code:
//  return_type_traits.hpp -- Boost Lambda Library ---------------------------

// Copyright (C) 1999, 2000 Jaakko Jarvi (jaakko.jarvi@cs.utu.fi)
//
// Distributed under 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 www.boost.org

#ifndef BOOST_LAMBDA_RETURN_TYPE_TRAITS_HPP
#define BOOST_LAMBDA_RETURN_TYPE_TRAITS_HPP

#include "boost/mpl/has_xxx.hpp"

#include <cstddef> // needed for the ptrdiff_t

namespace boost {
namespace lambda {

// Much of the type deduction code for standard arithmetic types
// from Gary Powell

  // different arities:
template <class Act, class A1> struct return_type_1; // 1-ary actions
template <class Act, class A1, class A2> struct return_type_2; // 2-ary
template <class Act, class Args> struct return_type_N; // >3- ary

template <class Act, class A1> struct return_type_1_prot;
template <class Act, class A1, class A2> struct return_type_2_prot; // 2-ary
template <class Act, class A1> struct return_type_N_prot; // >3-ary

namespace detail {

template<class> class return_type_deduction_failure {};

  // In some cases return type deduction should fail (an invalid lambda
  // expression). Sometimes the lambda expression can be ok, the return type
  // just is not deducible (user defined operators). Then return type deduction
  // should never be entered at all, and the use of ret<> does this.
  // However, for nullary lambda functors, return type deduction is always
  // entered, and there seems to be no way around this.

  // (the return type is part of the prototype of the non-template
  // operator()(). The prototype is instantiated, even though the body
  // is not.)

  // So, in the case the return type deduction should fail, it should not
  // fail directly, but rather result in a valid but wrong return type,
  // causing a compile time error only if the function is really called.

} // end detail

// return_type_X_prot classes --------------------------------------------
// These classes are the first layer that gets instantiated from the
// lambda_functor_base sig templates. It will check whether
// the action is protectable and one of arguments is "protected" or its
// evaluation will otherwise result in another lambda functor.
// If this is a case, the result type will be another lambda functor.

// The arguments are always non-reference types, except for comma action
// where the right argument can be a reference too. This is because it
// matters (in the builtin case) whether the argument is an lvalue or
// rvalue: int i; i, 1 -> rvalue; 1, i -> lvalue

template <class Act, class A> struct return_type_1_prot {
public:
  typedef typename
    detail::IF<
      is_protectable<Act>::value && is_lambda_functor<A>::value,
      lambda_functor<
        lambda_functor_base<
          Act,
          tuple<typename detail::remove_reference_and_cv<A>::type>
        >
      >,
      typename return_type_1<Act, A>::type
    >::RET type;
};

  // take care of the unavoidable instantiation for nullary case
template<class Act> struct return_type_1_prot<Act, null_type> {
  typedef null_type type;
};

// Unary actions (result from unary operators)
// do not have a default return type.
template<class Act, class A> struct return_type_1 {
   typedef typename
     detail::return_type_deduction_failure<return_type_1> type;
};

namespace detail {

  template <class T>
  class protect_conversion {
      typedef typename boost::remove_reference<T>::type non_ref_T;
    public:

  // add const to rvalues, so that all rvalues are stored as const in
  // the args tuple
    typedef typename detail::IF_type<
      boost::is_reference<T>::value && !boost::is_const<non_ref_T>::value,
      detail::identity_mapping<T>,
      const_copy_argument<non_ref_T> // handles funtion and array
    >::type type;                      // types correctly
  };

} // end detail

template <class Act, class A, class B> struct return_type_2_prot {

// experimental feature
  // We may have a lambda functor as a result type of a subexpression
  // (if protect) has  been used.
  // Thus, if one of the parameter types is a lambda functor, the result
  // is a lambda functor as well.
  // We need to make a conservative choise here.
  // The resulting lambda functor stores all const reference arguments as
  // const copies. References to non-const are stored as such.
  // So if the source of the argument is a const open argument, a bound
  // argument stored as a const reference, or a function returning a
  // const reference, that information is lost. There is no way of
  // telling apart 'real const references' from just 'LL internal
  // const references' (or it would be really hard)

  // The return type is a subclass of lambda_functor, which has a converting
  // copy constructor. It can copy any lambda functor, that has the same
  // action type and code, and a copy compatible argument tuple.

  typedef typename boost::remove_reference<A>::type non_ref_A;
  typedef typename boost::remove_reference<B>::type non_ref_B;

typedef typename
  detail::IF<
    is_protectable<Act>::value &&
      (is_lambda_functor<A>::value || is_lambda_functor<B>::value),
    lambda_functor<
      lambda_functor_base<
        Act,
        tuple<typename detail::protect_conversion<A>::type,
              typename detail::protect_conversion<B>::type>
      >
    >,
    typename return_type_2<Act, non_ref_A, non_ref_B>::type
  >::RET type;
};

  // take care of the unavoidable instantiation for nullary case
template<class Act> struct return_type_2_prot<Act, null_type, null_type> {
  typedef null_type type;
};
  // take care of the unavoidable instantiation for nullary case
template<class Act, class Other> struct return_type_2_prot<Act, Other, null_type> {
  typedef null_type type;
};
  // take care of the unavoidable instantiation for nullary case
template<class Act, class Other> struct return_type_2_prot<Act, null_type, Other> {
  typedef null_type type;
};

  // comma is a special case, as the user defined operator can return
  // an lvalue (reference) too, hence it must be handled at this level.
template<class A, class B>
struct return_type_2_comma
{
  typedef typename boost::remove_reference<A>::type non_ref_A;
  typedef typename boost::remove_reference<B>::type non_ref_B;

typedef typename
  detail::IF<
    is_protectable<other_action<comma_action> >::value && // it is protectable
    (is_lambda_functor<A>::value || is_lambda_functor<B>::value),
    lambda_functor<
      lambda_functor_base<
        other_action<comma_action>,
        tuple<typename detail::protect_conversion<A>::type,
              typename detail::protect_conversion<B>::type>
      >
    >,
    typename
      return_type_2<other_action<comma_action>, non_ref_A, non_ref_B>::type
  >::RET type1;

   // if no user defined return_type_2 (or plain_return_type_2) specialization
  // matches, then return the righthand argument
  typedef typename
    detail::IF<
      boost::is_same<type1, detail::unspecified>::value,
      B,
      type1
    >::RET type;

};

  // currently there are no protectable actions with > 2 args

template<class Act, class Args> struct return_type_N_prot {
  typedef typename return_type_N<Act, Args>::type type;
};

  // take care of the unavoidable instantiation for nullary case
template<class Act> struct return_type_N_prot<Act, null_type> {
  typedef null_type type;
};

// handle different kind of actions ------------------------

  // use the return type given in the bind invocation as bind<Ret>(...)
template<int I, class Args, class Ret>
struct return_type_N<function_action<I, Ret>, Args> {
  typedef Ret type;
};

// ::result_type support

namespace detail
{

BOOST_MPL_HAS_XXX_TRAIT_DEF(result_type)

template<class F> struct get_result_type
{
  typedef typename F::result_type type;
};

template<class F, class A> struct get_sig
{
  typedef typename function_adaptor<F>::template sig<A>::type type;
};

} // namespace detail

  // Ret is detail::unspecified, so try to deduce return type
template<int I, class Args>
struct return_type_N<function_action<I, detail::unspecified>, Args > {

  // in the case of function action, the first element in Args is
  // some type of function
  typedef typename Args::head_type Func;
  typedef typename detail::remove_reference_and_cv<Func>::type plain_Func;

public:
  // pass the function to function_adaptor, and get the return type from
  // that
  typedef typename detail::IF<
    detail::has_result_type<plain_Func>::value,
    detail::get_result_type<plain_Func>,
    detail::get_sig<plain_Func, Args>
  >::RET::type type;
};

} // namespace lambda
} // namespace boost

#endif


code:
// -- select_functions.hpp -- Boost Lambda Library --------------------------

// Copyright (C) 1999, 2000 Jaakko Jarvi (jaakko.jarvi@cs.utu.fi)
//
// Distributed under 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_LAMBDA_SELECT_FUNCTIONS_HPP
#define BOOST_LAMBDA_SELECT_FUNCTIONS_HPP

namespace boost {
namespace lambda {
namespace detail {

// select functions -------------------------------
template<class Any, CALL_TEMPLATE_ARGS>
inline Any& select(Any& any, CALL_FORMAL_ARGS) { CALL_USE_ARGS; return any; }

template<class Arg, CALL_TEMPLATE_ARGS>
inline typename Arg::template sig<tuple<CALL_REFERENCE_TYPES> >::type
select ( const lambda_functor<Arg>& op, CALL_FORMAL_ARGS ) {
  return op.template call<
    typename Arg::template sig<tuple<CALL_REFERENCE_TYPES> >::type
  >(CALL_ACTUAL_ARGS);
}
template<class Arg, CALL_TEMPLATE_ARGS>
inline typename Arg::template sig<tuple<CALL_REFERENCE_TYPES> >::type
select ( lambda_functor<Arg>& op, CALL_FORMAL_ARGS) {
  return op.template call<
    typename Arg::template sig<tuple<CALL_REFERENCE_TYPES> >::type
  >(CALL_ACTUAL_ARGS);
}

// ------------------------------------------------------------------------
// select functions where the return type is explicitly given
// Note: on many functions, this return type is just discarded.
// The select functions are inside a class template, and the return type
// is a class template argument.
// The first implementation used function templates with an explicitly
// specified template parameter.
// However, this resulted in ambiguous calls (at least with gcc 2.95.2
// and edg 2.44). Not sure whether the compilers were right or wrong.

template<class RET> struct r_select {

// Any == RET
  template<class Any, CALL_TEMPLATE_ARGS>
  static
  inline RET go (Any& any, CALL_FORMAL_ARGS) { CALL_USE_ARGS; return any; }

  template<class Arg, CALL_TEMPLATE_ARGS>
  static
  inline RET go (const lambda_functor<Arg>& op, CALL_FORMAL_ARGS ) {
    return op.template call<RET>(CALL_ACTUAL_ARGS);
  }
  template<class Arg, CALL_TEMPLATE_ARGS>
  static
  inline RET go (lambda_functor<Arg>& op, CALL_FORMAL_ARGS ) {
    return op.template call<RET>(CALL_ACTUAL_ARGS);
  }
};

} // namespace detail
} // namespace lambda
} // namespace boost

#endif

license: mit


code:
// -- lambda.hpp -- Boost Lambda Library -----------------------------------
// Copyright (C) 1999, 2000 Jaakko Jarvi (jaakko.jarvi@cs.utu.fi)
//
// Distributed under 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://lambda.cs.utu.fi

#ifndef BOOST_LAMBDA_LAMBDA_HPP
#define BOOST_LAMBDA_LAMBDA_HPP

#include "boost/lambda/core.hpp"

#ifdef BOOST_NO_FDECL_TEMPLATES_AS_TEMPLATE_TEMPLATE_PARAMS
#include <istream>
#include <ostream>
#endif

#include "boost/lambda/detail/operator_actions.hpp"
#include "boost/lambda/detail/operator_lambda_func_base.hpp"
#include "boost/lambda/detail/operator_return_type_traits.hpp"

#include "boost/lambda/detail/operators.hpp"
#include "boost/lambda/detail/member_ptr.hpp"

#endif


code:
// Copyright Kevlin Henney, 2000-2005.
// Copyright Alexander Nasonov, 2006-2010.
// Copyright Antony Polukhin, 2011-2014.
//
// Distributed under 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)
//
// what:  lexical_cast custom keyword cast
// who:   contributed by Kevlin Henney,
//        enhanced with contributions from Terje Slettebo,
//        with additional fixes and suggestions from Gennaro Prota,
//        Beman Dawes, Dave Abrahams, Daryle Walker, Peter Dimov,
//        Alexander Nasonov, Antony Polukhin, Justin Viiret, Michael Hofmann,
//        Cheng Yang, Matthew Bradbury, David W. Birdsall, Pavel Korzh and other Boosters
// when:  November 2000, March 2003, June 2005, June 2006, March 2011 - 2014

#ifndef BOOST_LEXICAL_CAST_INCLUDED
#define BOOST_LEXICAL_CAST_INCLUDED

#include <boost/config.hpp>
#ifdef BOOST_HAS_PRAGMA_ONCE
#   pragma once
#endif

#if defined(BOOST_NO_STRINGSTREAM) || defined(BOOST_NO_STD_WSTRING)
#define BOOST_LCAST_NO_WCHAR_T
#endif

#include <boost/range/iterator_range_core.hpp>
#include <boost/lexical_cast/bad_lexical_cast.hpp>
#include <boost/lexical_cast/try_lexical_convert.hpp>

namespace boost
{
    template <typename Target, typename Source>
    inline Target lexical_cast(const Source &arg)
    {
        Target result = Target();

        if (!boost::conversion::detail::try_lexical_convert(arg, result)) {
            boost::conversion::detail::throw_bad_cast<Source, Target>();
        }

        return result;
    }

    template <typename Target>
    inline Target lexical_cast(const char* chars, std::size_t count)
    {
        return ::boost::lexical_cast<Target>(
            ::boost::iterator_range<const char*>(chars, chars + count)
        );
    }

    template <typename Target>
    inline Target lexical_cast(const unsigned char* chars, std::size_t count)
    {
        return ::boost::lexical_cast<Target>(
            ::boost::iterator_range<const unsigned char*>(chars, chars + count)
        );
    }

    template <typename Target>
    inline Target lexical_cast(const signed char* chars, std::size_t count)
    {
        return ::boost::lexical_cast<Target>(
            ::boost::iterator_range<const signed char*>(chars, chars + count)
        );
    }

#ifndef BOOST_LCAST_NO_WCHAR_T
    template <typename Target>
    inline Target lexical_cast(const wchar_t* chars, std::size_t count)
    {
        return ::boost::lexical_cast<Target>(
            ::boost::iterator_range<const wchar_t*>(chars, chars + count)
        );
    }
#endif
#ifndef BOOST_NO_CXX11_CHAR16_T
    template <typename Target>
    inline Target lexical_cast(const char16_t* chars, std::size_t count)
    {
        return ::boost::lexical_cast<Target>(
            ::boost::iterator_range<const char16_t*>(chars, chars + count)
        );
    }
#endif
#ifndef BOOST_NO_CXX11_CHAR32_T
    template <typename Target>
    inline Target lexical_cast(const char32_t* chars, std::size_t count)
    {
        return ::boost::lexical_cast<Target>(
            ::boost::iterator_range<const char32_t*>(chars, chars + count)
        );
    }
#endif

} // namespace boost

#undef BOOST_LCAST_NO_WCHAR_T

#endif // BOOST_LEXICAL_CAST_INCLUDED


code:
// Copyright Kevlin Henney, 2000-2005.
// Copyright Alexander Nasonov, 2006-2010.
// Copyright Antony Polukhin, 2011-2014.
//
// Distributed under 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)
//
// what:  lexical_cast custom keyword cast
// who:   contributed by Kevlin Henney,
//        enhanced with contributions from Terje Slettebo,
//        with additional fixes and suggestions from Gennaro Prota,
//        Beman Dawes, Dave Abrahams, Daryle Walker, Peter Dimov,
//        Alexander Nasonov, Antony Polukhin, Justin Viiret, Michael Hofmann,
//        Cheng Yang, Matthew Bradbury, David W. Birdsall, Pavel Korzh and other Boosters
// when:  November 2000, March 2003, June 2005, June 2006, March 2011 - 2014

#ifndef BOOST_LEXICAL_CAST_BAD_LEXICAL_CAST_HPP
#define BOOST_LEXICAL_CAST_BAD_LEXICAL_CAST_HPP

#include <boost/config.hpp>
#ifdef BOOST_HAS_PRAGMA_ONCE
#   pragma once
#endif

#include <typeinfo>
#include <exception>
#include <boost/throw_exception.hpp>

namespace boost
{
    // exception used to indicate runtime lexical_cast failure
    class BOOST_SYMBOL_VISIBLE bad_lexical_cast :
    // workaround MSVC bug with std::bad_cast when _HAS_EXCEPTIONS == 0
#if defined(BOOST_MSVC) && defined(_HAS_EXCEPTIONS) && !_HAS_EXCEPTIONS
        public std::exception
#else
        public std::bad_cast
#endif

#if defined(__BORLANDC__) && BOOST_WORKAROUND( __BORLANDC__, < 0x560 )
        // under bcc32 5.5.1 bad_cast doesn't derive from exception
        , public std::exception
#endif

    {
    public:
        bad_lexical_cast() BOOST_NOEXCEPT
#ifndef BOOST_NO_TYPEID
           : source(&typeid(void)), target(&typeid(void))
#endif
        {}

        virtual const char *what() const BOOST_NOEXCEPT_OR_NOTHROW {
            return "bad lexical cast: "
                   "source type value could not be interpreted as target";
        }

        virtual ~bad_lexical_cast() BOOST_NOEXCEPT_OR_NOTHROW
        {}

#ifndef BOOST_NO_TYPEID
        bad_lexical_cast(
                const std::type_info &source_type_arg,
                const std::type_info &target_type_arg) BOOST_NOEXCEPT
            : source(&source_type_arg), target(&target_type_arg)
        {}

        const std::type_info &source_type() const BOOST_NOEXCEPT {
            return *source;
        }

        const std::type_info &target_type() const BOOST_NOEXCEPT {
            return *target;
        }

    private:
        const std::type_info *source;
        const std::type_info *target;
#endif
    };

    namespace conversion { namespace detail {
#ifdef BOOST_NO_TYPEID
        template <class S, class T>
        inline void throw_bad_cast() {
            boost::throw_exception(bad_lexical_cast());
        }
#else
        template <class S, class T>
        inline void throw_bad_cast() {
            boost::throw_exception(bad_lexical_cast(typeid(S), typeid(T)));
        }
#endif
    }} // namespace conversion::detail

} // namespace boost

#endif // BOOST_LEXICAL_CAST_BAD_LEXICAL_CAST_HPP


code:
// Copyright Kevlin Henney, 2000-2005.
// Copyright Alexander Nasonov, 2006-2010.
// Copyright Antony Polukhin, 2011-2014.
//
// Distributed under 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)
//
// what:  lexical_cast custom keyword cast
// who:   contributed by Kevlin Henney,
//        enhanced with contributions from Terje Slettebo,
//        with additional fixes and suggestions from Gennaro Prota,
//        Beman Dawes, Dave Abrahams, Daryle Walker, Peter Dimov,
//        Alexander Nasonov, Antony Polukhin, Justin Viiret, Michael Hofmann,
//        Cheng Yang, Matthew Bradbury, David W. Birdsall, Pavel Korzh and other Boosters
// when:  November 2000, March 2003, June 2005, June 2006, March 2011 - 2014

#ifndef BOOST_LEXICAL_CAST_DETAIL_CONVERTER_LEXICAL_HPP
#define BOOST_LEXICAL_CAST_DETAIL_CONVERTER_LEXICAL_HPP

#include <boost/config.hpp>
#ifdef BOOST_HAS_PRAGMA_ONCE
#   pragma once
#endif

#if defined(BOOST_NO_STRINGSTREAM) || defined(BOOST_NO_STD_WSTRING)
#define BOOST_LCAST_NO_WCHAR_T
#endif

#include <cstddef>
#include <string>
#include <boost/limits.hpp>
#include <boost/mpl/bool.hpp>
#include <boost/mpl/identity.hpp>
#include <boost/mpl/if.hpp>
#include <boost/type_traits/is_integral.hpp>
#include <boost/type_traits/is_float.hpp>
#include <boost/type_traits/has_left_shift.hpp>
#include <boost/type_traits/has_right_shift.hpp>
#include <boost/static_assert.hpp>
#include <boost/detail/lcast_precision.hpp>

#include <boost/lexical_cast/detail/widest_char.hpp>
#include <boost/lexical_cast/detail/is_character.hpp>

#ifndef BOOST_NO_CXX11_HDR_ARRAY
#include <array>
#endif

#include <boost/array.hpp>
#include <boost/range/iterator_range_core.hpp>
#include <boost/container/container_fwd.hpp>

