• <ins id="pjuwb"></ins>
    <blockquote id="pjuwb"><pre id="pjuwb"></pre></blockquote>
    <noscript id="pjuwb"></noscript>
          <sup id="pjuwb"><pre id="pjuwb"></pre></sup>
            <dd id="pjuwb"></dd>
            <abbr id="pjuwb"></abbr>

            linux&c++ R&D

            programing is a pleasure!

            Using std::basic_string the extensible way

            Problem:
            Using std::basic_string the extensible way
            I'm writing a class that contains a string. But I decided to make it
            more extensible and turn it into a class template:
            template<typename CharT>
            class My
            {
                 std::basic_string<CharT> text;
            };

            How do I operate on such a string, so that it will work for any valid
            instantiation of basic_string? For example, I'd like to append some text
            to the end of the string or check if the first letter is lowercase.
            Currently I'm doing:
                 text += "some other text";
            For wstring I should probably do:
                 test += L"some other text";
            How do I do it in a generic way?
            Solution:
            That depends on the meaning of these literals.
            Are these only some selected literals of the
            corresponding character type with a special
            meaning? If so, than a character-depending
            policy/traits class would be reasonable, which
            would be explicitely specialized for the corresponding
            value, e.g.
            template <typename CharT> 
            class MyTraits; 
            template 
            <> 
            struct MyTraits
            <char> 
              
            static const char* append() 
                
            return "some other text"
              }

            }

            template 
            <> 
            struct MyTraits
            <wchar_t> 
              
            static const wchar_t* append() 
                
            return L"some other text"
              }
             
            }

            template
            <typename CharT> 
            class My 

               std::basic_string
            <CharT> text; 
               typedef MyTraits
            <CharT> Traits; 
               
            void foo() 
                  text 
            += Traits::append(); 
               }
             
            }


            Otherwise you could only declare the member
            functions in the My class template and explicitely
            specialize them for the corresponding character
            type:
            template<typename CharT> 
            class My 

               std::basic_string
            <CharT> text; 
            public
               
            void foo(); // Only declared, not defined 
            }

            template
            <> 
            void My<char>::foo() 
              text 
            += "some other text"
            }
             
            template
            <> 
            void My<wchar_t>::foo() 
              text 
            += L"some other text"
            }
             

            In both cases some preprocessor magic
            can help reducing the redundancies.
            ----------------------------------------------------------------------------
            How about writing a helper function to convert a narrow string literal
            to an arbitrary basic_string<T>: 
               // A template to 'widen' a string literal 
               
            template < class CharT > 
               std::basic_string
            <CharT> widen( char const* str ) 
                 std::basic_stringstream
            < CharT > s; 
                 s 
            << str; return s.str(); 
               }
             
            Then you can 
            do 
               test 
            += widen<char>"foo bar" ); 
            or 
               test 
            += widen<wchar_t>"foo bar" ); 

            as appropriate.
            You could even make it a constructor, but it's probably best to make it
            explicit in the code when you want this widening.

            posted on 2007-04-25 23:39 丑石 閱讀(800) 評論(0)  編輯 收藏 引用 所屬分類: C++ problem and solution

            My Links

            Blog Stats

            News

            常用鏈接

            留言簿(1)

            隨筆分類(13)

            隨筆檔案(17)

            文章檔案(1)

            相冊

            收藏夾(1)

            Friends' blog

            useful sites

            搜索

            積分與排名

            最新評論

            閱讀排行榜

            評論排行榜

            久久er国产精品免费观看8| 久久久久人妻一区二区三区| 久久久久无码精品国产| 国产成人久久激情91| 久久青青国产| 久久久一本精品99久久精品88| 色88久久久久高潮综合影院| 免费精品99久久国产综合精品| 久久综合色之久久综合| www性久久久com| 香蕉久久夜色精品国产尤物| 国产精品久久久久影院嫩草| 波多野结衣久久| 久久精品国产色蜜蜜麻豆| 久久亚洲美女精品国产精品| 日本精品一区二区久久久| 99热成人精品热久久669| 亚洲中文字幕无码久久2017| 久久成人18免费网站| 亚洲午夜精品久久久久久人妖| 国内精品综合久久久40p| 蜜臀久久99精品久久久久久| 久久精品国产精品青草| 国产亚洲综合久久系列| 亚洲精品乱码久久久久久 | 久久久青草青青国产亚洲免观| 久久99久久99精品免视看动漫| 亚洲国产视频久久| 日韩电影久久久被窝网| 久久激情亚洲精品无码?V| 91精品国产91久久久久久| 97久久综合精品久久久综合| 少妇精品久久久一区二区三区| 久久AV高潮AV无码AV| 久久精品国产清自在天天线| 思思久久99热只有频精品66| 久久男人中文字幕资源站| 亚洲国产成人久久笫一页| 亚洲伊人久久成综合人影院 | 精品欧美一区二区三区久久久| 久久综合综合久久97色|