_)) )
          {
            return -1; // less than
          }
        if((is_pos_inf(value_) && !is_pos_inf(rhs.value_)) ||
           (is_neg_inf(rhs.value_) && !is_neg_inf(value_)) ) {
          return 1; // greater than
        }
      }
      if(value_ < rhs.value_) return -1;
      if(value_ > rhs.value_) return 1;
      // implied-> if(value_ == rhs.value_) 
      return 0;
    }
    /* When multiplying and dividing with at least 1 special value
     * very simmilar rules apply. In those cases where the rules
     * are different, they are handled in the respective operator 
     * function. */
    //! Assumes at least 'this' or 'rhs' is a special value
    int_adapter mult_div_specials(const int_adapter& rhs)const
    {
      int min_value; 
      // quiets compiler warnings
      bool is_signed = std::numeric_limits<int_type>::is_signed;
      if(is_signed) {
        min_value = 0;
      }
      else {
        min_value = 1;// there is no zero with unsigned
      }
      if(this->is_nan() || rhs.is_nan()) {
        return int_adapter<int_type>(not_a_number());
      }
      if((*this > 0 && rhs > 0) || (*this < min_value && rhs < min_value)) {
          return int_adapter<int_type>(pos_infinity());
      }
      if((*this > 0 && rhs < min_value) || (*this < min_value && rhs > 0)) {
          return int_adapter<int_type>(neg_infinity());
      }
      //implied -> if(this->value_ == 0 || rhs.value_ == 0)
      return int_adapter<int_type>(not_a_number());
    }
    /* Overloaded function necessary because of special
     * situation where int_adapter is instantiated with 
     * 'unsigned' and func is called with negative int.
     * It would produce incorrect results since 'unsigned'
     * wraps around when initialized with a negative value */
    //! Assumes 'this' is a special value
    int_adapter mult_div_specials(const int& rhs) const
    {
      int min_value; 
      // quiets compiler warnings
      bool is_signed = std::numeric_limits<int_type>::is_signed;
      if(is_signed) {
        min_value = 0;
      }
      else {
        min_value = 1;// there is no zero with unsigned
      }
      if(this->is_nan()) {
        return int_adapter<int_type>(not_a_number());
      }
      if((*this > 0 && rhs > 0) || (*this < min_value && rhs < 0)) {
          return int_adapter<int_type>(pos_infinity());
      }
      if((*this > 0 && rhs < 0) || (*this < min_value && rhs > 0)) {
          return int_adapter<int_type>(neg_infinity());
      }
      //implied -> if(this->value_ == 0 || rhs.value_ == 0)
      return int_adapter<int_type>(not_a_number());
    }
    
  };
  
  #ifndef BOOST_DATE_TIME_NO_LOCALE
    /*! Expected output is either a numeric representation 
     * or a special values representation.<BR> 
     * Ex. "12", "+infinity", "not-a-number", etc. */
    //template<class charT = char, class traits = std::traits<charT>, typename int_type>
    template<class charT, class traits, typename int_type>
    inline
    std::basic_ostream<charT, traits>& 
    operator<<(std::basic_ostream<charT, traits>& os, const int_adapter<int_type>& ia)
    {
      if(ia.is_special()) {
        // switch copied from date_names_put.hpp
        switch(ia.as_special())
          {
        case not_a_date_time:
          os << "not-a-number";
          break;
        case pos_infin:
          os << "+infinity";
          break;
        case neg_infin:
          os << "-infinity";
          break;
        default:
          os << "";
        }
      }
      else {
        os << ia.as_number(); 
      }
      return os;
    }
  #endif
  
  
  } } //namespace date_time
  
  
  
  #endif
  