sl@0: // Three-state boolean logic library
sl@0: 
sl@0: // Copyright Douglas Gregor 2002-2004. Use, modification and
sl@0: // distribution is subject to the Boost Software License, Version
sl@0: // 1.0. (See accompanying file LICENSE_1_0.txt or copy at
sl@0: // http://www.boost.org/LICENSE_1_0.txt)
sl@0: 
sl@0: 
sl@0: // For more information, see http://www.boost.org
sl@0: #ifndef BOOST_LOGIC_TRIBOOL_HPP
sl@0: #define BOOST_LOGIC_TRIBOOL_HPP
sl@0: 
sl@0: #include <boost/logic/tribool_fwd.hpp>
sl@0: #include <boost/config.hpp>
sl@0: #include <boost/detail/workaround.hpp>
sl@0: 
sl@0: #if BOOST_WORKAROUND(_MSC_VER, >= 1200)
sl@0: #  pragma once
sl@0: #endif
sl@0: 
sl@0: namespace boost { namespace logic {
sl@0: 
sl@0: /// INTERNAL ONLY
sl@0: namespace detail {
sl@0: /**
sl@0:  * INTERNAL ONLY
sl@0:  *
sl@0:  * \brief A type used only to uniquely identify the 'indeterminate'
sl@0:  * function/keyword.
sl@0:  */
sl@0: struct indeterminate_t
sl@0: {
sl@0: #if BOOST_WORKAROUND(__BORLANDC__, < 0x0600)
sl@0:   char dummy_; // BCB would use 8 bytes by default
sl@0: #endif
sl@0: };
sl@0: 
sl@0: } // end namespace detail
sl@0: 
sl@0: /**
sl@0:  * INTERNAL ONLY
sl@0:  * The type of the 'indeterminate' keyword. This has the same type as the
sl@0:  * function 'indeterminate' so that we can recognize when the keyword is
sl@0:  * used.
sl@0:  */
sl@0: typedef bool (*indeterminate_keyword_t)(tribool, detail::indeterminate_t);
sl@0: 
sl@0: /**
sl@0:  * \brief Keyword and test function for the indeterminate tribool value
sl@0:  *
sl@0:  * The \c indeterminate function has a dual role. It's first role is
sl@0:  * as a unary function that tells whether the tribool value is in the
sl@0:  * "indeterminate" state. It's second role is as a keyword
sl@0:  * representing the indeterminate (just like "true" and "false"
sl@0:  * represent the true and false states). If you do not like the name
sl@0:  * "indeterminate", and would prefer to use a different name, see the
sl@0:  * macro \c BOOST_TRIBOOL_THIRD_STATE.
sl@0:  *
sl@0:  * \returns <tt>x.value == tribool::indeterminate_value</tt>
sl@0:  * \throws nothrow
sl@0:  */
sl@0: inline bool
sl@0: indeterminate(tribool x,
sl@0:               detail::indeterminate_t dummy = detail::indeterminate_t());
sl@0: 
sl@0: /**
sl@0:  * \brief A 3-state boolean type.
sl@0:  *
sl@0:  * 3-state boolean values are either true, false, or
sl@0:  * indeterminate.
sl@0:  */
sl@0: class tribool
sl@0: {
sl@0: private:
sl@0:   /// INTERNAL ONLY
sl@0:   struct dummy {
sl@0:     void nonnull() {};
sl@0:   };
sl@0: 
sl@0:   typedef void (dummy::*safe_bool)();
sl@0: 
sl@0: public:
sl@0:   /**
sl@0:    * Construct a new 3-state boolean value with the value 'false'.
sl@0:    *
sl@0:    * \throws nothrow
sl@0:    */
sl@0:   tribool() : value(false_value) {}
sl@0: 
sl@0:   /**
sl@0:    * Construct a new 3-state boolean value with the given boolean
sl@0:    * value, which may be \c true or \c false.
sl@0:    *
sl@0:    * \throws nothrow
sl@0:    */
sl@0:   tribool(bool value) : value(value? true_value : false_value) {}
sl@0: 
sl@0:   /**
sl@0:    * Construct a new 3-state boolean value with an indeterminate value.
sl@0:    *
sl@0:    * \throws nothrow
sl@0:    */
sl@0:   tribool(indeterminate_keyword_t) : value(indeterminate_value) {}
sl@0: 
sl@0:   /**
sl@0:    * Use a 3-state boolean in a boolean context. Will evaluate true in a
sl@0:    * boolean context only when the 3-state boolean is definitely true.
sl@0:    *
sl@0:    * \returns true if the 3-state boolean is true, false otherwise
sl@0:    * \throws nothrow
sl@0:    */
sl@0:   operator safe_bool() const
sl@0:   {
sl@0:     return value == true_value? &dummy::nonnull : 0;
sl@0:   }
sl@0: 
sl@0:   /**
sl@0:    * The actual stored value in this 3-state boolean, which may be false, true,
sl@0:    * or indeterminate.
sl@0:    */
sl@0:   enum value_t { false_value, true_value, indeterminate_value } value;
sl@0: };
sl@0: 
sl@0: // Check if the given tribool has an indeterminate value. Also doubles as a
sl@0: // keyword for the 'indeterminate' value
sl@0: inline bool indeterminate(tribool x, detail::indeterminate_t)
sl@0: {
sl@0:   return x.value == tribool::indeterminate_value;
sl@0: }
sl@0: 
sl@0: /** @defgroup logical Logical operations
sl@0:  */
sl@0: //@{
sl@0: /**
sl@0:  * \brief Computes the logical negation of a tribool
sl@0:  *
sl@0:  * \returns the logical negation of the tribool, according to the
sl@0:  * table:
sl@0:  *  <table border=1>
sl@0:  *    <tr>
sl@0:  *      <th><center><code>!</code></center></th>
sl@0:  *      <th/>
sl@0:  *    </tr>
sl@0:  *    <tr>
sl@0:  *      <th><center>false</center></th>
sl@0:  *      <td><center>true</center></td>
sl@0:  *    </tr>
sl@0:  *    <tr>
sl@0:  *      <th><center>true</center></th>
sl@0:  *      <td><center>false</center></td>
sl@0:  *    </tr>
sl@0:  *    <tr>
sl@0:  *      <th><center>indeterminate</center></th>
sl@0:  *      <td><center>indeterminate</center></td>
sl@0:  *    </tr>
sl@0:  *  </table>
sl@0:  * \throws nothrow
sl@0:  */
sl@0: inline tribool operator!(tribool x)
sl@0: {
sl@0:   return x.value == tribool::false_value? tribool(true)
sl@0:         :x.value == tribool::true_value? tribool(false)
sl@0:         :tribool(indeterminate);
sl@0: }
sl@0: 
sl@0: /**
sl@0:  * \brief Computes the logical conjuction of two tribools
sl@0:  *
sl@0:  * \returns the result of logically ANDing the two tribool values,
sl@0:  * according to the following table:
sl@0:  *       <table border=1>
sl@0:  *           <tr>
sl@0:  *             <th><center><code>&amp;&amp;</code></center></th>
sl@0:  *             <th><center>false</center></th>
sl@0:  *             <th><center>true</center></th>
sl@0:  *             <th><center>indeterminate</center></th>
sl@0:  *           </tr>
sl@0:  *           <tr>
sl@0:  *             <th><center>false</center></th>
sl@0:  *             <td><center>false</center></td>
sl@0:  *             <td><center>false</center></td>
sl@0:  *             <td><center>false</center></td>
sl@0:  *           </tr>
sl@0:  *           <tr>
sl@0:  *             <th><center>true</center></th>
sl@0:  *             <td><center>false</center></td>
sl@0:  *             <td><center>true</center></td>
sl@0:  *             <td><center>indeterminate</center></td>
sl@0:  *           </tr>
sl@0:  *           <tr>
sl@0:  *             <th><center>indeterminate</center></th>
sl@0:  *             <td><center>false</center></td>
sl@0:  *             <td><center>indeterminate</center></td>
sl@0:  *             <td><center>indeterminate</center></td>
sl@0:  *           </tr>
sl@0:  *       </table>
sl@0:  * \throws nothrow
sl@0:  */
sl@0: inline tribool operator&&(tribool x, tribool y)
sl@0: {
sl@0:   if (static_cast<bool>(!x) || static_cast<bool>(!y))
sl@0:     return false;
sl@0:   else if (static_cast<bool>(x) && static_cast<bool>(y))
sl@0:     return true;
sl@0:   else
sl@0:     return indeterminate;
sl@0: }
sl@0: 
sl@0: /**
sl@0:  * \overload
sl@0:  */
sl@0: inline tribool operator&&(tribool x, bool y)
sl@0: { return y? x : tribool(false); }
sl@0: 
sl@0: /**
sl@0:  * \overload
sl@0:  */
sl@0: inline tribool operator&&(bool x, tribool y)
sl@0: { return x? y : tribool(false); }
sl@0: 
sl@0: /**
sl@0:  * \overload
sl@0:  */
sl@0: inline tribool operator&&(indeterminate_keyword_t, tribool x)
sl@0: { return !x? tribool(false) : tribool(indeterminate); }
sl@0: 
sl@0: /**
sl@0:  * \overload
sl@0:  */
sl@0: inline tribool operator&&(tribool x, indeterminate_keyword_t)
