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