libstdc++-v3/include/tr2/bool_set

// TR2 <bool_set> -*- C++ -*-

// Copyright (C) 2009-2025 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.

// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.

// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
// <http://www.gnu.org/licenses/>.

/** @file tr2/bool_set
 *  This is a TR2 C++ Library header.
 */

#ifndef _GLIBCXX_TR2_BOOL_SET
#define _GLIBCXX_TR2_BOOL_SET 1

#ifdef _GLIBCXX_SYSHDR
#pragma GCC system_header
#endif

#include <typeinfo>
#include <iostream>

namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION

namespace tr2
{
  /**
   *  bool_set
   *
   *  See N2136, Bool_set: multi-valued logic
   *  by Hervé Brönnimann, Guillaume Melquiond, Sylvain Pion.
   *
   *  The implicit conversion to bool is slippery!  I may use the new
   *  explicit conversion.  This has been specialized in the language
   *  so that in contexts requiring a bool the conversion happens
   *  implicitly.  Thus most objections should be eliminated.
   */
  class bool_set
  {
  public:

    ///  Default constructor.
    constexpr bool_set() : _M_b(_S_false) { }

    ///  Constructor from bool.
    constexpr bool_set(bool __t) : _M_b(_Bool_set_val(__t)) { }

    // I'm not sure about this.
    bool contains(bool_set __b) const
    { return this->is_singleton() && this->equals(__b); }

    ///  Return true if states are equal.
    bool equals(bool_set __b) const
    { return __b._M_b == _M_b; }

    ///  Return true if this is empty.
    bool is_emptyset() const
    { return _M_b == _S_empty; }

    ///  Return true if this is indeterminate.
    bool is_indeterminate() const
    { return _M_b == _S_indet; }

    ///  Return true if this is false or true (normal boolean).
    bool is_singleton() const
    { return _M_b == _S_false || _M_b == _S_true_; }

    ///  Conversion to bool.
    //explicit
    operator bool() const
    {
      if (! is_singleton())
	throw std::bad_cast();
      return _M_b;
    }

    ///
    static bool_set indeterminate()
    {
      bool_set __b;
      __b._M_b = _S_indet;
      return __b;
    }

    ///
    static bool_set emptyset()
    {
      bool_set __b;
      __b._M_b = _S_empty;
      return __b;
    }

    friend bool_set
    operator!(bool_set __b)
    { return __b._M_not(); }

    friend bool_set
    operator^(bool_set __s, bool_set __t)
    { return __s._M_xor(__t); }

    friend bool_set
    operator|(bool_set __s, bool_set __t)
    { return __s._M_or(__t); }

    friend bool_set
    operator&(bool_set __s, bool_set __t)
    { return __s._M_and(__t); }

    friend bool_set
    operator==(bool_set __s, bool_set __t)
    { return __s._M_eq(__t); }


    //  These overloads replace the facet additions in the paper!

    template<typename CharT, typename Traits>
      friend std::basic_ostream<CharT, Traits>&
      operator<<(std::basic_ostream<CharT, Traits>& __out, bool_set __b)
      {
	int __a = __b._M_b;
	__out << __a;
      }

    template<typename CharT, typename Traits>
      friend std::basic_istream<CharT, Traits>&
      operator>>(std::basic_istream<CharT, Traits>& __in, bool_set& __b)
      {
	long __c;
	__in >> __c;
	if (__c >= _S_false && __c < _S_empty)
	  __b._M_b = static_cast<_Bool_set_val>(__c);
      }

  private:

    ///
    enum _Bool_set_val: unsigned char
    {
      _S_false = 0,
      _S_true_ = 1,
      _S_indet = 2,
      _S_empty = 3
    };

    ///  Bool set state.
    _Bool_set_val _M_b;

    ///
    bool_set(_Bool_set_val __c) : _M_b(__c) { }

    ///
    bool_set _M_not() const
    { return _S_not[this->_M_b]; }

    ///
    bool_set _M_xor(bool_set __b) const
    { return _S_xor[this->_M_b][__b._M_b]; }

    ///
    bool_set _M_or(bool_set __b) const
    { return _S_or[this->_M_b][__b._M_b]; }

    ///
    bool_set _M_and(bool_set __b) const
    { return _S_and[this->_M_b][__b._M_b]; }

    ///
    bool_set _M_eq(bool_set __b) const
    { return _S_eq[this->_M_b][__b._M_b]; }

    ///
    static _Bool_set_val _S_not[4];

    ///
    static _Bool_set_val _S_xor[4][4];

    ///
    static _Bool_set_val _S_or[4][4];

    ///
    static _Bool_set_val _S_and[4][4];

    ///
    static _Bool_set_val _S_eq[4][4];
  };

  //  20.2.3.2 bool_set values

  inline bool
  contains(bool_set __s, bool_set __t)
  { return __s.contains(__t); }

  inline bool
  equals(bool_set __s, bool_set __t)
  { return __s.equals(__t); }

  inline bool
  is_emptyset(bool_set __b)
  { return __b.is_emptyset(); }

  inline bool
  is_indeterminate(bool_set __b)
  { return __b.is_indeterminate(); }

  inline bool
  is_singleton(bool_set __b)
  { return __b.is_singleton(); }

  inline bool
  certainly(bool_set __b)
  { return ! __b.contains(false); }

  inline bool
  possibly(bool_set __b)
  { return __b.contains(true); }


  //  20.2.3.3 bool_set set operations

  inline bool_set
  set_union(bool __s, bool_set __t)
  { return bool_set(__s) | __t; }

  inline bool_set
  set_union(bool_set __s, bool __t)
  { return __s | bool_set(__t); }

  inline bool_set
  set_union(bool_set __s, bool_set __t)
  { return __s | __t; }

  inline bool_set
  set_intersection(bool __s, bool_set __t)
  { return bool_set(__s) & __t; }

  inline bool_set
  set_intersection(bool_set __s, bool __t)
  { return __s & bool_set(__t); }

  inline bool_set
  set_intersection(bool_set __s, bool_set __t)
  { return __s & __t; }

  inline bool_set
  set_complement(bool_set __b)
  { return ! __b; }


  //  20.2.3.4 bool_set logical operators

  inline bool_set
  operator^(bool __s, bool_set __t)
  { return bool_set(__s) ^ __t; }

  inline bool_set
  operator^(bool_set __s, bool __t)
  { return __s ^ bool_set(__t); }

  inline bool_set
  operator|(bool __s, bool_set __t)
  { return bool_set(__s) | __t; }

  inline bool_set
  operator|(bool_set __s, bool __t)
  { return __s | bool_set(__t); }

  inline bool_set
  operator&(bool __s, bool_set __t)
  { return bool_set(__s) & __t; }

  inline bool_set
  operator&(bool_set __s, bool __t)
  { return __s & bool_set(__t); }


  //  20.2.3.5 bool_set relational operators

  inline bool_set
  operator==(bool __s, bool_set __t)
  { return bool_set(__s) == __t; }

  inline bool_set
  operator==(bool_set __s, bool __t)
  { return __s == bool_set(__t); }

  inline bool_set
  operator!=(bool __s, bool_set __t)
  { return ! (__s == __t); }

  inline bool_set
  operator!=(bool_set __s, bool __t)
  { return ! (__s == __t); }

  inline bool_set
  operator!=(bool_set __s, bool_set __t)
  { return ! (__s == __t); }
}

_GLIBCXX_END_NAMESPACE_VERSION
}

#include <tr2/bool_set.tcc>

#endif // _GLIBCXX_TR2_BOOL_SET