sl@0: { return !x? tribool(false) : tribool(indeterminate); }
sl@0: 
sl@0: /**
sl@0:  * \brief Computes the logical disjunction of two tribools
sl@0:  *
sl@0:  * \returns the result of logically ORing the two tribool values,
sl@0:  * according to the following table:
sl@0:  *       <table border=1>
sl@0:  *           <tr>
sl@0:  *             <th><center><code>||</code></center></th>
sl@0:  *             <th><center>false</center></th>
sl@0:  *             <th><center>true</center></th>
sl@0:  *             <th><center>indeterminate</center></th>
sl@0:  *           </tr>
sl@0:  *           <tr>
sl@0:  *             <th><center>false</center></th>
sl@0:  *             <td><center>false</center></td>
sl@0:  *             <td><center>true</center></td>
sl@0:  *             <td><center>indeterminate</center></td>
sl@0:  *           </tr>
sl@0:  *           <tr>
sl@0:  *             <th><center>true</center></th>
sl@0:  *             <td><center>true</center></td>
sl@0:  *             <td><center>true</center></td>
sl@0:  *             <td><center>true</center></td>
sl@0:  *           </tr>
sl@0:  *           <tr>
sl@0:  *             <th><center>indeterminate</center></th>
sl@0:  *             <td><center>indeterminate</center></td>
sl@0:  *             <td><center>true</center></td>
sl@0:  *             <td><center>indeterminate</center></td>
sl@0:  *           </tr>
sl@0:  *       </table>
sl@0:  *  \throws nothrow
sl@0:  */
sl@0: inline tribool operator||(tribool x, tribool y)
sl@0: {
sl@0:   if (static_cast<bool>(!x) && static_cast<bool>(!y))
sl@0:     return false;
sl@0:   else if (static_cast<bool>(x) || static_cast<bool>(y))
sl@0:     return true;
sl@0:   else
sl@0:     return indeterminate;
sl@0: }
sl@0: 
sl@0: /**
sl@0:  * \overload
sl@0:  */
sl@0: inline tribool operator||(tribool x, bool y)
sl@0: { return y? tribool(true) : x; }
sl@0: 
sl@0: /**
sl@0:  * \overload
sl@0:  */
sl@0: inline tribool operator||(bool x, tribool y)
sl@0: { return x? tribool(true) : y; }
sl@0: 
sl@0: /**
sl@0:  * \overload
sl@0:  */
sl@0: inline tribool operator||(indeterminate_keyword_t, tribool x)
sl@0: { return x? tribool(true) : tribool(indeterminate); }
sl@0: 
sl@0: /**
sl@0:  * \overload
sl@0:  */
sl@0: inline tribool operator||(tribool x, indeterminate_keyword_t)
sl@0: { return x? tribool(true) : tribool(indeterminate); }
sl@0: //@}
sl@0: 
sl@0: /**
sl@0:  * \brief Compare tribools for equality
sl@0:  *
sl@0:  * \returns the result of comparing two tribool values, according to
sl@0:  * the following table:
sl@0:  *       <table border=1>
sl@0:  *          <tr>
sl@0:  *            <th><center><code>==</code></center></th>
sl@0:  *            <th><center>false</center></th>
sl@0:  *            <th><center>true</center></th>
sl@0:  *            <th><center>indeterminate</center></th>
sl@0:  *          </tr>
sl@0:  *          <tr>
sl@0:  *            <th><center>false</center></th>
sl@0:  *            <td><center>true</center></td>
sl@0:  *            <td><center>false</center></td>
sl@0:  *            <td><center>indeterminate</center></td>
sl@0:  *          </tr>
sl@0:  *          <tr>
sl@0:  *            <th><center>true</center></th>
sl@0:  *            <td><center>false</center></td>
sl@0:  *            <td><center>true</center></td>
sl@0:  *            <td><center>indeterminate</center></td>
sl@0:  *          </tr>
sl@0:  *          <tr>
sl@0:  *            <th><center>indeterminate</center></th>
sl@0:  *            <td><center>indeterminate</center></td>
sl@0:  *            <td><center>indeterminate</center></td>
sl@0:  *            <td><center>indeterminate</center></td>
sl@0:  *          </tr>
sl@0:  *      </table>
sl@0:  * \throws nothrow
sl@0:  */
sl@0: inline tribool operator==(tribool x, tribool y)
sl@0: {
sl@0:   if (indeterminate(x) || indeterminate(y))
sl@0:     return indeterminate;
sl@0:   else
sl@0:     return x && y || !x && !y;
sl@0: }
sl@0: 
sl@0: /**
sl@0:  * \overload
sl@0:  */
sl@0: inline tribool operator==(tribool x, bool y) { return x == tribool(y); }
