#ifndef MYSQLCPPAPI_null_h#define MYSQLCPPAPI_null_h#include "mysqlcppapi/exceptions/ex_BadNullConversion.h"#include <iostream>namespace mysqlcppapi{//! with_class = Null//TODO: What's this Null stuff all about? murrayc.class null_type{public:  template <class Type> operator Type ()  {    throw ex_BadNullConversion();  }}; static const null_type null = null_type();//: Type to use for the behavior parameter for *Null<>*class NullisNull{public:  static null_type null_is() {return null_type();}  static std::ostream&  null_ostr(std::ostream& o) {o << "(NULL)"; return o;}};//: Type to use for the behavior parameter for *Null<>*class NullisZero{public:  static int   null_is() {return 0;}  static std::ostream& null_ostr(std::ostream &o) {o << 0; return o;}};//: Type to use for the behavior parameter for *Null<>*class NullisBlank{public:  static const char* null_is() {return "";}  static std::ostream& null_ostr(std::ostream &o) {o << ""; return o;}};//: Container class for holding null types.template <class Type, class Behavior = NullisNull>class Null {public:  Type data;  bool is_null;  typedef Type value_type;public:  Null () {}   Null (Type x) : data(x), is_null(false) {}      Null (const null_type& n) : is_null(true) {}   //: Gives Null the null value  // Note: the global const *null* (not NULL) is of value null_type thus   // you can say something like *Null<Type> x = null*.  operator Type& () {     if (is_null) return data = Behavior::null_is();    else return data; }     Null& operator = (const Type& x) {data = x; is_null = false; return *this;}     Null& operator = (const null_type&) {is_null = true; return *this;}  };//: OEP - Specialization for <void>template <> class Null<void> {public:  bool is_null;  typedef void value_type;public:  Null () : is_null(false) {}      Null (const null_type&) : is_null(true) {}   //: Gives Null the null value  // Note: the global const *null* (not NULL) is of value null_type thus   // you can say something like *Null<Type> x = null*.    Null& operator = (const null_type&) {is_null = true; return *this;}  };template <class Type, class Behavior>inline std::ostream& operator << (std::ostream &o, const Null<Type,Behavior> &n){  if (n.is_null) return Behavior::null_ostr(o);  else return o << n.data;}} //namespace#endif  // MYSQLCPPAPI_null_h