tribool.h

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// Three-state boolean logic library

// Copyright Douglas Gregor 2002-2004. Use, modification and
// distribution is subject to the Boost Software License, Version
// 1.0. (See accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)

// Modifications by Orxonox to shape the third state into 'dontcare' instead
// of 'indeterminate'. The difference is that 'dontcare' is actually a value
// so that (dontcare == dontcare).
// Also removed all logic operators except for == and !=
// Added C++11 constexpr


// For more information, see http://www.boost.org
#ifndef ORXONOX_TRIBOOL_H
#define ORXONOX_TRIBOOL_H

namespace orxonox {

struct dontcare_keyword_t {};

constexpr dontcare_keyword_t dontcare = dontcare_keyword_t();

class tribool
{
public:
  constexpr tribool() : value(false_value) {}

  constexpr tribool(bool value) : value(value? true_value : false_value) {}

  constexpr tribool(dontcare_keyword_t) : value(dontcare_value) {}

  constexpr bool operator==(tribool y) const
  {
    return (this->value == y.value);
  }

  constexpr bool operator==(bool y) const { return (*this) == tribool(y); }

  constexpr bool operator==(dontcare_keyword_t) const
  { return tribool(dontcare) == (*this); }

  constexpr bool operator!=(tribool y) const
  {
    return !((*this) == y);
  }

  constexpr bool operator!=(bool y) const { return (*this) != tribool(y); }

  constexpr bool operator!=(dontcare_keyword_t) const
  { return (*this) != tribool(dontcare); }

  enum value_t { false_value, true_value, dontcare_value } value;
};

constexpr bool operator==(bool x, tribool y) { return tribool(x) == y; }

constexpr bool operator==(dontcare_keyword_t, tribool x)
{ return tribool(dontcare) == x; }

constexpr bool operator!=(bool x, tribool y) { return tribool(x) != y; }

constexpr bool operator!=(dontcare_keyword_t, tribool x)
{ return tribool(dontcare) != x; }

} // end namespace orxonox

#endif // ORXONOX_TRIBOOL_H