#include <boost/lexical_cast/detail/converter_lexical_streams.hpp>

namespace boost {

    namespace detail // normalize_single_byte_char<Char>
    {
        // Converts signed/unsigned char to char
        template < class Char >
        struct normalize_single_byte_char
        {
            typedef Char type;
        };

        template <>
        struct normalize_single_byte_char< signed char >
        {
            typedef char type;
        };

        template <>
        struct normalize_single_byte_char< unsigned char >
        {
            typedef char type;
        };
    }

    namespace detail // deduce_character_type_later<T>
    {
        // Helper type, meaning that stram character for T must be deduced
        // at Stage 2 (See deduce_source_char<T> and deduce_target_char<T>)
        template < class T > struct deduce_character_type_later {};
    }

    namespace detail // stream_char_common<T>
    {
        // Selectors to choose stream character type (common for Source and Target)
        // Returns one of char, wchar_t, char16_t, char32_t or deduce_character_type_later<T> types
        // Executed on Stage 1 (See deduce_source_char<T> and deduce_target_char<T>)
        template < typename Type >
        struct stream_char_common: public boost::mpl::if_c<
            boost::detail::is_character< Type >::value,
            Type,
            boost::detail::deduce_character_type_later< Type >
        > {};

        template < typename Char >
        struct stream_char_common< Char* >: public boost::mpl::if_c<
            boost::detail::is_character< Char >::value,
            Char,
            boost::detail::deduce_character_type_later< Char* >
        > {};

        template < typename Char >
        struct stream_char_common< const Char* >: public boost::mpl::if_c<
            boost::detail::is_character< Char >::value,
            Char,
            boost::detail::deduce_character_type_later< const Char* >
        > {};

        template < typename Char >
        struct stream_char_common< boost::iterator_range< Char* > >: public boost::mpl::if_c<
            boost::detail::is_character< Char >::value,
            Char,
            boost::detail::deduce_character_type_later< boost::iterator_range< Char* > >
        > {};

        template < typename Char >
        struct stream_char_common< boost::iterator_range< const Char* > >: public boost::mpl::if_c<
            boost::detail::is_character< Char >::value,
            Char,
            boost::detail::deduce_character_type_later< boost::iterator_range< const Char* > >
        > {};

        template < class Char, class Traits, class Alloc >
        struct stream_char_common< std::basic_string< Char, Traits, Alloc > >
        {
            typedef Char type;
        };

        template < class Char, class Traits, class Alloc >
        struct stream_char_common< boost::container::basic_string< Char, Traits, Alloc > >
        {
            typedef Char type;
        };

        template < typename Char, std::size_t N >
        struct stream_char_common< boost::array< Char, N > >: public boost::mpl::if_c<
            boost::detail::is_character< Char >::value,
            Char,
            boost::detail::deduce_character_type_later< boost::array< Char, N > >
        > {};

        template < typename Char, std::size_t N >
        struct stream_char_common< boost::array< const Char, N > >: public boost::mpl::if_c<
            boost::detail::is_character< Char >::value,
            Char,
            boost::detail::deduce_character_type_later< boost::array< const Char, N > >
        > {};

#ifndef BOOST_NO_CXX11_HDR_ARRAY
        template < typename Char, std::size_t N >
        struct stream_char_common< std::array<Char, N > >: public boost::mpl::if_c<
            boost::detail::is_character< Char >::value,
            Char,
            boost::detail::deduce_character_type_later< std::array< Char, N > >
        > {};

        template < typename Char, std::size_t N >
        struct stream_char_common< std::array< const Char, N > >: public boost::mpl::if_c<
            boost::detail::is_character< Char >::value,
            Char,
            boost::detail::deduce_character_type_later< std::array< const Char, N > >
        > {};
#endif

#ifdef BOOST_HAS_INT128
        template <> struct stream_char_common< boost::int128_type >: public boost::mpl::identity< char > {};
        template <> struct stream_char_common< boost::uint128_type >: public boost::mpl::identity< char > {};
#endif

#if !defined(BOOST_LCAST_NO_WCHAR_T) && defined(BOOST_NO_INTRINSIC_WCHAR_T)
        template <>
        struct stream_char_common< wchar_t >
        {
            typedef char type;
        };
#endif
    }

    namespace detail // deduce_source_char_impl<T>
    {
        // If type T is `deduce_character_type_later` type, then tries to deduce
        // character type using boost::has_left_shift<T> metafunction.
        // Otherwise supplied type T is a character type, that must be normalized
        // using normalize_single_byte_char<Char>.
        // Executed at Stage 2  (See deduce_source_char<T> and deduce_target_char<T>)
        template < class Char >
        struct deduce_source_char_impl
        {
            typedef BOOST_DEDUCED_TYPENAME boost::detail::normalize_single_byte_char< Char >::type type;
        };

        template < class T >
        struct deduce_source_char_impl< deduce_character_type_later< T > >
        {
            typedef boost::has_left_shift< std::basic_ostream< char >, T > result_t;

#if defined(BOOST_LCAST_NO_WCHAR_T)
            BOOST_STATIC_ASSERT_MSG((result_t::value),
                "Source type is not std::ostream`able and std::wostream`s are not supported by your STL implementation");
            typedef char type;
#else
            typedef BOOST_DEDUCED_TYPENAME boost::mpl::if_c<
                result_t::value, char, wchar_t
            >::type type;

            BOOST_STATIC_ASSERT_MSG((result_t::value || boost::has_left_shift< std::basic_ostream< type >, T >::value),
                "Source type is neither std::ostream`able nor std::wostream`able");
#endif
        };
    }

    namespace detail  // deduce_target_char_impl<T>
    {
        // If type T is `deduce_character_type_later` type, then tries to deduce
        // character type using boost::has_right_shift<T> metafunction.
        // Otherwise supplied type T is a character type, that must be normalized
        // using normalize_single_byte_char<Char>.
        // Executed at Stage 2  (See deduce_source_char<T> and deduce_target_char<T>)
        template < class Char >
        struct deduce_target_char_impl
        {
            typedef BOOST_DEDUCED_TYPENAME normalize_single_byte_char< Char >::type type;
        };

        template < class T >
        struct deduce_target_char_impl< deduce_character_type_later<T> >
        {
            typedef boost::has_right_shift<std::basic_istream<char>, T > result_t;

#if defined(BOOST_LCAST_NO_WCHAR_T)
            BOOST_STATIC_ASSERT_MSG((result_t::value),
                "Target type is not std::istream`able and std::wistream`s are not supported by your STL implementation");
            typedef char type;
#else
            typedef BOOST_DEDUCED_TYPENAME boost::mpl::if_c<
                result_t::value, char, wchar_t
            >::type type;

            BOOST_STATIC_ASSERT_MSG((result_t::value || boost::has_right_shift<std::basic_istream<wchar_t>, T >::value),
                "Target type is neither std::istream`able nor std::wistream`able");
#endif
        };
    }

    namespace detail  // deduce_target_char<T> and deduce_source_char<T>
    {
        // We deduce stream character types in two stages.
        //
        // Stage 1 is common for Target and Source. At Stage 1 we get
        // non normalized character type (may contain unsigned/signed char)
        // or deduce_character_type_later<T> where T is the original type.
        // Stage 1 is executed by stream_char_common<T>
        //
        // At Stage 2 we normalize character types or try to deduce character
        // type using metafunctions.
        // Stage 2 is executed by deduce_target_char_impl<T> and
        // deduce_source_char_impl<T>
        //
        // deduce_target_char<T> and deduce_source_char<T> functions combine
        // both stages

        template < class T >
        struct deduce_target_char
        {
            typedef BOOST_DEDUCED_TYPENAME stream_char_common< T >::type stage1_type;
            typedef BOOST_DEDUCED_TYPENAME deduce_target_char_impl< stage1_type >::type stage2_type;

            typedef stage2_type type;
        };

        template < class T >
        struct deduce_source_char
        {
            typedef BOOST_DEDUCED_TYPENAME stream_char_common< T >::type stage1_type;
            typedef BOOST_DEDUCED_TYPENAME deduce_source_char_impl< stage1_type >::type stage2_type;

            typedef stage2_type type;
        };
    }

    namespace detail // extract_char_traits template
    {
        // We are attempting to get char_traits<> from T
        // template parameter. Otherwise we'll be using std::char_traits<Char>
        template < class Char, class T >
        struct extract_char_traits
                : boost::false_type
        {
            typedef std::char_traits< Char > trait_t;
        };

        template < class Char, class Traits, class Alloc >
        struct extract_char_traits< Char, std::basic_string< Char, Traits, Alloc > >
            : boost::true_type
        {
            typedef Traits trait_t;
        };

        template < class Char, class Traits, class Alloc>
        struct extract_char_traits< Char, boost::container::basic_string< Char, Traits, Alloc > >
            : boost::true_type
        {
            typedef Traits trait_t;
        };
    }

    namespace detail // array_to_pointer_decay<T>
    {
        template<class T>
        struct array_to_pointer_decay
        {
            typedef T type;
        };

        template<class T, std::size_t N>
        struct array_to_pointer_decay<T[N]>
        {
            typedef const T * type;
        };
    }

    namespace detail // lcast_src_length
    {
        // Return max. length of string representation of Source;
        template< class Source,         // Source type of lexical_cast.
                  class Enable = void   // helper type
                >
        struct lcast_src_length
        {
            BOOST_STATIC_CONSTANT(std::size_t, value = 1);
        };

        // Helper for integral types.
        // Notes on length calculation:
        // Max length for 32bit int with grouping "\1" and thousands_sep ',':
        // "-2,1,4,7,4,8,3,6,4,7"
        //  ^                    - is_signed
        //   ^                   - 1 digit not counted by digits10
        //    ^^^^^^^^^^^^^^^^^^ - digits10 * 2
        //
        // Constant is_specialized is used instead of constant 1
        // to prevent buffer overflow in a rare case when
        // <boost/limits.hpp> doesn't add missing specialization for
        // numeric_limits<T> for some integral type T.
        // When is_specialized is false, the whole expression is 0.
        template <class Source>
        struct lcast_src_length<
                    Source, BOOST_DEDUCED_TYPENAME boost::enable_if<boost::is_integral<Source> >::type
                >
        {
#ifndef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS
            BOOST_STATIC_CONSTANT(std::size_t, value =
                  std::numeric_limits<Source>::is_signed +
                  std::numeric_limits<Source>::is_specialized + /* == 1 */
                  std::numeric_limits<Source>::digits10 * 2
              );
#else
            BOOST_STATIC_CONSTANT(std::size_t, value = 156);
            BOOST_STATIC_ASSERT(sizeof(Source) * CHAR_BIT <= 256);
#endif
        };

        // Helper for floating point types.
        // -1.23456789e-123456
        // ^                   sign
        //  ^                  leading digit
        //   ^                 decimal point
        //    ^^^^^^^^         lcast_precision<Source>::value
        //            ^        "e"
        //             ^       exponent sign
        //              ^^^^^^ exponent (assumed 6 or less digits)
        // sign + leading digit + decimal point + "e" + exponent sign == 5
        template<class Source>
        struct lcast_src_length<
                Source, BOOST_DEDUCED_TYPENAME boost::enable_if<boost::is_float<Source> >::type
            >
        {

#ifndef BOOST_LCAST_NO_COMPILE_TIME_PRECISION
            BOOST_STATIC_ASSERT(
                    std::numeric_limits<Source>::max_exponent10 <=  999999L &&
                    std::numeric_limits<Source>::min_exponent10 >= -999999L
                );

            BOOST_STATIC_CONSTANT(std::size_t, value =
                    5 + lcast_precision<Source>::value + 6
                );
#else // #ifndef BOOST_LCAST_NO_COMPILE_TIME_PRECISION
            BOOST_STATIC_CONSTANT(std::size_t, value = 156);
#endif // #ifndef BOOST_LCAST_NO_COMPILE_TIME_PRECISION
        };
    }

    namespace detail // lexical_cast_stream_traits<Source, Target>
    {
        template <class Source, class Target>
        struct lexical_cast_stream_traits {
            typedef BOOST_DEDUCED_TYPENAME boost::detail::array_to_pointer_decay<Source>::type src;
            typedef BOOST_DEDUCED_TYPENAME boost::remove_cv<src>::type            no_cv_src;

            typedef boost::detail::deduce_source_char<no_cv_src>                           deduce_src_char_metafunc;
            typedef BOOST_DEDUCED_TYPENAME deduce_src_char_metafunc::type           src_char_t;
            typedef BOOST_DEDUCED_TYPENAME boost::detail::deduce_target_char<Target>::type target_char_t;

            typedef BOOST_DEDUCED_TYPENAME boost::detail::widest_char<
                target_char_t, src_char_t
            >::type char_type;

#if !defined(BOOST_NO_CXX11_CHAR16_T) && defined(BOOST_NO_CXX11_UNICODE_LITERALS)
            BOOST_STATIC_ASSERT_MSG(( !boost::is_same<char16_t, src_char_t>::value
                                        && !boost::is_same<char16_t, target_char_t>::value),
                "Your compiler does not have full support for char16_t" );
#endif
#if !defined(BOOST_NO_CXX11_CHAR32_T) && defined(BOOST_NO_CXX11_UNICODE_LITERALS)
            BOOST_STATIC_ASSERT_MSG(( !boost::is_same<char32_t, src_char_t>::value
                                        && !boost::is_same<char32_t, target_char_t>::value),
                "Your compiler does not have full support for char32_t" );
#endif

            typedef BOOST_DEDUCED_TYPENAME boost::mpl::if_c<
                boost::detail::extract_char_traits<char_type, Target>::value,
                BOOST_DEDUCED_TYPENAME boost::detail::extract_char_traits<char_type, Target>,
                BOOST_DEDUCED_TYPENAME boost::detail::extract_char_traits<char_type, no_cv_src>
            >::type::trait_t traits;

            typedef boost::mpl::bool_
            	<
                boost::is_same<char, src_char_t>::value &&                                 // source is not a wide character based type
                (sizeof(char) != sizeof(target_char_t)) &&  // target type is based on wide character
                (!(boost::detail::is_character<no_cv_src>::value))
            	> is_string_widening_required_t;

            typedef boost::mpl::bool_
            	<
            	!(boost::is_integral<no_cv_src>::value ||
                  boost::detail::is_character<
                    BOOST_DEDUCED_TYPENAME deduce_src_char_metafunc::stage1_type          // if we did not get character type at stage1
                  >::value                                                           // then we have no optimization for that type
            	 )
            	> is_source_input_not_optimized_t;

            // If we have an optimized conversion for
            // Source, we do not need to construct stringbuf.
            BOOST_STATIC_CONSTANT(bool, requires_stringbuf =
            	(is_string_widening_required_t::value || is_source_input_not_optimized_t::value)
            );

            typedef boost::detail::lcast_src_length<no_cv_src> len_t;
        };
    }

    namespace detail
    {
        template<typename Target, typename Source>
        struct lexical_converter_impl
        {
            typedef lexical_cast_stream_traits<Source, Target>  stream_trait;

            typedef detail::lexical_istream_limited_src<
                BOOST_DEDUCED_TYPENAME stream_trait::char_type,
                BOOST_DEDUCED_TYPENAME stream_trait::traits,
                stream_trait::requires_stringbuf,
                stream_trait::len_t::value + 1
            > i_interpreter_type;

            typedef detail::lexical_ostream_limited_src<
                BOOST_DEDUCED_TYPENAME stream_trait::char_type,
                BOOST_DEDUCED_TYPENAME stream_trait::traits
            > o_interpreter_type;

            static inline bool try_convert(const Source& arg, Target& result) {
                i_interpreter_type i_interpreter;

                // Disabling ADL, by directly specifying operators.
                if (!(i_interpreter.operator <<(arg)))
                    return false;

                o_interpreter_type out(i_interpreter.cbegin(), i_interpreter.cend());

                // Disabling ADL, by directly specifying operators.
                if(!(out.operator >>(result)))
                    return false;

                return true;
            }
        };
    }

} // namespace boost

#undef BOOST_LCAST_NO_WCHAR_T

#endif // BOOST_LEXICAL_CAST_DETAIL_CONVERTER_LEXICAL_HPP


code:
// Copyright Kevlin Henney, 2000-2005.
// Copyright Alexander Nasonov, 2006-2010.
// Copyright Antony Polukhin, 2011-2016.
//
// Distributed under 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)
//
// what:  lexical_cast custom keyword cast
// who:   contributed by Kevlin Henney,
//        enhanced with contributions from Terje Slettebo,
//        with additional fixes and suggestions from Gennaro Prota,
//        Beman Dawes, Dave Abrahams, Daryle Walker, Peter Dimov,
//        Alexander Nasonov, Antony Polukhin, Justin Viiret, Michael Hofmann,
//        Cheng Yang, Matthew Bradbury, David W. Birdsall, Pavel Korzh and other Boosters
// when:  November 2000, March 2003, June 2005, June 2006, March 2011 - 2014, Nowember 2016

#ifndef BOOST_LEXICAL_CAST_DETAIL_CONVERTER_LEXICAL_STREAMS_HPP
#define BOOST_LEXICAL_CAST_DETAIL_CONVERTER_LEXICAL_STREAMS_HPP

#include <boost/config.hpp>
#ifdef BOOST_HAS_PRAGMA_ONCE
#   pragma once
#endif

#if defined(BOOST_NO_STRINGSTREAM) || defined(BOOST_NO_STD_WSTRING)
#define BOOST_LCAST_NO_WCHAR_T
#endif

#include <cstddef>
#include <string>
#include <cstring>
#include <cstdio>
#include <boost/limits.hpp>
#include <boost/mpl/if.hpp>
#include <boost/type_traits/is_pointer.hpp>
#include <boost/static_assert.hpp>
#include <boost/detail/workaround.hpp>

#ifndef BOOST_NO_STD_LOCALE
#   include <locale>
#else
#   ifndef BOOST_LEXICAL_CAST_ASSUME_C_LOCALE
        // Getting error at this point means, that your STL library is old/lame/misconfigured.
        // If nothing can be done with STL library, define BOOST_LEXICAL_CAST_ASSUME_C_LOCALE,
        // but beware: lexical_cast will understand only 'C' locale delimeters and thousands
        // separators.
#       error "Unable to use <locale> header. Define BOOST_LEXICAL_CAST_ASSUME_C_LOCALE to force "
#       error "boost::lexical_cast to use only 'C' locale during conversions."
#   endif
#endif

#ifdef BOOST_NO_STRINGSTREAM
#include <strstream>
#else
#include <sstream>
#endif

#include <boost/lexical_cast/detail/lcast_char_constants.hpp>
#include <boost/lexical_cast/detail/lcast_unsigned_converters.hpp>
#include <boost/lexical_cast/detail/inf_nan.hpp>

#include <istream>

#ifndef BOOST_NO_CXX11_HDR_ARRAY
#include <array>
#endif

#include <boost/array.hpp>
#include <boost/type_traits/make_unsigned.hpp>
#include <boost/type_traits/is_integral.hpp>
#include <boost/type_traits/is_float.hpp>
#include <boost/range/iterator_range_core.hpp>
#include <boost/container/container_fwd.hpp>
#include <boost/integer.hpp>
#include <boost/detail/basic_pointerbuf.hpp>
#include <boost/noncopyable.hpp>
#ifndef BOOST_NO_CWCHAR
#   include <cwchar>
#endif

namespace boost {

    namespace detail // basic_unlockedbuf
    {
        // acts as a stream buffer which wraps around a pair of pointers
        // and gives acces to internals
        template <class BufferType, class CharT>
        class basic_unlockedbuf : public basic_pointerbuf<CharT, BufferType> {
        public:
           typedef basic_pointerbuf<CharT, BufferType> base_type;
           typedef BOOST_DEDUCED_TYPENAME base_type::streamsize streamsize;

#ifndef BOOST_NO_USING_TEMPLATE
            using base_type::pptr;
            using base_type::pbase;
            using base_type::setbuf;
#else
            charT* pptr() const { return base_type::pptr(); }
            charT* pbase() const { return base_type::pbase(); }
            BufferType* setbuf(char_type* s, streamsize n) { return base_type::setbuf(s, n); }
#endif
        };
    }

    namespace detail
    {
        struct do_not_construct_out_buffer_t{};
        struct do_not_construct_out_stream_t{
            do_not_construct_out_stream_t(do_not_construct_out_buffer_t*){}
        };

        template <class CharT, class Traits>
        struct out_stream_helper_trait {
#if defined(BOOST_NO_STRINGSTREAM)
            typedef std::ostream                                                    out_stream_t;
            typedef basic_unlockedbuf<std::strstreambuf, char>                      stringbuffer_t;
#elif defined(BOOST_NO_STD_LOCALE)
            typedef std::ostream                                                    out_stream_t;
            typedef basic_unlockedbuf<std::stringbuf, char>                         stringbuffer_t;
            typedef basic_unlockedbuf<std::streambuf, char>                         buffer_t;
#else
            typedef std::basic_ostream<CharT, Traits>                               out_stream_t;
            typedef basic_unlockedbuf<std::basic_stringbuf<CharT, Traits>, CharT>   stringbuffer_t;
            typedef basic_unlockedbuf<std::basic_streambuf<CharT, Traits>, CharT>   buffer_t;
#endif
        };
    }

    namespace detail // optimized stream wrappers
    {
        template< class CharT // a result of widest_char transformation
                , class Traits
                , bool RequiresStringbuffer
                , std::size_t CharacterBufferSize
                >
        class lexical_istream_limited_src: boost::noncopyable {
            typedef BOOST_DEDUCED_TYPENAME boost::mpl::if_c<
                RequiresStringbuffer,
                BOOST_DEDUCED_TYPENAME out_stream_helper_trait<CharT, Traits>::out_stream_t,
                do_not_construct_out_stream_t
            >::type deduced_out_stream_t;

            typedef BOOST_DEDUCED_TYPENAME boost::mpl::if_c<
                RequiresStringbuffer,
                BOOST_DEDUCED_TYPENAME out_stream_helper_trait<CharT, Traits>::stringbuffer_t,
                do_not_construct_out_buffer_t
            >::type deduced_out_buffer_t;

            deduced_out_buffer_t out_buffer;
            deduced_out_stream_t out_stream;
            CharT   buffer[CharacterBufferSize];

            // After the `operator <<`  finishes, `[start, finish)` is
            // the range to output by `operator >>`
            const CharT*  start;
            const CharT*  finish;

        public:
            lexical_istream_limited_src() BOOST_NOEXCEPT
              : out_buffer()
              , out_stream(&out_buffer)
              , start(buffer)
              , finish(buffer + CharacterBufferSize)
            {}

            const CharT* cbegin() const BOOST_NOEXCEPT {
                return start;
            }

            const CharT* cend() const BOOST_NOEXCEPT {
                return finish;
            }

        private:
/************************************ HELPER FUNCTIONS FOR OPERATORS << ( ... ) ********************************/
            bool shl_char(CharT ch) BOOST_NOEXCEPT {
                Traits::assign(buffer[0], ch);
                finish = start + 1;
                return true;
            }

#ifndef BOOST_LCAST_NO_WCHAR_T
            template <class T>
            bool shl_char(T ch) {
                BOOST_STATIC_ASSERT_MSG(( sizeof(T) <= sizeof(CharT)) ,
                    "boost::lexical_cast does not support narrowing of char types."
                    "Use boost::locale instead" );
#ifndef BOOST_LEXICAL_CAST_ASSUME_C_LOCALE
                std::locale loc;
                CharT const w = BOOST_USE_FACET(std::ctype<CharT>, loc).widen(ch);
#else
                CharT const w = static_cast<CharT>(ch);
#endif
                Traits::assign(buffer[0], w);
                finish = start + 1;
                return true;
            }
#endif

            bool shl_char_array(CharT const* str) BOOST_NOEXCEPT {
                start = str;
                finish = start + Traits::length(str);
                return true;
            }

            template <class T>
            bool shl_char_array(T const* str) {
                BOOST_STATIC_ASSERT_MSG(( sizeof(T) <= sizeof(CharT)),
                    "boost::lexical_cast does not support narrowing of char types."
                    "Use boost::locale instead" );
                return shl_input_streamable(str);
            }

            bool shl_char_array_limited(CharT const* str, std::size_t max_size) BOOST_NOEXCEPT {
                start = str;
                finish = std::find(start, start + max_size, Traits::to_char_type(0));
                return true;
            }

            template<typename InputStreamable>
            bool shl_input_streamable(InputStreamable& input) {
#if defined(BOOST_NO_STRINGSTREAM) || defined(BOOST_NO_STD_LOCALE)
                // If you have compilation error at this point, than your STL library
                // does not support such conversions. Try updating it.
                BOOST_STATIC_ASSERT((boost::is_same<char, CharT>::value));
#endif

#ifndef BOOST_NO_EXCEPTIONS
                out_stream.exceptions(std::ios::badbit);
                try {
#endif
                bool const result = !(out_stream << input).fail();
                const deduced_out_buffer_t* const p = static_cast<deduced_out_buffer_t*>(
                    out_stream.rdbuf()
                );
                start = p->pbase();
                finish = p->pptr();
                return result;
#ifndef BOOST_NO_EXCEPTIONS
                } catch (const ::std::ios_base::failure& /*f*/) {
                    return false;
                }
#endif
            }

            template <class T>
            inline bool shl_unsigned(const T n) {
                CharT* tmp_finish = buffer + CharacterBufferSize;
                start = lcast_put_unsigned<Traits, T, CharT>(n, tmp_finish).convert();
                finish = tmp_finish;
                return true;
            }

            template <class T>
            inline bool shl_signed(const T n) {
                CharT* tmp_finish = buffer + CharacterBufferSize;
                typedef BOOST_DEDUCED_TYPENAME boost::make_unsigned<T>::type utype;
                CharT* tmp_start = lcast_put_unsigned<Traits, utype, CharT>(lcast_to_unsigned(n), tmp_finish).convert();
                if (n < 0) {
                    --tmp_start;
                    CharT const minus = lcast_char_constants<CharT>::minus;
                    Traits::assign(*tmp_start, minus);
                }
                start = tmp_start;
                finish = tmp_finish;
                return true;
            }

            template <class T, class SomeCharT>
            bool shl_real_type(const T& val, SomeCharT* /*begin*/) {
                lcast_set_precision(out_stream, &val);
                return shl_input_streamable(val);
            }

            bool shl_real_type(float val, char* begin) {
                using namespace std;
                const double val_as_double = val;
                finish = start +
#if defined(_MSC_VER) && (_MSC_VER >= 1400) && !defined(__SGI_STL_PORT) && !defined(_STLPORT_VERSION)
                    sprintf_s(begin, CharacterBufferSize,
#else
                    sprintf(begin,
#endif
                    "%.*g", static_cast<int>(boost::detail::lcast_get_precision<float>()), val_as_double);
                return finish > start;
            }

            bool shl_real_type(double val, char* begin) {
                using namespace std;
                finish = start +
#if defined(_MSC_VER) && (_MSC_VER >= 1400) && !defined(__SGI_STL_PORT) && !defined(_STLPORT_VERSION)
                    sprintf_s(begin, CharacterBufferSize,
#else
                    sprintf(begin,
#endif
                    "%.*g", static_cast<int>(boost::detail::lcast_get_precision<double>()), val);
                return finish > start;
            }

#ifndef __MINGW32__
            bool shl_real_type(long double val, char* begin) {
                using namespace std;
                finish = start +
#if defined(_MSC_VER) && (_MSC_VER >= 1400) && !defined(__SGI_STL_PORT) && !defined(_STLPORT_VERSION)
                    sprintf_s(begin, CharacterBufferSize,
#else
                    sprintf(begin,
#endif
                    "%.*Lg", static_cast<int>(boost::detail::lcast_get_precision<long double>()), val );
                return finish > start;
            }
#endif

#if !defined(BOOST_LCAST_NO_WCHAR_T) && !defined(BOOST_NO_SWPRINTF) && !defined(__MINGW32__)
            bool shl_real_type(float val, wchar_t* begin) {
                using namespace std;
                const double val_as_double = val;
                finish = start + swprintf(begin, CharacterBufferSize,
                                       L"%.*g",
                                       static_cast<int>(boost::detail::lcast_get_precision<float >()),
                                       val_as_double );
                return finish > start;
            }

            bool shl_real_type(double val, wchar_t* begin) {
                using namespace std;
                finish = start + swprintf(begin, CharacterBufferSize,
                                          L"%.*g", static_cast<int>(boost::detail::lcast_get_precision<double >()), val );
                return finish > start;
            }

            bool shl_real_type(long double val, wchar_t* begin) {
                using namespace std;
                finish = start + swprintf(begin, CharacterBufferSize,
                                          L"%.*Lg", static_cast<int>(boost::detail::lcast_get_precision<long double >()), val );
                return finish > start;
            }
#endif
            template <class T>
            bool shl_real(T val) {
                CharT* tmp_finish = buffer + CharacterBufferSize;
                if (put_inf_nan(buffer, tmp_finish, val)) {
                    finish = tmp_finish;
                    return true;
                }

                return shl_real_type(val, static_cast<CharT*>(buffer));
            }

/************************************ OPERATORS << ( ... ) ********************************/
        public:
            template<class Alloc>
            bool operator<<(std::basic_string<CharT,Traits,Alloc> const& str) BOOST_NOEXCEPT {
                start = str.data();
                finish = start + str.length();
                return true;
            }

            template<class Alloc>
            bool operator<<(boost::container::basic_string<CharT,Traits,Alloc> const& str) BOOST_NOEXCEPT {
                start = str.data();
                finish = start + str.length();
                return true;
            }

            bool operator<<(bool value) BOOST_NOEXCEPT {
                CharT const czero = lcast_char_constants<CharT>::zero;
                Traits::assign(buffer[0], Traits::to_char_type(czero + value));
                finish = start + 1;
                return true;
            }

            template <class C>
            BOOST_DEDUCED_TYPENAME boost::disable_if<boost::is_const<C>, bool>::type
            operator<<(const iterator_range<C*>& rng) BOOST_NOEXCEPT {
                return (*this) << iterator_range<const C*>(rng.begin(), rng.end());
            }

            bool operator<<(const iterator_range<const CharT*>& rng) BOOST_NOEXCEPT {
                start = rng.begin();
                finish = rng.end();
                return true;
            }

            bool operator<<(const iterator_range<const signed char*>& rng) BOOST_NOEXCEPT {
                return (*this) << iterator_range<const char*>(
                    reinterpret_cast<const char*>(rng.begin()),
                    reinterpret_cast<const char*>(rng.end())
                );
            }

            bool operator<<(const iterator_range<const unsigned char*>& rng) BOOST_NOEXCEPT {
                return (*this) << iterator_range<const char*>(
                    reinterpret_cast<const char*>(rng.begin()),
                    reinterpret_cast<const char*>(rng.end())
                );
            }

            bool operator<<(char ch)                    { return shl_char(ch); }
            bool operator<<(unsigned char ch)           { return ((*this) << static_cast<char>(ch)); }
            bool operator<<(signed char ch)             { return ((*this) << static_cast<char>(ch)); }
#if !defined(BOOST_LCAST_NO_WCHAR_T)
            bool operator<<(wchar_t const* str)         { return shl_char_array(str); }
            bool operator<<(wchar_t * str)              { return shl_char_array(str); }
#ifndef BOOST_NO_INTRINSIC_WCHAR_T
            bool operator<<(wchar_t ch)                 { return shl_char(ch); }
#endif
#endif
#if !defined(BOOST_NO_CXX11_CHAR16_T) && !defined(BOOST_NO_CXX11_UNICODE_LITERALS)
            bool operator<<(char16_t ch)                { return shl_char(ch); }
            bool operator<<(char16_t * str)             { return shl_char_array(str); }
            bool operator<<(char16_t const * str)       { return shl_char_array(str); }
#endif
#if !defined(BOOST_NO_CXX11_CHAR32_T) && !defined(BOOST_NO_CXX11_UNICODE_LITERALS)
            bool operator<<(char32_t ch)                { return shl_char(ch); }
            bool operator<<(char32_t * str)             { return shl_char_array(str); }
            bool operator<<(char32_t const * str)       { return shl_char_array(str); }
#endif
            bool operator<<(unsigned char const* ch)    { return ((*this) << reinterpret_cast<char const*>(ch)); }
            bool operator<<(unsigned char * ch)         { return ((*this) << reinterpret_cast<char *>(ch)); }
            bool operator<<(signed char const* ch)      { return ((*this) << reinterpret_cast<char const*>(ch)); }
            bool operator<<(signed char * ch)           { return ((*this) << reinterpret_cast<char *>(ch)); }
            bool operator<<(char const* str)            { return shl_char_array(str); }
            bool operator<<(char* str)                  { return shl_char_array(str); }
            bool operator<<(short n)                    { return shl_signed(n); }
            bool operator<<(int n)                      { return shl_signed(n); }
            bool operator<<(long n)                     { return shl_signed(n); }
            bool operator<<(unsigned short n)           { return shl_unsigned(n); }
            bool operator<<(unsigned int n)             { return shl_unsigned(n); }
            bool operator<<(unsigned long n)            { return shl_unsigned(n); }

#if defined(BOOST_HAS_LONG_LONG)
            bool operator<<(boost::ulong_long_type n)   { return shl_unsigned(n); }
            bool operator<<(boost::long_long_type n)    { return shl_signed(n); }
#elif defined(BOOST_HAS_MS_INT64)
            bool operator<<(unsigned __int64 n)         { return shl_unsigned(n); }
            bool operator<<(         __int64 n)         { return shl_signed(n); }
#endif

#ifdef BOOST_HAS_INT128
            bool operator<<(const boost::uint128_type& n)   { return shl_unsigned(n); }
            bool operator<<(const boost::int128_type& n)    { return shl_signed(n); }
#endif
            bool operator<<(float val)                  { return shl_real(val); }
            bool operator<<(double val)                 { return shl_real(val); }
            bool operator<<(long double val)            {
#ifndef __MINGW32__
                return shl_real(val);
#else
                return shl_real(static_cast<double>(val));
#endif
            }

            // Adding constness to characters. Constness does not change layout
            template <class C, std::size_t N>
            BOOST_DEDUCED_TYPENAME boost::disable_if<boost::is_const<C>, bool>::type
            operator<<(boost::array<C, N> const& input) BOOST_NOEXCEPT {
                BOOST_STATIC_ASSERT_MSG(
                    (sizeof(boost::array<const C, N>) == sizeof(boost::array<C, N>)),
                    "boost::array<C, N> and boost::array<const C, N> must have exactly the same layout."
                );
                return ((*this) << reinterpret_cast<boost::array<const C, N> const& >(input));
            }

            template <std::size_t N>
            bool operator<<(boost::array<const CharT, N> const& input) BOOST_NOEXCEPT {
                return shl_char_array_limited(input.data(), N);
            }

            template <std::size_t N>
            bool operator<<(boost::array<const unsigned char, N> const& input) BOOST_NOEXCEPT {
                return ((*this) << reinterpret_cast<boost::array<const char, N> const& >(input));
            }

            template <std::size_t N>
            bool operator<<(boost::array<const signed char, N> const& input) BOOST_NOEXCEPT {
                return ((*this) << reinterpret_cast<boost::array<const char, N> const& >(input));
            }

#ifndef BOOST_NO_CXX11_HDR_ARRAY
            // Making a Boost.Array from std::array
            template <class C, std::size_t N>
            bool operator<<(std::array<C, N> const& input) BOOST_NOEXCEPT {
                BOOST_STATIC_ASSERT_MSG(
                    (sizeof(std::array<C, N>) == sizeof(boost::array<C, N>)),
                    "std::array and boost::array must have exactly the same layout. "
                    "Bug in implementation of std::array or boost::array."
                );
                return ((*this) << reinterpret_cast<boost::array<C, N> const& >(input));
            }
#endif
            template <class InStreamable>
            bool operator<<(const InStreamable& input)  { return shl_input_streamable(input); }
        };

        template <class CharT, class Traits>
        class lexical_ostream_limited_src: boost::noncopyable {
            //`[start, finish)` is the range to output by `operator >>`
            const CharT*        start;
            const CharT* const  finish;

        public:
            lexical_ostream_limited_src(const CharT* begin, const CharT* end) BOOST_NOEXCEPT
              : start(begin)
              , finish(end)
            {}

/************************************ HELPER FUNCTIONS FOR OPERATORS >> ( ... ) ********************************/
        private:
            template <typename Type>
            bool shr_unsigned(Type& output) {
                if (start == finish) return false;
                CharT const minus = lcast_char_constants<CharT>::minus;
                CharT const plus = lcast_char_constants<CharT>::plus;
                bool const has_minus = Traits::eq(minus, *start);

                /* We won`t use `start' any more, so no need in decrementing it after */
                if (has_minus || Traits::eq(plus, *start)) {
                    ++start;
                }

                bool const succeed = lcast_ret_unsigned<Traits, Type, CharT>(output, start, finish).convert();

                if (has_minus) {
                    output = static_cast<Type>(0u - output);
                }

                return succeed;
            }

            template <typename Type>
            bool shr_signed(Type& output) {
                if (start == finish) return false;
                CharT const minus = lcast_char_constants<CharT>::minus;
                CharT const plus = lcast_char_constants<CharT>::plus;
                typedef BOOST_DEDUCED_TYPENAME make_unsigned<Type>::type utype;
                utype out_tmp = 0;
                bool const has_minus = Traits::eq(minus, *start);

                /* We won`t use `start' any more, so no need in decrementing it after */
                if (has_minus || Traits::eq(plus, *start)) {
                    ++start;
                }

                bool succeed = lcast_ret_unsigned<Traits, utype, CharT>(out_tmp, start, finish).convert();
                if (has_minus) {
                    utype const comp_val = (static_cast<utype>(1) << std::numeric_limits<Type>::digits);
                    succeed = succeed && out_tmp<=comp_val;
                    output = static_cast<Type>(0u - out_tmp);
                } else {
                    utype const comp_val = static_cast<utype>((std::numeric_limits<Type>::max)());
                    succeed = succeed && out_tmp<=comp_val;
                    output = static_cast<Type>(out_tmp);
                }
                return succeed;
            }

            template<typename InputStreamable>
            bool shr_using_base_class(InputStreamable& output)
            {
                BOOST_STATIC_ASSERT_MSG(
                    (!boost::is_pointer<InputStreamable>::value),
                    "boost::lexical_cast can not convert to pointers"
                );

#if defined(BOOST_NO_STRINGSTREAM) || defined(BOOST_NO_STD_LOCALE)
                BOOST_STATIC_ASSERT_MSG((boost::is_same<char, CharT>::value),
                    "boost::lexical_cast can not convert, because your STL library does not "
                    "support such conversions. Try updating it."
                );
#endif

#if defined(BOOST_NO_STRINGSTREAM)
                std::istrstream stream(start, finish - start);
#else
                BOOST_DEDUCED_TYPENAME out_stream_helper_trait<CharT, Traits>::buffer_t buf;
                // Usually `istream` and `basic_istream` do not modify
                // content of buffer; `buffer_t` assures that this is true
                buf.setbuf(const_cast<CharT*>(start), finish - start);
#if defined(BOOST_NO_STD_LOCALE)
                std::istream stream(&buf);
#else
                std::basic_istream<CharT, Traits> stream(&buf);
#endif // BOOST_NO_STD_LOCALE
#endif // BOOST_NO_STRINGSTREAM

#ifndef BOOST_NO_EXCEPTIONS
                stream.exceptions(std::ios::badbit);
                try {
#endif
                stream.unsetf(std::ios::skipws);
                lcast_set_precision(stream, static_cast<InputStreamable*>(0));

                return (stream >> output)
                    && (stream.get() == Traits::eof());

#ifndef BOOST_NO_EXCEPTIONS
                } catch (const ::std::ios_base::failure& /*f*/) {
                    return false;
                }
#endif
            }

            template<class T>
            inline bool shr_xchar(T& output) BOOST_NOEXCEPT {
                BOOST_STATIC_ASSERT_MSG(( sizeof(CharT) == sizeof(T) ),
                    "boost::lexical_cast does not support narrowing of character types."
                    "Use boost::locale instead" );
                bool const ok = (finish - start == 1);
                if (ok) {
                    CharT out;
                    Traits::assign(out, *start);
                    output = static_cast<T>(out);
                }
                return ok;
            }

            template <std::size_t N, class ArrayT>
            bool shr_std_array(ArrayT& output) BOOST_NOEXCEPT {
                using namespace std;
                const std::size_t size = static_cast<std::size_t>(finish - start);
                if (size > N - 1) { // `-1` because we need to store \0 at the end
                    return false;
                }

                memcpy(&output[0], start, size * sizeof(CharT));
                output[size] = Traits::to_char_type(0);
                return true;
            }

/************************************ OPERATORS >> ( ... ) ********************************/
        public:
            bool operator>>(unsigned short& output)             { return shr_unsigned(output); }
            bool operator>>(unsigned int& output)               { return shr_unsigned(output); }
            bool operator>>(unsigned long int& output)          { return shr_unsigned(output); }
            bool operator>>(short& output)                      { return shr_signed(output); }
            bool operator>>(int& output)                        { return shr_signed(output); }
            bool operator>>(long int& output)                   { return shr_signed(output); }
#if defined(BOOST_HAS_LONG_LONG)
            bool operator>>(boost::ulong_long_type& output)     { return shr_unsigned(output); }
            bool operator>>(boost::long_long_type& output)      { return shr_signed(output); }
#elif defined(BOOST_HAS_MS_INT64)
            bool operator>>(unsigned __int64& output)           { return shr_unsigned(output); }
            bool operator>>(__int64& output)                    { return shr_signed(output); }
#endif

#ifdef BOOST_HAS_INT128
            bool operator>>(boost::uint128_type& output)        { return shr_unsigned(output); }
            bool operator>>(boost::int128_type& output)         { return shr_signed(output); }
#endif

            bool operator>>(char& output)                       { return shr_xchar(output); }
            bool operator>>(unsigned char& output)              { return shr_xchar(output); }
            bool operator>>(signed char& output)                { return shr_xchar(output); }
#if !defined(BOOST_LCAST_NO_WCHAR_T) && !defined(BOOST_NO_INTRINSIC_WCHAR_T)
            bool operator>>(wchar_t& output)                    { return shr_xchar(output); }
#endif
#if !defined(BOOST_NO_CXX11_CHAR16_T) && !defined(BOOST_NO_CXX11_UNICODE_LITERALS)
            bool operator>>(char16_t& output)                   { return shr_xchar(output); }
#endif
#if !defined(BOOST_NO_CXX11_CHAR32_T) && !defined(BOOST_NO_CXX11_UNICODE_LITERALS)
            bool operator>>(char32_t& output)                   { return shr_xchar(output); }
#endif
            template<class Alloc>
            bool operator>>(std::basic_string<CharT,Traits,Alloc>& str) {
                str.assign(start, finish); return true;
            }

            template<class Alloc>
            bool operator>>(boost::container::basic_string<CharT,Traits,Alloc>& str) {
                str.assign(start, finish); return true;
            }

            template <std::size_t N>
            bool operator>>(boost::array<CharT, N>& output) BOOST_NOEXCEPT {
                return shr_std_array<N>(output);
            }

            template <std::size_t N>
            bool operator>>(boost::array<unsigned char, N>& output) BOOST_NOEXCEPT {
                return ((*this) >> reinterpret_cast<boost::array<char, N>& >(output));
            }

            template <std::size_t N>
            bool operator>>(boost::array<signed char, N>& output) BOOST_NOEXCEPT {
                return ((*this) >> reinterpret_cast<boost::array<char, N>& >(output));
            }

#ifndef BOOST_NO_CXX11_HDR_ARRAY
            template <class C, std::size_t N>
            bool operator>>(std::array<C, N>& output) BOOST_NOEXCEPT {
                BOOST_STATIC_ASSERT_MSG(
                    (sizeof(std::array<C, N>) == sizeof(boost::array<C, N>)),
                    "std::array<C, N> and boost::array<C, N> must have exactly the same layout."
                );
                return ((*this) >> reinterpret_cast<boost::array<C, N>& >(output));
            }
#endif

            bool operator>>(bool& output) BOOST_NOEXCEPT {
                output = false; // Suppress warning about uninitalized variable

                if (start == finish) return false;
                CharT const zero = lcast_char_constants<CharT>::zero;
                CharT const plus = lcast_char_constants<CharT>::plus;
                CharT const minus = lcast_char_constants<CharT>::minus;

                const CharT* const dec_finish = finish - 1;
                output = Traits::eq(*dec_finish, zero + 1);
                if (!output && !Traits::eq(*dec_finish, zero)) {
                    return false; // Does not ends on '0' or '1'
                }

                if (start == dec_finish) return true;

                // We may have sign at the beginning
                if (Traits::eq(plus, *start) || (Traits::eq(minus, *start) && !output)) {
                    ++ start;
                }

                // Skipping zeros
                while (start != dec_finish) {
                    if (!Traits::eq(zero, *start)) {
                        return false; // Not a zero => error
                    }

                    ++ start;
                }

                return true;
            }

        private:
            // Not optimised converter
            template <class T>
            bool float_types_converter_internal(T& output) {
                if (parse_inf_nan(start, finish, output)) return true;
                bool const return_value = shr_using_base_class(output);

                /* Some compilers and libraries successfully
                 * parse 'inf', 'INFINITY', '1.0E', '1.0E-'...
                 * We are trying to provide a unified behaviour,
                 * so we just forbid such conversions (as some
                 * of the most popular compilers/libraries do)
                 * */
                CharT const minus = lcast_char_constants<CharT>::minus;
                CharT const plus = lcast_char_constants<CharT>::plus;
                CharT const capital_e = lcast_char_constants<CharT>::capital_e;
                CharT const lowercase_e = lcast_char_constants<CharT>::lowercase_e;
                if ( return_value &&
                     (
                        Traits::eq(*(finish-1), lowercase_e)                   // 1.0e
                        || Traits::eq(*(finish-1), capital_e)                  // 1.0E
                        || Traits::eq(*(finish-1), minus)                      // 1.0e- or 1.0E-
                        || Traits::eq(*(finish-1), plus)                       // 1.0e+ or 1.0E+
                     )
                ) return false;

                return return_value;
            }

        public:
            bool operator>>(float& output) { return float_types_converter_internal(output); }
            bool operator>>(double& output) { return float_types_converter_internal(output); }
            bool operator>>(long double& output) { return float_types_converter_internal(output); }

            // Generic istream-based algorithm.
            // lcast_streambuf_for_target<InputStreamable>::value is true.
            template <typename InputStreamable>
            bool operator>>(InputStreamable& output) {
                return shr_using_base_class(output);
            }
        };
    }
} // namespace boost

#undef BOOST_LCAST_NO_WCHAR_T

#endif // BOOST_LEXICAL_CAST_DETAIL_CONVERTER_LEXICAL_HPP


code:
// Copyright Kevlin Henney, 2000-2005.
// Copyright Alexander Nasonov, 2006-2010.
// Copyright Antony Polukhin, 2011-2016.
//
// Distributed under 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)
//
// what:  lexical_cast custom keyword cast
// who:   contributed by Kevlin Henney,
//        enhanced with contributions from Terje Slettebo,
//        with additional fixes and suggestions from Gennaro Prota,
//        Beman Dawes, Dave Abrahams, Daryle Walker, Peter Dimov,
//        Alexander Nasonov, Antony Polukhin, Justin Viiret, Michael Hofmann,
//        Cheng Yang, Matthew Bradbury, David W. Birdsall, Pavel Korzh and other Boosters
// when:  November 2000, March 2003, June 2005, June 2006, March 2011 - 2016

#ifndef BOOST_LEXICAL_CAST_DETAIL_CONVERTER_NUMERIC_HPP
#define BOOST_LEXICAL_CAST_DETAIL_CONVERTER_NUMERIC_HPP

#include <boost/config.hpp>
#ifdef BOOST_HAS_PRAGMA_ONCE
#   pragma once
#endif

#include <boost/limits.hpp>
#include <boost/mpl/eval_if.hpp>
#include <boost/mpl/identity.hpp>
#include <boost/mpl/if.hpp>
#include <boost/type_traits/make_unsigned.hpp>
#include <boost/type_traits/is_signed.hpp>
#include <boost/type_traits/is_integral.hpp>
#include <boost/type_traits/is_arithmetic.hpp>
#include <boost/type_traits/is_base_of.hpp>
#include <boost/type_traits/is_float.hpp>

#include <boost/numeric/conversion/cast.hpp>

namespace boost { namespace detail {

template <class Source >
struct detect_precision_loss
{
    typedef Source source_type;
    typedef boost::numeric::Trunc<Source> Rounder;
    typedef BOOST_DEDUCED_TYPENAME mpl::if_<
        boost::is_arithmetic<Source>, Source, Source const&
    >::type argument_type ;

    static inline source_type nearbyint(argument_type s, bool& is_ok) BOOST_NOEXCEPT {
        const source_type near_int = Rounder::nearbyint(s);
        if (near_int && is_ok) {
            const source_type orig_div_round = s / near_int;
            const source_type eps = std::numeric_limits<source_type>::epsilon();

            is_ok = !((orig_div_round > 1 ? orig_div_round - 1 : 1 - orig_div_round) > eps);
        }

        return s;
    }

    typedef typename Rounder::round_style round_style;
};

template <typename Base, class Source>
struct fake_precision_loss: public Base
{
    typedef Source source_type ;
    typedef BOOST_DEDUCED_TYPENAME mpl::if_<
        boost::is_arithmetic<Source>, Source, Source const&
    >::type argument_type ;

    static inline source_type nearbyint(argument_type s, bool& /*is_ok*/) BOOST_NOEXCEPT {
        return s;
    }
};

struct nothrow_overflow_handler
{
    inline bool operator() ( boost::numeric::range_check_result r ) const BOOST_NOEXCEPT {
        return (r == boost::numeric::cInRange);
    }
};

template <typename Target, typename Source>
inline bool noexcept_numeric_convert(const Source& arg, Target& result) BOOST_NOEXCEPT {
    typedef boost::numeric::converter<
            Target,
            Source,
            boost::numeric::conversion_traits<Target, Source >,
            nothrow_overflow_handler,
            detect_precision_loss<Source >
    > converter_orig_t;

    typedef BOOST_DEDUCED_TYPENAME boost::mpl::if_c<
        boost::is_base_of< detect_precision_loss<Source >, converter_orig_t >::value,
        converter_orig_t,
        fake_precision_loss<converter_orig_t, Source>
    >::type converter_t;

    bool res = nothrow_overflow_handler()(converter_t::out_of_range(arg));
    result = converter_t::low_level_convert(converter_t::nearbyint(arg, res));
    return res;
}

template <typename Target, typename Source>
struct lexical_cast_dynamic_num_not_ignoring_minus
{
    static inline bool try_convert(const Source &arg, Target& result) BOOST_NOEXCEPT {
        return noexcept_numeric_convert<Target, Source >(arg, result);
    }
};

template <typename Target, typename Source>
struct lexical_cast_dynamic_num_ignoring_minus
{
    static inline bool try_convert(const Source &arg, Target& result) BOOST_NOEXCEPT {
        typedef BOOST_DEDUCED_TYPENAME boost::mpl::eval_if_c<
                boost::is_float<Source>::value,
                boost::mpl::identity<Source>,
                boost::make_unsigned<Source>
        >::type usource_t;

        if (arg < 0) {
            const bool res = noexcept_numeric_convert<Target, usource_t>(0u - arg, result);
            result = static_cast<Target>(0u - result);
            return res;
        } else {
            return noexcept_numeric_convert<Target, usource_t>(arg, result);
        }
    }
};

/*
 * lexical_cast_dynamic_num follows the rules:
 * 1) If Source can be converted to Target without precision loss and
 * without overflows, then assign Source to Target and return
 *
 * 2) If Source is less than 0 and Target is an unsigned integer,
 * then negate Source, check the requirements of rule 1) and if
 * successful, assign static_casted Source to Target and return
 *
 * 3) Otherwise throw a bad_lexical_cast exception
 *
 *
 * Rule 2) required because boost::lexical_cast has the behavior of
 * stringstream, which uses the rules of scanf for conversions. And
 * in the C99 standard for unsigned input value minus sign is
 * optional, so if a negative number is read, no errors will arise
 * and the result will be the two's complement.
 */
template <typename Target, typename Source>
struct dynamic_num_converter_impl
{
    static inline bool try_convert(const Source &arg, Target& result) BOOST_NOEXCEPT {
        typedef BOOST_DEDUCED_TYPENAME boost::mpl::if_c<
            boost::is_unsigned<Target>::value &&
            (boost::is_signed<Source>::value || boost::is_float<Source>::value) &&
            !(boost::is_same<Source, bool>::value) &&
            !(boost::is_same<Target, bool>::value),
            lexical_cast_dynamic_num_ignoring_minus<Target, Source>,
            lexical_cast_dynamic_num_not_ignoring_minus<Target, Source>
        >::type caster_type;

        return caster_type::try_convert(arg, result);
    }
};

}} // namespace boost::detail

#endif // BOOST_LEXICAL_CAST_DETAIL_CONVERTER_NUMERIC_HPP


code:
// Copyright Kevlin Henney, 2000-2005.
// Copyright Alexander Nasonov, 2006-2010.
// Copyright Antony Polukhin, 2011-2014.
//
// Distributed under 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)
//
// what:  lexical_cast custom keyword cast
// who:   contributed by Kevlin Henney,
//        enhanced with contributions from Terje Slettebo,
//        with additional fixes and suggestions from Gennaro Prota,
//        Beman Dawes, Dave Abrahams, Daryle Walker, Peter Dimov,
//        Alexander Nasonov, Antony Polukhin, Justin Viiret, Michael Hofmann,
//        Cheng Yang, Matthew Bradbury, David W. Birdsall, Pavel Korzh and other Boosters
// when:  November 2000, March 2003, June 2005, June 2006, March 2011 - 2014

#ifndef BOOST_LEXICAL_CAST_DETAIL_INF_NAN_HPP
#define BOOST_LEXICAL_CAST_DETAIL_INF_NAN_HPP

#include <boost/config.hpp>
#ifdef BOOST_HAS_PRAGMA_ONCE
#   pragma once
#endif

#if defined(BOOST_NO_STRINGSTREAM) || defined(BOOST_NO_STD_WSTRING)
#define BOOST_LCAST_NO_WCHAR_T
#endif

#include <cstddef>
#include <cstring>
#include <boost/limits.hpp>
#include <boost/detail/workaround.hpp>
#include <boost/math/special_functions/sign.hpp>
#include <boost/math/special_functions/fpclassify.hpp>

#include <boost/lexical_cast/detail/lcast_char_constants.hpp>

namespace boost {
    namespace detail
    {
        template <class CharT>
        bool lc_iequal(const CharT* val, const CharT* lcase, const CharT* ucase, unsigned int len) BOOST_NOEXCEPT {
            for( unsigned int i=0; i < len; ++i ) {
                if ( val[i] != lcase[i] && val[i] != ucase[i] ) return false;
            }

            return true;
        }

        /* Returns true and sets the correct value if found NaN or Inf. */
        template <class CharT, class T>
        inline bool parse_inf_nan_impl(const CharT* begin, const CharT* end, T& value
            , const CharT* lc_NAN, const CharT* lc_nan
            , const CharT* lc_INFINITY, const CharT* lc_infinity
            , const CharT opening_brace, const CharT closing_brace) BOOST_NOEXCEPT
        {
            using namespace std;
            if (begin == end) return false;
            const CharT minus = lcast_char_constants<CharT>::minus;
            const CharT plus = lcast_char_constants<CharT>::plus;
            const int inifinity_size = 8; // == sizeof("infinity") - 1

            /* Parsing +/- */
            bool const has_minus = (*begin == minus);
            if (has_minus || *begin == plus) {
                ++ begin;
            }

            if (end - begin < 3) return false;
            if (lc_iequal(begin, lc_nan, lc_NAN, 3)) {
                begin += 3;
                if (end != begin) {
                    /* It is 'nan(...)' or some bad input*/

                    if (end - begin < 2) return false; // bad input
                    -- end;
                    if (*begin != opening_brace || *end != closing_brace) return false; // bad input
                }

                if( !has_minus ) value = std::numeric_limits<T>::quiet_NaN();
                else value = (boost::math::changesign) (std::numeric_limits<T>::quiet_NaN());
                return true;
            } else if (
                ( /* 'INF' or 'inf' */
                  end - begin == 3      // 3 == sizeof('inf') - 1
                  && lc_iequal(begin, lc_infinity, lc_INFINITY, 3)
                )
                ||
                ( /* 'INFINITY' or 'infinity' */
                  end - begin == inifinity_size
                  && lc_iequal(begin, lc_infinity, lc_INFINITY, inifinity_size)
                )
             )
            {
                if( !has_minus ) value = std::numeric_limits<T>::infinity();
                else value = (boost::math::changesign) (std::numeric_limits<T>::infinity());
                return true;
            }

            return false;
        }

        template <class CharT, class T>
        bool put_inf_nan_impl(CharT* begin, CharT*& end, const T& value
                         , const CharT* lc_nan
                         , const CharT* lc_infinity) BOOST_NOEXCEPT
        {
            using namespace std;
            const CharT minus = lcast_char_constants<CharT>::minus;
            if ((boost::math::isnan)(value)) {
                if ((boost::math::signbit)(value)) {
                    *begin = minus;
                    ++ begin;
                }

                memcpy(begin, lc_nan, 3 * sizeof(CharT));
                end = begin + 3;
                return true;
            } else if ((boost::math::isinf)(value)) {
                if ((boost::math::signbit)(value)) {
                    *begin = minus;
                    ++ begin;
                }

                memcpy(begin, lc_infinity, 3 * sizeof(CharT));
                end = begin + 3;
                return true;
            }

            return false;
        }

#ifndef BOOST_LCAST_NO_WCHAR_T
        template <class T>
        bool parse_inf_nan(const wchar_t* begin, const wchar_t* end, T& value) BOOST_NOEXCEPT {
            return parse_inf_nan_impl(begin, end, value
                               , L"NAN", L"nan"
                               , L"INFINITY", L"infinity"
                               , L'(', L')');
        }

        template <class T>
        bool put_inf_nan(wchar_t* begin, wchar_t*& end, const T& value) BOOST_NOEXCEPT {
            return put_inf_nan_impl(begin, end, value, L"nan", L"infinity");
        }

#endif
#if !defined(BOOST_NO_CXX11_CHAR16_T) && !defined(BOOST_NO_CXX11_UNICODE_LITERALS)
        template <class T>
        bool parse_inf_nan(const char16_t* begin, const char16_t* end, T& value) BOOST_NOEXCEPT {
            return parse_inf_nan_impl(begin, end, value
                               , u"NAN", u"nan"
                               , u"INFINITY", u"infinity"
                               , u'(', u')');
        }

        template <class T>
        bool put_inf_nan(char16_t* begin, char16_t*& end, const T& value) BOOST_NOEXCEPT {
            return put_inf_nan_impl(begin, end, value, u"nan", u"infinity");
        }
#endif
#if !defined(BOOST_NO_CXX11_CHAR32_T) && !defined(BOOST_NO_CXX11_UNICODE_LITERALS)
        template <class T>
        bool parse_inf_nan(const char32_t* begin, const char32_t* end, T& value) BOOST_NOEXCEPT {
            return parse_inf_nan_impl(begin, end, value
                               , U"NAN", U"nan"
                               , U"INFINITY", U"infinity"
                               , U'(', U')');
        }

        template <class T>
        bool put_inf_nan(char32_t* begin, char32_t*& end, const T& value) BOOST_NOEXCEPT {
            return put_inf_nan_impl(begin, end, value, U"nan", U"infinity");
        }
#endif

        template <class CharT, class T>
        bool parse_inf_nan(const CharT* begin, const CharT* end, T& value) BOOST_NOEXCEPT {
            return parse_inf_nan_impl(begin, end, value
                               , "NAN", "nan"
                               , "INFINITY", "infinity"
                               , '(', ')');
        }

        template <class CharT, class T>
        bool put_inf_nan(CharT* begin, CharT*& end, const T& value) BOOST_NOEXCEPT {
            return put_inf_nan_impl(begin, end, value, "nan", "infinity");
        }
    }
} // namespace boost

#undef BOOST_LCAST_NO_WCHAR_T

#endif // BOOST_LEXICAL_CAST_DETAIL_INF_NAN_HPP


code:
// Copyright Kevlin Henney, 2000-2005.
// Copyright Alexander Nasonov, 2006-2010.
// Copyright Antony Polukhin, 2011-2014.
//
// Distributed under 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)
//
// what:  lexical_cast custom keyword cast
// who:   contributed by Kevlin Henney,
//        enhanced with contributions from Terje Slettebo,
//        with additional fixes and suggestions from Gennaro Prota,
//        Beman Dawes, Dave Abrahams, Daryle Walker, Peter Dimov,
//        Alexander Nasonov, Antony Polukhin, Justin Viiret, Michael Hofmann,
//        Cheng Yang, Matthew Bradbury, David W. Birdsall, Pavel Korzh and other Boosters
// when:  November 2000, March 2003, June 2005, June 2006, March 2011 - 2014

#ifndef BOOST_LEXICAL_CAST_DETAIL_IS_CHARACTER_HPP
#define BOOST_LEXICAL_CAST_DETAIL_IS_CHARACTER_HPP

#include <boost/config.hpp>
#ifdef BOOST_HAS_PRAGMA_ONCE
#   pragma once
#endif

#include <boost/mpl/bool.hpp>
#include <boost/type_traits/is_same.hpp>

namespace boost {

    namespace detail // is_character<...>
    {
        // returns true, if T is one of the character types
        template < typename T >
        struct is_character
        {
            typedef BOOST_DEDUCED_TYPENAME boost::mpl::bool_<
                    boost::is_same< T, char >::value ||
                    #if !defined(BOOST_NO_STRINGSTREAM) && !defined(BOOST_NO_STD_WSTRING)
                        boost::is_same< T, wchar_t >::value ||
                    #endif
                    #ifndef BOOST_NO_CXX11_CHAR16_T
                        boost::is_same< T, char16_t >::value ||
                    #endif
                    #ifndef BOOST_NO_CXX11_CHAR32_T
                        boost::is_same< T, char32_t >::value ||
                    #endif
                   	boost::is_same< T, unsigned char >::value ||
                   	boost::is_same< T, signed char >::value
            > type;

            BOOST_STATIC_CONSTANT(bool, value = (type::value) );
        };
    }
}

#endif // BOOST_LEXICAL_CAST_DETAIL_IS_CHARACTER_HPP


code:
// Copyright Kevlin Henney, 2000-2005.
// Copyright Alexander Nasonov, 2006-2010.
// Copyright Antony Polukhin, 2011-2014.
//
// Distributed under 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)
//
// what:  lexical_cast custom keyword cast
// who:   contributed by Kevlin Henney,
//        enhanced with contributions from Terje Slettebo,
//        with additional fixes and suggestions from Gennaro Prota,
//        Beman Dawes, Dave Abrahams, Daryle Walker, Peter Dimov,
//        Alexander Nasonov, Antony Polukhin, Justin Viiret, Michael Hofmann,
//        Cheng Yang, Matthew Bradbury, David W. Birdsall, Pavel Korzh and other Boosters
// when:  November 2000, March 2003, June 2005, June 2006, March 2011 - 2014

#ifndef BOOST_LEXICAL_CAST_DETAIL_LCAST_CHAR_CONSTANTS_HPP
#define BOOST_LEXICAL_CAST_DETAIL_LCAST_CHAR_CONSTANTS_HPP

#include <boost/config.hpp>
#ifdef BOOST_HAS_PRAGMA_ONCE
#   pragma once
#endif

namespace boost
{
    namespace detail // '0', '-', '+', 'e', 'E' and '.' constants
    {
        template < typename Char >
        struct lcast_char_constants {
            // We check in tests assumption that static casted character is
            // equal to correctly written C++ literal: U'0' == static_cast<char32_t>('0')
            BOOST_STATIC_CONSTANT(Char, zero  = static_cast<Char>('0'));
            BOOST_STATIC_CONSTANT(Char, minus = static_cast<Char>('-'));
            BOOST_STATIC_CONSTANT(Char, plus = static_cast<Char>('+'));
            BOOST_STATIC_CONSTANT(Char, lowercase_e = static_cast<Char>('e'));
            BOOST_STATIC_CONSTANT(Char, capital_e = static_cast<Char>('E'));
            BOOST_STATIC_CONSTANT(Char, c_decimal_separator = static_cast<Char>('.'));
        };
    }
} // namespace boost

#endif // BOOST_LEXICAL_CAST_DETAIL_LCAST_CHAR_CONSTANTS_HPP