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// Three-state boolean logic library
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// Copyright Douglas Gregor 2002-2004. Use, modification and
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// distribution is subject to the Boost Software License, Version
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// 1.0. (See accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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// For more information, see http://www.boost.org
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#ifndef BOOST_LOGIC_TRIBOOL_HPP
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#define BOOST_LOGIC_TRIBOOL_HPP
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#include <boost/logic/tribool_fwd.hpp>
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#include <boost/config.hpp>
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#include <boost/detail/workaround.hpp>
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#if BOOST_WORKAROUND(_MSC_VER, >= 1200)
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# pragma once
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#endif
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namespace boost { namespace logic {
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/// INTERNAL ONLY
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namespace detail {
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/**
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* INTERNAL ONLY
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*
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* \brief A type used only to uniquely identify the 'indeterminate'
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* function/keyword.
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*/
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struct indeterminate_t
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{
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#if BOOST_WORKAROUND(__BORLANDC__, < 0x0600)
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char dummy_; // BCB would use 8 bytes by default
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#endif
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};
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} // end namespace detail
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/**
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* INTERNAL ONLY
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* The type of the 'indeterminate' keyword. This has the same type as the
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* function 'indeterminate' so that we can recognize when the keyword is
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* used.
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*/
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typedef bool (*indeterminate_keyword_t)(tribool, detail::indeterminate_t);
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/**
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* \brief Keyword and test function for the indeterminate tribool value
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*
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* The \c indeterminate function has a dual role. It's first role is
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* as a unary function that tells whether the tribool value is in the
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* "indeterminate" state. It's second role is as a keyword
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* representing the indeterminate (just like "true" and "false"
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* represent the true and false states). If you do not like the name
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* "indeterminate", and would prefer to use a different name, see the
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* macro \c BOOST_TRIBOOL_THIRD_STATE.
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*
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* \returns <tt>x.value == tribool::indeterminate_value</tt>
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* \throws nothrow
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*/
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inline bool
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indeterminate(tribool x,
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detail::indeterminate_t dummy = detail::indeterminate_t());
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/**
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* \brief A 3-state boolean type.
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*
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* 3-state boolean values are either true, false, or
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* indeterminate.
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*/
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class tribool
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{
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private:
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/// INTERNAL ONLY
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struct dummy {
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void nonnull() {};
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};
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typedef void (dummy::*safe_bool)();
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public:
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/**
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* Construct a new 3-state boolean value with the value 'false'.
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*
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* \throws nothrow
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*/
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tribool() : value(false_value) {}
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/**
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* Construct a new 3-state boolean value with the given boolean
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* value, which may be \c true or \c false.
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*
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* \throws nothrow
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*/
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tribool(bool value) : value(value? true_value : false_value) {}
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/**
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* Construct a new 3-state boolean value with an indeterminate value.
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*
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* \throws nothrow
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*/
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tribool(indeterminate_keyword_t) : value(indeterminate_value) {}
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/**
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* Use a 3-state boolean in a boolean context. Will evaluate true in a
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* boolean context only when the 3-state boolean is definitely true.
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*
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* \returns true if the 3-state boolean is true, false otherwise
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* \throws nothrow
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*/
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operator safe_bool() const
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{
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return value == true_value? &dummy::nonnull : 0;
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}
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/**
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* The actual stored value in this 3-state boolean, which may be false, true,
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* or indeterminate.
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*/
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enum value_t { false_value, true_value, indeterminate_value } value;
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};
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// Check if the given tribool has an indeterminate value. Also doubles as a
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// keyword for the 'indeterminate' value
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inline bool indeterminate(tribool x, detail::indeterminate_t)
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{
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return x.value == tribool::indeterminate_value;
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}
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/** @defgroup logical Logical operations
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*/
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//@{
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/**
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* \brief Computes the logical negation of a tribool
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*
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* \returns the logical negation of the tribool, according to the
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* table:
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* <table border=1>
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* <tr>
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* <th><center><code>!</code></center></th>
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* <th/>
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* </tr>
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* <tr>
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* <th><center>false</center></th>
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* <td><center>true</center></td>
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* </tr>
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* <tr>
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* <th><center>true</center></th>
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* <td><center>false</center></td>
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* </tr>
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* <tr>
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* <th><center>indeterminate</center></th>
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* <td><center>indeterminate</center></td>
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* </tr>
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* </table>
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* \throws nothrow
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*/
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inline tribool operator!(tribool x)
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{
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return x.value == tribool::false_value? tribool(true)
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:x.value == tribool::true_value? tribool(false)
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:tribool(indeterminate);
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}
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/**
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* \brief Computes the logical conjuction of two tribools
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*
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* \returns the result of logically ANDing the two tribool values,
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* according to the following table:
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* <table border=1>
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* <tr>
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* <th><center><code>&&</code></center></th>
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* <th><center>false</center></th>
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* <th><center>true</center></th>
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* <th><center>indeterminate</center></th>
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* </tr>
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* <tr>
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* <th><center>false</center></th>
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* <td><center>false</center></td>
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* <td><center>false</center></td>
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* <td><center>false</center></td>
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* </tr>
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* <tr>
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* <th><center>true</center></th>
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* <td><center>false</center></td>
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* <td><center>true</center></td>
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* <td><center>indeterminate</center></td>
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* </tr>
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* <tr>
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* <th><center>indeterminate</center></th>
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* <td><center>false</center></td>
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* <td><center>indeterminate</center></td>
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* <td><center>indeterminate</center></td>
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* </tr>
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* </table>
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* \throws nothrow
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*/
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inline tribool operator&&(tribool x, tribool y)
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{
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if (static_cast<bool>(!x) || static_cast<bool>(!y))
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return false;
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else if (static_cast<bool>(x) && static_cast<bool>(y))
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return true;
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else
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return indeterminate;
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}
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/**
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* \overload
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*/
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inline tribool operator&&(tribool x, bool y)
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{ return y? x : tribool(false); }
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/**
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* \overload
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*/
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inline tribool operator&&(bool x, tribool y)
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{ return x? y : tribool(false); }
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/**
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* \overload
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*/
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inline tribool operator&&(indeterminate_keyword_t, tribool x)
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{ return !x? tribool(false) : tribool(indeterminate); }
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/**
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* \overload
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*/
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inline tribool operator&&(tribool x, indeterminate_keyword_t)
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{ return !x? tribool(false) : tribool(indeterminate); }
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/**
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* \brief Computes the logical disjunction of two tribools
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*
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* \returns the result of logically ORing the two tribool values,
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* according to the following table:
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* <table border=1>
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* <tr>
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* <th><center><code>||</code></center></th>
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* <th><center>false</center></th>
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* <th><center>true</center></th>
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* <th><center>indeterminate</center></th>
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* </tr>
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* <tr>
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* <th><center>false</center></th>
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* <td><center>false</center></td>
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* <td><center>true</center></td>
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* <td><center>indeterminate</center></td>
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* </tr>
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* <tr>
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* <th><center>true</center></th>
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* <td><center>true</center></td>
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* <td><center>true</center></td>
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* <td><center>true</center></td>
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* </tr>
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* <tr>
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* <th><center>indeterminate</center></th>
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* <td><center>indeterminate</center></td>
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* <td><center>true</center></td>
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* <td><center>indeterminate</center></td>
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* </tr>
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* </table>
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* \throws nothrow
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*/
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inline tribool operator||(tribool x, tribool y)
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{
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if (static_cast<bool>(!x) && static_cast<bool>(!y))
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return false;
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else if (static_cast<bool>(x) || static_cast<bool>(y))
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return true;
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else
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return indeterminate;
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}
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/**
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* \overload
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*/
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inline tribool operator||(tribool x, bool y)
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{ return y? tribool(true) : x; }
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/**
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* \overload
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*/
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inline tribool operator||(bool x, tribool y)
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{ return x? tribool(true) : y; }
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/**
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* \overload
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*/
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inline tribool operator||(indeterminate_keyword_t, tribool x)
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{ return x? tribool(true) : tribool(indeterminate); }
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/**
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* \overload
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*/
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inline tribool operator||(tribool x, indeterminate_keyword_t)
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{ return x? tribool(true) : tribool(indeterminate); }
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//@}
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/**
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* \brief Compare tribools for equality
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*
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* \returns the result of comparing two tribool values, according to
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* the following table:
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* <table border=1>
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307 |
* <tr>
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* <th><center><code>==</code></center></th>
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309 |
* <th><center>false</center></th>
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310 |
* <th><center>true</center></th>
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311 |
* <th><center>indeterminate</center></th>
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312 |
* </tr>
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313 |
* <tr>
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314 |
* <th><center>false</center></th>
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315 |
* <td><center>true</center></td>
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316 |
* <td><center>false</center></td>
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317 |
* <td><center>indeterminate</center></td>
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318 |
* </tr>
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319 |
* <tr>
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* <th><center>true</center></th>
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321 |
* <td><center>false</center></td>
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322 |
* <td><center>true</center></td>
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323 |
* <td><center>indeterminate</center></td>
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324 |
* </tr>
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325 |
* <tr>
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* <th><center>indeterminate</center></th>
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* <td><center>indeterminate</center></td>
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* <td><center>indeterminate</center></td>
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329 |
* <td><center>indeterminate</center></td>
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330 |
* </tr>
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* </table>
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* \throws nothrow
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|
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*/
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|
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inline tribool operator==(tribool x, tribool y)
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|
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{
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if (indeterminate(x) || indeterminate(y))
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|
337 |
return indeterminate;
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|
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else
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|
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return x && y || !x && !y;
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|
340 |
}
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|
341 |
|
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|
342 |
/**
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sl@0
|
343 |
* \overload
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|
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|
344 |
*/
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sl@0
|
345 |
inline tribool operator==(tribool x, bool y) { return x == tribool(y); }
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|
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|
346 |
|
|
sl@0
|
347 |
/**
|
|
sl@0
|
348 |
* \overload
|
|
sl@0
|
349 |
*/
|
|
sl@0
|
350 |
inline tribool operator==(bool x, tribool y) { return tribool(x) == y; }
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|
sl@0
|
351 |
|
|
sl@0
|
352 |
/**
|
|
sl@0
|
353 |
* \overload
|
|
sl@0
|
354 |
*/
|
|
sl@0
|
355 |
inline tribool operator==(indeterminate_keyword_t, tribool x)
|
|
sl@0
|
356 |
{ return tribool(indeterminate) == x; }
|
|
sl@0
|
357 |
|
|
sl@0
|
358 |
/**
|
|
sl@0
|
359 |
* \overload
|
|
sl@0
|
360 |
*/
|
|
sl@0
|
361 |
inline tribool operator==(tribool x, indeterminate_keyword_t)
|
|
sl@0
|
362 |
{ return tribool(indeterminate) == x; }
|
|
sl@0
|
363 |
|
|
sl@0
|
364 |
/**
|
|
sl@0
|
365 |
* \brief Compare tribools for inequality
|
|
sl@0
|
366 |
*
|
|
sl@0
|
367 |
* \returns the result of comparing two tribool values for inequality,
|
|
sl@0
|
368 |
* according to the following table:
|
|
sl@0
|
369 |
* <table border=1>
|
|
sl@0
|
370 |
* <tr>
|
|
sl@0
|
371 |
* <th><center><code>!=</code></center></th>
|
|
sl@0
|
372 |
* <th><center>false</center></th>
|
|
sl@0
|
373 |
* <th><center>true</center></th>
|
|
sl@0
|
374 |
* <th><center>indeterminate</center></th>
|
|
sl@0
|
375 |
* </tr>
|
|
sl@0
|
376 |
* <tr>
|
|
sl@0
|
377 |
* <th><center>false</center></th>
|
|
sl@0
|
378 |
* <td><center>false</center></td>
|
|
sl@0
|
379 |
* <td><center>true</center></td>
|
|
sl@0
|
380 |
* <td><center>indeterminate</center></td>
|
|
sl@0
|
381 |
* </tr>
|
|
sl@0
|
382 |
* <tr>
|
|
sl@0
|
383 |
* <th><center>true</center></th>
|
|
sl@0
|
384 |
* <td><center>true</center></td>
|
|
sl@0
|
385 |
* <td><center>false</center></td>
|
|
sl@0
|
386 |
* <td><center>indeterminate</center></td>
|
|
sl@0
|
387 |
* </tr>
|
|
sl@0
|
388 |
* <tr>
|
|
sl@0
|
389 |
* <th><center>indeterminate</center></th>
|
|
sl@0
|
390 |
* <td><center>indeterminate</center></td>
|
|
sl@0
|
391 |
* <td><center>indeterminate</center></td>
|
|
sl@0
|
392 |
* <td><center>indeterminate</center></td>
|
|
sl@0
|
393 |
* </tr>
|
|
sl@0
|
394 |
* </table>
|
|
sl@0
|
395 |
* \throws nothrow
|
|
sl@0
|
396 |
*/
|
|
sl@0
|
397 |
inline tribool operator!=(tribool x, tribool y)
|
|
sl@0
|
398 |
{
|
|
sl@0
|
399 |
if (indeterminate(x) || indeterminate(y))
|
|
sl@0
|
400 |
return indeterminate;
|
|
sl@0
|
401 |
else
|
|
sl@0
|
402 |
return !(x && y || !x && !y);
|
|
sl@0
|
403 |
}
|
|
sl@0
|
404 |
|
|
sl@0
|
405 |
/**
|
|
sl@0
|
406 |
* \overload
|
|
sl@0
|
407 |
*/
|
|
sl@0
|
408 |
inline tribool operator!=(tribool x, bool y) { return x != tribool(y); }
|
|
sl@0
|
409 |
|
|
sl@0
|
410 |
/**
|
|
sl@0
|
411 |
* \overload
|
|
sl@0
|
412 |
*/
|
|
sl@0
|
413 |
inline tribool operator!=(bool x, tribool y) { return tribool(x) != y; }
|
|
sl@0
|
414 |
|
|
sl@0
|
415 |
/**
|
|
sl@0
|
416 |
* \overload
|
|
sl@0
|
417 |
*/
|
|
sl@0
|
418 |
inline tribool operator!=(indeterminate_keyword_t, tribool x)
|
|
sl@0
|
419 |
{ return tribool(indeterminate) != x; }
|
|
sl@0
|
420 |
|
|
sl@0
|
421 |
/**
|
|
sl@0
|
422 |
* \overload
|
|
sl@0
|
423 |
*/
|
|
sl@0
|
424 |
inline tribool operator!=(tribool x, indeterminate_keyword_t)
|
|
sl@0
|
425 |
{ return x != tribool(indeterminate); }
|
|
sl@0
|
426 |
|
|
sl@0
|
427 |
} } // end namespace boost::logic
|
|
sl@0
|
428 |
|
|
sl@0
|
429 |
// Pull tribool and indeterminate into namespace "boost"
|
|
sl@0
|
430 |
namespace boost {
|
|
sl@0
|
431 |
using logic::tribool;
|
|
sl@0
|
432 |
using logic::indeterminate;
|
|
sl@0
|
433 |
}
|
|
sl@0
|
434 |
|
|
sl@0
|
435 |
/**
|
|
sl@0
|
436 |
* \brief Declare a new name for the third state of a tribool
|
|
sl@0
|
437 |
*
|
|
sl@0
|
438 |
* Use this macro to declare a new name for the third state of a
|
|
sl@0
|
439 |
* tribool. This state can have any number of new names (in addition
|
|
sl@0
|
440 |
* to \c indeterminate), all of which will be equivalent. The new name will be
|
|
sl@0
|
441 |
* placed in the namespace in which the macro is expanded.
|
|
sl@0
|
442 |
*
|
|
sl@0
|
443 |
* Example:
|
|
sl@0
|
444 |
* BOOST_TRIBOOL_THIRD_STATE(true_or_false)
|
|
sl@0
|
445 |
*
|
|
sl@0
|
446 |
* tribool x(true_or_false);
|
|
sl@0
|
447 |
* // potentially set x
|
|
sl@0
|
448 |
* if (true_or_false(x)) {
|
|
sl@0
|
449 |
* // don't know what x is
|
|
sl@0
|
450 |
* }
|
|
sl@0
|
451 |
*/
|
|
sl@0
|
452 |
#define BOOST_TRIBOOL_THIRD_STATE(Name) \
|
|
sl@0
|
453 |
inline bool \
|
|
sl@0
|
454 |
Name(boost::logic::tribool x, \
|
|
sl@0
|
455 |
boost::logic::detail::indeterminate_t dummy = \
|
|
sl@0
|
456 |
boost::logic::detail::indeterminate_t()) \
|
|
sl@0
|
457 |
{ return x.value == boost::logic::tribool::indeterminate_value; }
|
|
sl@0
|
458 |
|
|
sl@0
|
459 |
#endif // BOOST_LOGIC_TRIBOOL_HPP
|
|
sl@0
|
460 |
|