Обертка над boost::lexical_cast для работы с unsigned типами - C++ - Ответ 8694366

namespace detail
{
    struct string_cast_impl
    {
        template<typename TargetType, typename Str> static
        typename std::enable_if<std::is_unsigned<TargetType>::value, TargetType>::type
        cast(const Str& source)
        {
            if (!source.empty() && source[0] == '-'){
                TargetType result = boost::lexical_cast<TargetType>(source) ;
                return (result!=0) ? throw boost::bad_lexical_cast(),TargetType(0) : result  ;
            }
            return boost::lexical_cast<TargetType>(source);
        }
 
 
        template<typename TargetType, typename Str> static
        typename std::enable_if<!std::is_unsigned<TargetType>::value, TargetType>::type
        cast(const Str& source)
        {
            return boost::lexical_cast<TargetType>(source) ;
        }
    };
}//end of detail
 
 
template<typename TargetType, typename StringType>
std::enable_if_t<
    !std::is_same<
        std::decay_t<StringType>,
        Glib::ustring
    >::value,
    std::decay_t<TargetType>
>
string_cast(StringType&& source)
{
    using CharT =
        typename std::remove_const<
            typename std::remove_reference<decltype(source[0])>::type
        >::type;
 
    using DecayType = typename std::decay<TargetType>::type ;
 
    //std::string str(std::forward<StringType>(source)) ;
 
    std::basic_string<CharT> str(std::forward<StringType>(source)) ;
 
    boost::trim(str) ;
    return detail::string_cast_impl::cast<DecayType>(str) ;
 
}
 
 
template<typename TargetType, typename StringType>
std::enable_if_t<
    std::is_same<
        std::decay_t<StringType>,
        Glib::ustring
    >::value,
    std::decay_t<TargetType>
>
string_cast(StringType&& source)
{
    using DecayType = typename std::decay<TargetType>::type ;
    std::string str(std::forward<StringType>(source)) ;
    boost::trim(str) ;
    return detail::string_cast_impl::cast<DecayType>(str) ;
}