| // 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 |
| |