alpar@162: // -*- mode:C++ -*-
alpar@162: 
alpar@162: #ifndef HUGO_INVALID_H
alpar@162: #define HUGO_INVALID_H
alpar@162: 
alpar@242: ///\file
alpar@242: ///\brief Definition of INVALID.
alpar@242: 
alpar@162: namespace hugo {
alpar@162: 
alpar@162:   /// Dummy type to make it easier to make invalid iterators.
alpar@162:   
alpar@162:   /// See \ref INVALID, how to use it.
alpar@162:   
alpar@412:   struct Invalid {
alpar@412:   public:
alpar@412:     bool operator==(Invalid) { return true;  }
alpar@412:     bool operator!=(Invalid) { return false; }
alpar@412:     bool operator< (Invalid) { return false; }
alpar@412:   };
alpar@162:   
alpar@162:   /// Invalid iterators.
alpar@162:   
alpar@162:   /// \ref Invalid is a global type that converts to each iterator
alpar@162:   /// in such a way that the value of the target iterator will be invalid.
alpar@184: 
alpar@184:   // It is also used to convert the \c INVALID constant to the
alpar@184:   // node iterator that makes is possible to write 
alpar@184: 
alpar@165:   //extern Invalid INVALID;
alpar@162: 
klao@169:   //const Invalid &INVALID = *(Invalid *)0;
klao@169:   const Invalid INVALID = Invalid();
alpar@162: 
marci@389: } //namespace hugo
alpar@162: 
alpar@162: #endif
alpar@162: