问：使用std :: ctype widen（）将std :: string转换为std :: wstring [英] Q: Convert std::string to std::wstring using std::ctype widen()
问题描述
大家好，
我做了一些小作业（我已经阅读了类似于PJ的回复
Plauger和Dietmar Kuehl） ，并希望与集团核实。以下
是我的表现（Stroustrup的附录D建议不会在Microsoft VC ++ 6.0中编译
）。
我的问题是参考MultiByte字符集。这段代码
会按预期执行吗？我知道每个问题都有一个简单的，优雅的解决方案是错误的。
我一般使用美国英语或Unicode，所以我没有遇到过很多
其他人可能看到的问题（使用std :: string的多字节字符）。我有
验证它适用于Hello World样本。
Jeff
Jeffrey Walton
std :: string s =" Hello World";
std :: ctype< wchar_tct;
std :: wstring ws;
for（std :: string :: const_iterator it = s.begin（）; it！= s.end（）;
it ++）
{
ws + = ct.widen（* it）;
}
// http://www.research.att.com/~bs/3rd_loc.pdf
//由Bjourne自己...
//上述参考文件第28页
//或
// C ++编程语言，特别版
// D.4.2.2节，第895页（完整手册）
//
// const std :: locale& loc = s.getloc（）;
// wchar_t w = std :: use_facet< std :: ctype< char（loc）。widen（c）;
//在Microsft的环境中无法编译...
// getloc（）不是std :: basic_string<的成员......
//
// Dietmar Kuehl代码
//无法在VC ++ 6.0中编译< br $>
//
// std :: wstring to_wide_string（std :: string const& source）{
// typedef std :: ctype< wchar_tCT;
// std :: wstring rc;
// rc.resize（source.size（））;
// CT常量和放大器; ct = std :: use_facet< CT>（std :: locale（））;
// ct.widen（source.data（），source.data（）+ source.size（），
rc.data（））;
//返回rc;
Hi All,
I''ve done a little homework (I''ve read responses to similar from P.J.
Plauger and Dietmar Kuehl), and wanted to verify with the Group. Below
is what I am performing (Stroustrup''s Appendix D recommendation won''t
compile in Microsoft VC++ 6.0).
My question is in reference to MultiByte Character Sets. Will this code
perform as expected? I understand every problem has a simple and
elegant solution that is wrong.
I generally use US English or Unicode, so I don''t encounter a lot of
issues others may see (a multibyte character using std::string). I have
verified it works with a Hello World sample.
Jeff
Jeffrey Walton
std::string s = "Hello World";
std::ctype<wchar_tct;
std::wstring ws;
for( std::string::const_iterator it = s.begin(); it != s.end();
it++ )
{
ws += ct.widen( *it );
}
// http://www.research.att.com/~bs/3rd_loc.pdf
// by Bjourne himself...
// page 28 of the above reference
// or
// The C++ Programming Language, Special Edition
// Section D.4.2.2, p 895 (Full Manual)
//
// const std::locale& loc = s.getloc();
// wchar_t w = std::use_facet< std::ctype<char(loc).widen(c);
// does not compile in Microsft''s environment...
// getloc() is not a member of std::basic_string< ... ...
//
// Dietmar Kuehl code
// Does not compile in VC++ 6.0
//
// std::wstring to_wide_string(std::string const& source) {
// typedef std::ctype<wchar_tCT;
// std::wstring rc;
// rc.resize(source.size());
// CT const& ct = std::use_facet<CT>(std::locale());
// ct.widen(source.data(), source.data() + source.size(),
rc.data());
// return rc;
推荐答案
Jeffrey Walton写道：
Jeffrey Walton wrote:
大家好，
我做了一点功课（我''我已经阅读了PJ的相似回复
Plauger和Dietmar Kuehl），并想与集团核实。
SNIP ......
Jeff
Jeffrey Walton
std :: string s =" Hello World";
std :: ctype< wchar_tct;
std :: wstring ws;
for（std :: string :: const_iterator it = s.begin（）;它！= s.end（）;
它++）
{
ws + = ct.widen（* it）;
}
// HTTP：//www.resear ch.att.com/~bs/3rd_loc.pdf
// Bjourne本人......
//上述参考文献第28页
//或
// C ++编程语言，特别版
// D.4.2.2节，第895页（完整手册）
SNIP代码......
SNIP代码...
Hi All,
I''ve done a little homework (I''ve read responses to similar from P.J.
Plauger and Dietmar Kuehl), and wanted to verify with the Group.
SNIP...
Jeff
Jeffrey Walton
std::string s = "Hello World";
std::ctype<wchar_tct;
std::wstring ws;
for( std::string::const_iterator it = s.begin(); it != s.end();
it++ )
{
ws += ct.widen( *it );
}
// http://www.research.att.com/~bs/3rd_loc.pdf
// by Bjourne himself...
// page 28 of the above reference
// or
// The C++ Programming Language, Special Edition
// Section D.4.2.2, p 895 (Full Manual)
SNIP Code...
SNIP Code...
之前我因为没有使用std :: codecvt而受到攻击，Stroustrup声明
（D.4.6字符代码转换，第925页）：
codecvt facet提供不同字符集之间的转换
当一个角色在一个流缓冲区和外部
存储之间移动时......
Jeff
Jeffrey Walton
Before I get flamed for not using std::codecvt, Stroustrup states
(D.4.6 Character Code Conversion, p 925):
The codecvt facet provides conversion between different character sets
when a character is moved between a stream buffer and external
storage...
Jeff
Jeffrey Walton
Jeffrey Walton写道：
Jeffrey Walton wrote:
大家好，
我做了一些小作业（我已经阅读了类似于PJ的回复
Plauger和Dietmar Kuehl），以及想验证群组。以下
是我正在执行的（Stroustrup的附录D建议不会在Microsoft VC ++ 6.0中编译
）。
Hi All,
I''ve done a little homework (I''ve read responses to similar from P.J.
Plauger and Dietmar Kuehl), and wanted to verify with the Group. Below
is what I am performing (Stroustrup''s Appendix D recommendation won''t
compile in Microsoft VC++ 6.0).
< ...>
<...>
// Dietmar Kuehl代码
//无法在VC ++ 6.0中编译
// Dietmar Kuehl code
// Does not compile in VC++ 6.0
< ..>
不幸的是问题可能是VC ++ 6.0，而不是源代码。
省去使用VC ++ 6的痛苦并获得一个副本ov VC7.1
或VC8.0或gcc。，
通过这样做，你将开辟一个全新的世界...
问候
Andy Little
<..>
Unfortunately the problem is probably VC++6.0 , not the source code.
Save yourself the pain of using VC++6 and get hold of a copy ov VC7.1
or VC8.0 or gcc.,
By doing so you will open up a whole new world...
regards
Andy Little
kwikius写道：
kwikius wrote:
Jeffrey Walton写道：
Jeffrey Walton wrote:
大家好，
我做了一些功课（我已经阅读了类似的回复来自PJ
Plauger和Dietmar Kuehl），并希望与集团核实。以下
是我正在执行的（Stroustrup的附录D建议不会在Microsoft VC ++ 6.0中编译
）。
Hi All,
I''ve done a little homework (I''ve read responses to similar from P.J.
Plauger and Dietmar Kuehl), and wanted to verify with the Group. Below
is what I am performing (Stroustrup''s Appendix D recommendation won''t
compile in Microsoft VC++ 6.0).
< ...>
<...>
// Dietmar Kuehl代码
//无法在VC ++ 6.0中编译
// Dietmar Kuehl code
// Does not compile in VC++ 6.0
< ..>
不幸的是问题可能是VC ++ 6.0，不是源代码。
SNIP ...
问候
Andy Little
<..>
Unfortunately the problem is probably VC++6.0 , not the source code.
SNIP ...
regards
Andy Little
嗨Andy，
Hi Andy,
省去使用VC ++ 6的痛苦并抓住副本ov VC7.1
或VC8.0或gcc。，
Save yourself the pain of using VC++6 and get hold of a copy ov VC7.1
or VC8.0 or gcc.,
不可行......
我甚至无法编译以下内容（来自Stroustrup）：
wchar_t wc = std :: use_facet< std :: ctype< wchar_t
（std :: wcout.getloc（））。widen（''e''）;
我想我是如果我不能得到关于走路的信息，那就去吧。
std :: string。由于我的示例编译（并使用Ch = widen（c）），它将按预期执行。
Stroustrup（第D.4.5节，第。923）：
呼叫加宽（c）将字符c转换为相应的Ch
值。如果Ch'的字符集提供了与c对应的几个字符
，则该标准指定实施合理的
转换。使用。
Jeff
Jeffrey Walton
Not feasible...
I can''t even get the following to compile (from Stroustrup):
wchar_t wc = std::use_facet< std::ctype<wchar_t
(std::wcout.getloc()).widen(''e'') ;
I think I am going to punt if I can''t get input on walking the
std::string. Since my example compiles (and uses Ch = widen( c ) ), it
should perform as expected.
Stroustrup again (Section D.4.5, p. 923):
A call widen(c) transforms the character c into its corresponding Ch
value. If Ch''s character set provides several characters
corresponding to c, the standard specifies that "the implest reasonable
transformation" be used.
Jeff
Jeffrey Walton
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