ConfiguredValue.h

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/* emacs: this is -*- c++ -*- */
 
#ifndef IDTPM2_CONFIGUREDVALUE_H
#define IDTPM2_CONFIGUREDVALUE_H
 
 
#include <iostream>
 
#define              GENERATOR(OP) { if ( !isset() ) return UnsetResult; return m_value OP a; }
 
#define     OPERATOR_GENERATOR(OP)        template<typename U> bool operator OP ( const U& a ) const GENERATOR(OP)
#define REV_OPERATOR_GENERATOR(OP, REVOP) template<typename T, typename U> bool operator OP ( const U& a, const ConfiguredValue<T>& p ) { return p REVOP a; }
 
template<typename T, bool UnsetResult=false>
struct ConfiguredValue {
 
  ConfiguredValue() : m_set(false), m_value(0)  {  } 
  ConfiguredValue( const T& v ) : m_set(true), m_value(v) {  }
  
  ConfiguredValue( const ConfiguredValue& c ) = default; 
 
  ConfiguredValue& operator=(const ConfiguredValue&) = default;
  
  operator T&()             { return m_value; }
  operator const T&() const { return m_value; }

  explicit operator bool() const { return isset(); }
  
  bool    isset() const { return m_set; }
 
  template<typename U>
  ConfiguredValue<T>& operator=(const U& a ) {
    m_value = a;
    m_set = true;
    return *this;
  }
 
  OPERATOR_GENERATOR(==)
  OPERATOR_GENERATOR(!=)
  OPERATOR_GENERATOR(<=)
  OPERATOR_GENERATOR(>=)
  OPERATOR_GENERATOR(<)
  OPERATOR_GENERATOR(>)
  
private:
  
  bool m_set; 
 
  T    m_value;
 
};
 
 
REV_OPERATOR_GENERATOR(==,==)
REV_OPERATOR_GENERATOR(!=,!=)
REV_OPERATOR_GENERATOR(<=,>=)
REV_OPERATOR_GENERATOR(>=,<=)
REV_OPERATOR_GENERATOR(<,>)
REV_OPERATOR_GENERATOR(>,<)
 
 
template<typename T, bool UnsetResult=false>
std::ostream& operator<<( std::ostream& s, const ConfiguredValue<T>& p ) {
  if (p.isset()) return s << (T)p;
  return s << "not set";
}
 
#endif  // IDTPM2_CONFIGUREDVALUE_H