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tristate.h

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#ifndef ___TRISTATE_H___
#define ___TRISTATE_H___

#include <fstream>
#include <cassert>
#include <string>
using std::string;
#include <strstream>


enum Tristate {Uninitialized=-1,False=false,True=true};


/* Double-check assumption */
// check is not allowed under ISO C++
//#if (false!=0)
//#error 'false' must denote zero
//#endif



inline std::ostream& operator<<(std::ostream &s, const Tristate& t) {
  switch(t){
  case Uninitialized: return s << "Uninitialized";  
  case False:         return s << "False";          
  case True:          return s << "True";          
  default:            return s << int(t); // Unknown value
  }
}


inline std::istream& operator>>(std::istream &s, Tristate& t) {
  string r;
  s >> r;
  if      (r == "Uninitialized") t=Uninitialized;
  else if (r == "False")         t=False;
  else if (r == "True")          t=True;
  else {
    std::istrstream ss(r.c_str(),r.length());
    int x=0;
    ss >> x;
    t=Tristate(x);
  }
  
  return s;
}

#endif /* ___TRISTATE_H___ */

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