344 lines
11 KiB
C++
344 lines
11 KiB
C++
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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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#ifndef BOOST_LOGIC_TRIBOOL_IO_HPP
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#define BOOST_LOGIC_TRIBOOL_IO_HPP
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#include <boost/logic/tribool.hpp>
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#include <boost/detail/workaround.hpp>
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#include <boost/noncopyable.hpp>
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#if defined(_MSC_VER)
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# pragma once
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#endif
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#ifndef BOOST_NO_STD_LOCALE
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# include <locale>
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#endif
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#include <string>
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#include <iostream>
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namespace boost { namespace logic {
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#ifdef BOOST_NO_STD_LOCALE
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/**
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* \brief Returns a string containing the default name for the \c
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* false value of a tribool with the given character type T.
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*
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* This function only exists when the C++ standard library
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* implementation does not support locales.
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*/
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template<typename T> std::basic_string<T> default_false_name();
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/**
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* \brief Returns the character string "false".
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*
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* This function only exists when the C++ standard library
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* implementation does not support locales.
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*/
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template<>
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inline std::basic_string<char> default_false_name<char>()
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{ return "false"; }
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# ifndef BOOST_NO_WCHAR_T
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/**
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* \brief Returns the wide character string L"false".
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*
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* This function only exists when the C++ standard library
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* implementation does not support locales.
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*/
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template<>
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inline std::basic_string<wchar_t> default_false_name<wchar_t>()
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{ return L"false"; }
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# endif
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/**
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* \brief Returns a string containing the default name for the \c true
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* value of a tribool with the given character type T.
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*
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* This function only exists when the C++ standard library
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* implementation does not support locales.
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*/
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template<typename T> std::basic_string<T> default_true_name();
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/**
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* \brief Returns the character string "true".
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*
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* This function only exists when the C++ standard library
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* implementation does not support locales.
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*/
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template<>
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inline std::basic_string<char> default_true_name<char>()
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{ return "true"; }
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# ifndef BOOST_NO_WCHAR_T
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/**
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* \brief Returns the wide character string L"true".
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*
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* This function only exists * when the C++ standard library
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* implementation does not support * locales.
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*/
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template<>
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inline std::basic_string<wchar_t> default_true_name<wchar_t>()
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{ return L"true"; }
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# endif
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#endif
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/**
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* \brief Returns a string containing the default name for the indeterminate
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* value of a tribool with the given character type T.
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*
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* This routine is used by the input and output streaming operators
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* for tribool when there is no locale support or the stream's locale
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* does not contain the indeterminate_name facet.
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*/
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template<typename T> std::basic_string<T> get_default_indeterminate_name();
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/// Returns the character string "indeterminate".
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template<>
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inline std::basic_string<char> get_default_indeterminate_name<char>()
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{ return "indeterminate"; }
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#ifndef BOOST_NO_WCHAR_T
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/// Returns the wide character string L"indeterminate".
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template<>
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inline std::basic_string<wchar_t> get_default_indeterminate_name<wchar_t>()
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{ return L"indeterminate"; }
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#endif
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// http://www.cantrip.org/locale.html
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#ifndef BOOST_NO_STD_LOCALE
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/**
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* \brief A locale facet specifying the name of the indeterminate
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* value of a tribool.
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*
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* The facet is used to perform I/O on tribool values when \c
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* std::boolalpha has been specified. This class template is only
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* available if the C++ standard library implementation supports
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* locales.
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*/
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template<typename CharT>
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class indeterminate_name : public std::locale::facet, private boost::noncopyable
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{
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public:
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typedef CharT char_type;
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typedef std::basic_string<CharT> string_type;
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/// Construct the facet with the default name
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indeterminate_name() : name_(get_default_indeterminate_name<CharT>()) {}
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/// Construct the facet with the given name for the indeterminate value
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explicit indeterminate_name(const string_type& initial_name)
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: name_(initial_name) {}
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/// Returns the name for the indeterminate value
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string_type name() const { return name_; }
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/// Uniquily identifies this facet with the locale.
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static std::locale::id id;
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private:
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string_type name_;
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};
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template<typename CharT> std::locale::id indeterminate_name<CharT>::id;
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#endif
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/**
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* \brief Writes the value of a tribool to a stream.
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*
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* When the value of @p x is either \c true or \c false, this routine
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* is semantically equivalent to:
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* \code out << static_cast<bool>(x); \endcode
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*
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* When @p x has an indeterminate value, it outputs either the integer
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* value 2 (if <tt>(out.flags() & std::ios_base::boolalpha) == 0</tt>)
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* or the name of the indeterminate value. The name of the
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* indeterminate value comes from the indeterminate_name facet (if it
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* is defined in the output stream's locale), or from the
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* get_default_indeterminate_name function (if it is not defined in the
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* locale or if the C++ standard library implementation does not
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* support locales).
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*
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* \returns @p out
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*/
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template<typename CharT, typename Traits>
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inline std::basic_ostream<CharT, Traits>&
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operator<<(std::basic_ostream<CharT, Traits>& out, tribool x)
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{
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if (!indeterminate(x)) {
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out << static_cast<bool>(x);
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} else {
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typename std::basic_ostream<CharT, Traits>::sentry cerberus(out);
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if (cerberus) {
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if (out.flags() & std::ios_base::boolalpha) {
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#ifndef BOOST_NO_STD_LOCALE
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if (BOOST_HAS_FACET(indeterminate_name<CharT>, out.getloc())) {
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const indeterminate_name<CharT>& facet =
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BOOST_USE_FACET(indeterminate_name<CharT>, out.getloc());
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out << facet.name();
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} else {
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out << get_default_indeterminate_name<CharT>();
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}
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#else
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out << get_default_indeterminate_name<CharT>();
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#endif
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}
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else
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out << 2;
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}
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}
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return out;
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}
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/**
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* \brief Writes the indeterminate tribool value to a stream.
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*
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* This routine outputs either the integer
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* value 2 (if <tt>(out.flags() & std::ios_base::boolalpha) == 0</tt>)
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* or the name of the indeterminate value. The name of the
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* indeterminate value comes from the indeterminate_name facet (if it
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* is defined in the output stream's locale), or from the
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* get_default_indeterminate_name function (if it is not defined in the
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* locale or if the C++ standard library implementation does not
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* support locales).
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*
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* \returns @p out
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*/
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template<typename CharT, typename Traits>
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inline std::basic_ostream<CharT, Traits>&
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operator<<(std::basic_ostream<CharT, Traits>& out,
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bool (*)(tribool, detail::indeterminate_t))
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{ return out << tribool(indeterminate); }
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/**
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* \brief Reads a tribool value from a stream.
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*
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* When <tt>(out.flags() & std::ios_base::boolalpha) == 0</tt>, this
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* function reads a \c long value from the input stream @p in and
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* converts that value to a tribool. If that value is 0, @p x becomes
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* \c false; if it is 1, @p x becomes \c true; if it is 2, @p becomes
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* \c indetermine; otherwise, the operation fails (and the fail bit is
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* set on the input stream @p in).
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*
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* When <tt>(out.flags() & std::ios_base::boolalpha) != 0</tt>, this
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* function first determines the names of the false, true, and
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* indeterminate values. The false and true names are extracted from
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* the \c std::numpunct facet of the input stream's locale (if the C++
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* standard library implementation supports locales), or from the \c
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* default_false_name and \c default_true_name functions (if there is
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* no locale support). The indeterminate name is extracted from the
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* appropriate \c indeterminate_name facet (if it is available in the
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* input stream's locale), or from the \c get_default_indeterminate_name
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* function (if the C++ standard library implementation does not
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* support locales, or the \c indeterminate_name facet is not
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* specified for this locale object). The input is then matched to
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* each of these names, and the tribool @p x is assigned the value
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* corresponding to the longest name that matched. If no name is
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* matched or all names are empty, the operation fails (and the fail
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* bit is set on the input stream @p in).
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*
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* \returns @p in
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*/
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template<typename CharT, typename Traits>
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inline std::basic_istream<CharT, Traits>&
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operator>>(std::basic_istream<CharT, Traits>& in, tribool& x)
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{
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if (in.flags() & std::ios_base::boolalpha) {
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typename std::basic_istream<CharT, Traits>::sentry cerberus(in);
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if (cerberus) {
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typedef std::basic_string<CharT> string_type;
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#ifndef BOOST_NO_STD_LOCALE
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const std::numpunct<CharT>& numpunct_facet =
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BOOST_USE_FACET(std::numpunct<CharT>, in.getloc());
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string_type falsename = numpunct_facet.falsename();
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string_type truename = numpunct_facet.truename();
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string_type othername;
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if (BOOST_HAS_FACET(indeterminate_name<CharT>, in.getloc())) {
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othername =
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BOOST_USE_FACET(indeterminate_name<CharT>, in.getloc()).name();
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} else {
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othername = get_default_indeterminate_name<CharT>();
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}
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#else
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string_type falsename = default_false_name<CharT>();
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string_type truename = default_true_name<CharT>();
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string_type othername = get_default_indeterminate_name<CharT>();
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#endif
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typename string_type::size_type pos = 0;
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bool falsename_ok = true, truename_ok = true, othername_ok = true;
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// Modeled after the code from Library DR 17
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while ((falsename_ok && pos < falsename.size())
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|| (othername_ok && pos < othername.size())) {
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typename Traits::int_type c = in.get();
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if (c == Traits::eof())
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return in;
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bool matched = false;
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if (falsename_ok && pos < falsename.size()) {
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if (Traits::eq(Traits::to_char_type(c), falsename[pos]))
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matched = true;
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else
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falsename_ok = false;
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}
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if (truename_ok && pos < truename.size()) {
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if (Traits::eq(Traits::to_char_type(c), truename[pos]))
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matched = true;
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else
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truename_ok = false;
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}
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if (othername_ok && pos < othername.size()) {
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if (Traits::eq(Traits::to_char_type(c), othername[pos]))
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matched = true;
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else
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othername_ok = false;
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}
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if (matched) { ++pos; }
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if (pos > falsename.size()) falsename_ok = false;
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if (pos > truename.size()) truename_ok = false;
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if (pos > othername.size()) othername_ok = false;
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}
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if (pos == 0)
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in.setstate(std::ios_base::failbit);
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else {
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if (falsename_ok) x = false;
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else if (truename_ok) x = true;
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else if (othername_ok) x = indeterminate;
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else in.setstate(std::ios_base::failbit);
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}
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}
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} else {
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long value;
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if (in >> value) {
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switch (value) {
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case 0: x = false; break;
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case 1: x = true; break;
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case 2: x = indeterminate; break;
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default: in.setstate(std::ios_base::failbit); break;
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}
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}
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}
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return in;
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}
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} } // end namespace boost::logic
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#endif // BOOST_LOGIC_TRIBOOL_IO_HPP
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