sl@0: 
sl@0: /**
sl@0:  * \overload
sl@0:  */
sl@0: inline tribool operator==(bool x, tribool y) { return tribool(x) == y; }
sl@0: 
sl@0: /**
sl@0:  * \overload
sl@0:  */
sl@0: inline tribool operator==(indeterminate_keyword_t, tribool x)
sl@0: { return tribool(indeterminate) == x; }
sl@0: 
sl@0: /**
sl@0:  * \overload
sl@0:  */
sl@0: inline tribool operator==(tribool x, indeterminate_keyword_t)
sl@0: { return tribool(indeterminate) == x; }
sl@0: 
sl@0: /**
sl@0:  * \brief Compare tribools for inequality
sl@0:  *
sl@0:  * \returns the result of comparing two tribool values for inequality,
sl@0:  * according to the following table:
sl@0:  *       <table border=1>
sl@0:  *           <tr>
sl@0:  *             <th><center><code>!=</code></center></th>
sl@0:  *             <th><center>false</center></th>
sl@0:  *             <th><center>true</center></th>
sl@0:  *             <th><center>indeterminate</center></th>
sl@0:  *           </tr>
sl@0:  *           <tr>
sl@0:  *             <th><center>false</center></th>
sl@0:  *             <td><center>false</center></td>
sl@0:  *             <td><center>true</center></td>
sl@0:  *             <td><center>indeterminate</center></td>
sl@0:  *           </tr>
sl@0:  *           <tr>
sl@0:  *             <th><center>true</center></th>
sl@0:  *             <td><center>true</center></td>
sl@0:  *             <td><center>false</center></td>
sl@0:  *             <td><center>indeterminate</center></td>
sl@0:  *           </tr>
sl@0:  *           <tr>
sl@0:  *             <th><center>indeterminate</center></th>
sl@0:  *             <td><center>indeterminate</center></td>
sl@0:  *             <td><center>indeterminate</center></td>
sl@0:  *             <td><center>indeterminate</center></td>
sl@0:  *           </tr>
sl@0:  *       </table>
sl@0:  * \throws nothrow
sl@0:  */
sl@0: inline tribool operator!=(tribool x, tribool y)
sl@0: {
sl@0:   if (indeterminate(x) || indeterminate(y))
sl@0:     return indeterminate;
sl@0:   else
sl@0:     return !(x && y || !x && !y);
sl@0: }
sl@0: 
sl@0: /**
sl@0:  * \overload
sl@0:  */
sl@0: inline tribool operator!=(tribool x, bool y) { return x != tribool(y); }
sl@0: 
sl@0: /**
sl@0:  * \overload
sl@0:  */
sl@0: inline tribool operator!=(bool x, tribool y) { return tribool(x) != y; }
sl@0: 
sl@0: /**
sl@0:  * \overload
sl@0:  */
sl@0: inline tribool operator!=(indeterminate_keyword_t, tribool x)
sl@0: { return tribool(indeterminate) != x; }
sl@0: 
sl@0: /**
sl@0:  * \overload
sl@0:  */
sl@0: inline tribool operator!=(tribool x, indeterminate_keyword_t)
sl@0: { return x != tribool(indeterminate); }
sl@0: 
sl@0: } } // end namespace boost::logic
sl@0: 
sl@0: // Pull tribool and indeterminate into namespace "boost"
sl@0: namespace boost {
sl@0:   using logic::tribool;
sl@0:   using logic::indeterminate;
sl@0: }
sl@0: 
sl@0: /**
sl@0:  * \brief Declare a new name for the third state of a tribool
sl@0:  *
sl@0:  * Use this macro to declare a new name for the third state of a
sl@0:  * tribool. This state can have any number of new names (in addition
sl@0:  * to \c indeterminate), all of which will be equivalent. The new name will be
sl@0:  * placed in the namespace in which the macro is expanded.
sl@0:  *
sl@0:  * Example:
sl@0:  *   BOOST_TRIBOOL_THIRD_STATE(true_or_false)
sl@0:  *
sl@0:  *   tribool x(true_or_false);
sl@0:  *   // potentially set x
sl@0:  *   if (true_or_false(x)) {
sl@0:  *     // don't know what x is
sl@0:  *   }
sl@0:  */
sl@0: #define BOOST_TRIBOOL_THIRD_STATE(Name)                                 \
sl@0: inline bool                                                             \
sl@0: Name(boost::logic::tribool x,                                           \
sl@0:      boost::logic::detail::indeterminate_t dummy =                      \
sl@0:        boost::logic::detail::indeterminate_t())                         \
sl@0: { return x.value == boost::logic::tribool::indeterminate_value; }
sl@0: 
sl@0: #endif // BOOST_LOGIC_TRIBOOL_HPP
sl@0: