人们发现在 C++ 中将字符串转换为小写/大写的最佳方法是什么？
由于 C++ 不是纯英语的编程语言，这个问题变得复杂了。有没有好的多语言方法？
Adam
问问题
23042 次
10 回答
30
#include <algorithm>
std::string data = "Abc";
std::transform(data.begin(), data.end(), data.begin(), ::toupper);
http://notfaq.wordpress.com/2007/08/04/cc-convert-string-to-upperlower-case/
此外，常见字符串方法的 CodeProject 文章：http: //www.codeproject.com/KB/stl/STL_string_util.aspx
于 2008-08-14T18:53:43.530 回答
20
> std::string data = “Abc”;
> std::transform(data.begin(), data.end(), data.begin(), ::toupper);
这将起作用，但这将使用标准的“C”语言环境。如果您需要为其他语言环境获取 tolower，则可以使用构面。上面使用构面的代码将是：
locale loc("");
const ctype<char>& ct = use_facet<ctype<char> >(loc);
transform(str.begin(), str.end(), std::bind1st(std::mem_fun(&ctype<char>::tolower), &ct));
于 2008-08-21T23:05:23.650 回答
7
对于希望使用 Nic Strong 答案的复制粘贴者，请注意“use_factet”中的拼写错误以及 std::transform 缺少的第三个参数：
locale loc("");
const ctype<char>& ct = use_factet<ctype<char> >(loc);
transform(str.begin(), str.end(), std::bind1st(std::mem_fun(&ctype<char>::tolower), &ct));
应该
locale loc("");
const ctype<char>& ct = use_facet<ctype<char> >(loc);
transform(str.begin(), str.end(), str.begin(), std::bind1st(std::mem_fun(&ctype<char>::tolower), &ct));
于 2009-11-12T19:02:13.187 回答
4
您还应该查看这个问题。基本上问题在于标准 C/C++ 库不是为处理 Unicode 数据而构建的，因此您必须查看其他库。
这可能会随着 C++ 标准的更新而改变。我知道 Borland 的下一个编译器 (CodeGear) 将支持 Unicode，我猜微软的 C++ 编译器将支持或已经支持支持 Unicode 的字符串库。
于 2008-08-16T20:25:51.290 回答
2
正如 Darren 告诉你的，最简单的方法是使用 std::transform。
但请注意，在某些语言中，例如德语，小写和大写之间并不总是一对一的映射。“esset”小写字符（看起来像希腊字符 beta）被转换为大写的“SS”。
于 2008-08-17T13:30:59.770 回答
2
如果你有 Boost，那么它有最简单的方法。查看Boost 字符串算法中的 to_upper()/to_lower()。
于 2010-12-02T14:40:00.760 回答
1
我找到了一种转换 unicode（和多语言）字符大小写的方法，但是您需要知道/找到（以某种方式）字符的语言环境：
#include <locale.h>
_locale_t locale = _create_locale(LC_CTYPE, "Greek");
AfxMessageBox((CString)""+(TCHAR)_totupper_l(_T('α'), locale));
_free_locale(locale);
我还没有找到一种方法来做到这一点......我有人知道怎么做，让我知道。
将语言环境设置为 NULL 不起作用...
于 2013-03-01T05:34:06.827 回答
1
The VCLhas a SysUtils.hppwhich has LowerCase(unicodeStringVar)and UpperCase(unicodeStringVar)which may work for you。我在 C++ Builder 2009 中使用它。
于 2014-01-27T17:40:20.057 回答
0
史蒂夫说的是对的，但我想如果你的代码必须支持多种语言，你可以有一个工厂方法，它封装了一组基于该语言执行相关 toUpper 或 toLower 的方法。
于 2008-08-26T18:58:13.440 回答
0
基于Kyle_the_hacker 的----->回答我的额外内容。
Ubuntu
在终端列出所有语言环境
locale -a
安装所有语言环境
sudo apt-get install -y locales locales-all
编译 main.cpp
$ g++ main.cpp
运行编译好的程序
$ ./a.out
结果
Zoë Saldaña played in La maldición del padre Cardona. ëèñ αω óóChloë
Zoë Saldaña played in La maldición del padre Cardona. ëèñ αω óóChloë
ZOË SALDAÑA PLAYED IN LA MALDICIÓN DEL PADRE CARDONA. ËÈÑ ΑΩ ÓÓCHLOË
ZOË SALDAÑA PLAYED IN LA MALDICIÓN DEL PADRE CARDONA. ËÈÑ ΑΩ ÓÓCHLOË
zoë saldaña played in la maldición del padre cardona. ëèñ αω óóchloë
zoë saldaña played in la maldición del padre cardona. ëèñ αω óóchloë
视窗
在 cmd 中运行 VCVARS 开发者工具
"C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Auxiliary\Build\vcvars64.bat"
编译 main.cpp
> cl /EHa main.cpp /D "_DEBUG" /D "_CONSOLE" /D "_UNICODE" /D "UNICODE" /std:c++17 /DYNAMICBASE "kernel32.lib" "user32.lib" "gdi32.lib" "winspool.lib" "comdlg32.lib" "advapi32.lib" "shell32.lib" "ole32.lib" "oleaut32.lib" "uuid.lib" "odbc32.lib" "odbccp32.lib" /MTd
Compilador de optimización de C/C++ de Microsoft (R) versión 19.27.29111 para x64
(C) Microsoft Corporation. Todos los derechos reservados.
main.cpp
Microsoft (R) Incremental Linker Version 14.27.29111.0
Copyright (C) Microsoft Corporation. All rights reserved.
/out:main.exe
main.obj
kernel32.lib
user32.lib
gdi32.lib
winspool.lib
comdlg32.lib
advapi32.lib
shell32.lib
ole32.lib
oleaut32.lib
uuid.lib
odbc32.lib
odbccp32.lib
运行 main.exe
>main.exe
结果
Zoë Saldaña played in La maldición del padre Cardona. ëèñ αω óóChloë
Zoë Saldaña played in La maldición del padre Cardona. ëèñ αω óóChloë
ZOË SALDAÑA PLAYED IN LA MALDICIÓN DEL PADRE CARDONA. ËÈÑ ΑΩ ÓÓCHLOË
ZOË SALDAÑA PLAYED IN LA MALDICIÓN DEL PADRE CARDONA. ËÈÑ ΑΩ ÓÓCHLOË
zoë saldaña played in la maldición del padre cardona. ëèñ αω óóchloë
zoë saldaña played in la maldición del padre cardona. ëèñ αω óóchloë
代码 - main.cpp
此代码仅在 Windows x64 和 Ubuntu Linux x64 上进行了测试。
/*
* Filename: c:\Users\x\Cpp\main.cpp
* Path: c:\Users\x\Cpp
* Filename: /home/x/Cpp/main.cpp
* Path: /home/x/Cpp
* Created Date: Saturday, October 17th 2020, 10:43:31 pm
* Author: Joma
*
* No Copyright 2020
*/
#include <iostream>
#include <set>
#include <string>
#include <locale>
// WINDOWS
#if (_WIN32)
#include <Windows.h>
#include <conio.h>
#define WINDOWS_PLATFORM 1
#define DLLCALL STDCALL
#define DLLIMPORT _declspec(dllimport)
#define DLLEXPORT _declspec(dllexport)
#define DLLPRIVATE
#define NOMINMAX
//EMSCRIPTEN
#elif defined(__EMSCRIPTEN__)
#include <emscripten/emscripten.h>
#include <emscripten/bind.h>
#include <unistd.h>
#include <termios.h>
#define EMSCRIPTEN_PLATFORM 1
#define DLLCALL
#define DLLIMPORT
#define DLLEXPORT __attribute__((visibility("default")))
#define DLLPRIVATE __attribute__((visibility("hidden")))
// LINUX - Ubuntu, Fedora, , Centos, Debian, RedHat
#elif (__LINUX__ || __gnu_linux__ || __linux__ || __linux || linux)
#define LINUX_PLATFORM 1
#include <unistd.h>
#include <termios.h>
#define DLLCALL CDECL
#define DLLIMPORT
#define DLLEXPORT __attribute__((visibility("default")))
#define DLLPRIVATE __attribute__((visibility("hidden")))
#define CoTaskMemAlloc(p) malloc(p)
#define CoTaskMemFree(p) free(p)
//ANDROID
#elif (__ANDROID__ || ANDROID)
#define ANDROID_PLATFORM 1
#define DLLCALL
#define DLLIMPORT
#define DLLEXPORT __attribute__((visibility("default")))
#define DLLPRIVATE __attribute__((visibility("hidden")))
//MACOS
#elif defined(__APPLE__)
#include <unistd.h>
#include <termios.h>
#define DLLCALL
#define DLLIMPORT
#define DLLEXPORT __attribute__((visibility("default")))
#define DLLPRIVATE __attribute__((visibility("hidden")))
#include "TargetConditionals.h"
#if TARGET_OS_IPHONE && TARGET_IPHONE_SIMULATOR
#define IOS_SIMULATOR_PLATFORM 1
#elif TARGET_OS_IPHONE
#define IOS_PLATFORM 1
#elif TARGET_OS_MAC
#define MACOS_PLATFORM 1
#else
#endif
#endif
typedef std::string String;
typedef std::wstring WString;
#define EMPTY_STRING u8""s
#define EMPTY_WSTRING L""s
using namespace std::literals::string_literals;
class Strings
{
public:
static String WideStringToString(const WString& wstr)
{
if (wstr.empty())
{
return String();
}
size_t pos;
size_t begin = 0;
String ret;
#if WINDOWS_PLATFORM
int size;
pos = wstr.find(static_cast<wchar_t>(0), begin);
while (pos != WString::npos && begin < wstr.length())
{
WString segment = WString(&wstr[begin], pos - begin);
size = WideCharToMultiByte(CP_UTF8, WC_ERR_INVALID_CHARS, &segment[0], segment.size(), NULL, 0, NULL, NULL);
String converted = String(size, 0);
WideCharToMultiByte(CP_UTF8, WC_ERR_INVALID_CHARS, &segment[0], segment.size(), &converted[0], converted.size(), NULL, NULL);
ret.append(converted);
ret.append({ 0 });
begin = pos + 1;
pos = wstr.find(static_cast<wchar_t>(0), begin);
}
if (begin <= wstr.length())
{
WString segment = WString(&wstr[begin], wstr.length() - begin);
size = WideCharToMultiByte(CP_UTF8, WC_ERR_INVALID_CHARS, &segment[0], segment.size(), NULL, 0, NULL, NULL);
String converted = String(size, 0);
WideCharToMultiByte(CP_UTF8, WC_ERR_INVALID_CHARS, &segment[0], segment.size(), &converted[0], converted.size(), NULL, NULL);
ret.append(converted);
}
#elif LINUX_PLATFORM || MACOS_PLATFORM || EMSCRIPTEN_PLATFORM
size_t size;
pos = wstr.find(static_cast<wchar_t>(0), begin);
while (pos != WString::npos && begin < wstr.length())
{
WString segment = WString(&wstr[begin], pos - begin);
size = wcstombs(nullptr, segment.c_str(), 0);
String converted = String(size, 0);
wcstombs(&converted[0], segment.c_str(), converted.size());
ret.append(converted);
ret.append({ 0 });
begin = pos + 1;
pos = wstr.find(static_cast<wchar_t>(0), begin);
}
if (begin <= wstr.length())
{
WString segment = WString(&wstr[begin], wstr.length() - begin);
size = wcstombs(nullptr, segment.c_str(), 0);
String converted = String(size, 0);
wcstombs(&converted[0], segment.c_str(), converted.size());
ret.append(converted);
}
#else
static_assert(false, "Unknown Platform");
#endif
return ret;
}
static WString StringToWideString(const String& str)
{
if (str.empty())
{
return WString();
}
size_t pos;
size_t begin = 0;
WString ret;
#ifdef WINDOWS_PLATFORM
int size = 0;
pos = str.find(static_cast<char>(0), begin);
while (pos != std::string::npos) {
std::string segment = std::string(&str[begin], pos - begin);
std::wstring converted = std::wstring(segment.size() + 1, 0);
size = MultiByteToWideChar(CP_UTF8, MB_ERR_INVALID_CHARS, &segment[0], segment.size(), &converted[0], converted.length());
converted.resize(size);
ret.append(converted);
ret.append({ 0 });
begin = pos + 1;
pos = str.find(static_cast<char>(0), begin);
}
if (begin < str.length()) {
std::string segment = std::string(&str[begin], str.length() - begin);
std::wstring converted = std::wstring(segment.size() + 1, 0);
size = MultiByteToWideChar(CP_UTF8, MB_ERR_INVALID_CHARS, segment.c_str(), segment.size(), &converted[0], converted.length());
converted.resize(size);
ret.append(converted);
}
#elif LINUX_PLATFORM || MACOS_PLATFORM || EMSCRIPTEN_PLATFORM
size_t size;
pos = str.find(static_cast<char>(0), begin);
while (pos != String::npos)
{
String segment = String(&str[begin], pos - begin);
WString converted = WString(segment.size(), 0);
size = mbstowcs(&converted[0], &segment[0], converted.size());
converted.resize(size);
ret.append(converted);
ret.append({ 0 });
begin = pos + 1;
pos = str.find(static_cast<char>(0), begin);
}
if (begin < str.length())
{
String segment = String(&str[begin], str.length() - begin);
WString converted = WString(segment.size(), 0);
size = mbstowcs(&converted[0], &segment[0], converted.size());
converted.resize(size);
ret.append(converted);
}
#else
static_assert(false, "Unknown Platform");
#endif
return ret;
}
static WString ToUpper(const WString& data)
{
WString result = data;
auto& f = std::use_facet<std::ctype<wchar_t>>(std::locale());
f.toupper(&result[0], &result[0] + result.size());
return result;
}
static String ToUpper(const String& data)
{
return WideStringToString(ToUpper(StringToWideString(data)));
}
static WString ToLower(const WString& data)
{
WString result = data;
auto& f = std::use_facet<std::ctype<wchar_t>>(std::locale());
f.tolower(&result[0], &result[0] + result.size());
return result;
}
static String ToLower(const String& data)
{
return WideStringToString(ToLower(StringToWideString(data)));
}
};
enum class ConsoleTextStyle
{
DEFAULT = 0,
BOLD = 1,
FAINT = 2,
ITALIC = 3,
UNDERLINE = 4,
SLOW_BLINK = 5,
RAPID_BLINK = 6,
REVERSE = 7,
};
enum class ConsoleForeground
{
DEFAULT = 39,
BLACK = 30,
DARK_RED = 31,
DARK_GREEN = 32,
DARK_YELLOW = 33,
DARK_BLUE = 34,
DARK_MAGENTA = 35,
DARK_CYAN = 36,
GRAY = 37,
DARK_GRAY = 90,
RED = 91,
GREEN = 92,
YELLOW = 93,
BLUE = 94,
MAGENTA = 95,
CYAN = 96,
WHITE = 97
};
enum class ConsoleBackground
{
DEFAULT = 49,
BLACK = 40,
DARK_RED = 41,
DARK_GREEN = 42,
DARK_YELLOW = 43,
DARK_BLUE = 44,
DARK_MAGENTA = 45,
DARK_CYAN = 46,
GRAY = 47,
DARK_GRAY = 100,
RED = 101,
GREEN = 102,
YELLOW = 103,
BLUE = 104,
MAGENTA = 105,
CYAN = 106,
WHITE = 107
};
class Console
{
private:
static void EnableVirtualTermimalProcessing()
{
#if defined WINDOWS_PLATFORM
HANDLE hOut = GetStdHandle(STD_OUTPUT_HANDLE);
DWORD dwMode = 0;
GetConsoleMode(hOut, &dwMode);
if (!(dwMode & ENABLE_VIRTUAL_TERMINAL_PROCESSING))
{
dwMode |= ENABLE_VIRTUAL_TERMINAL_PROCESSING;
SetConsoleMode(hOut, dwMode);
}
#endif
}
static void ResetTerminalFormat()
{
std::cout << u8"\033[0m";
}
static void SetVirtualTerminalFormat(ConsoleForeground foreground, ConsoleBackground background, std::set<ConsoleTextStyle> styles)
{
String format = u8"\033[";
format.append(std::to_string(static_cast<int>(foreground)));
format.append(u8";");
format.append(std::to_string(static_cast<int>(background)));
if (styles.size() > 0)
{
for (auto it = styles.begin(); it != styles.end(); ++it)
{
format.append(u8";");
format.append(std::to_string(static_cast<int>(*it)));
}
}
format.append(u8"m");
std::cout << format;
}
public:
static void Clear()
{
#ifdef WINDOWS_PLATFORM
std::system(u8"cls");
#elif LINUX_PLATFORM || defined MACOS_PLATFORM
std::system(u8"clear");
#elif EMSCRIPTEN_PLATFORM
emscripten::val::global()["console"].call<void>(u8"clear");
#else
static_assert(false, "Unknown Platform");
#endif
}
static void Write(const String& s, ConsoleForeground foreground = ConsoleForeground::DEFAULT, ConsoleBackground background = ConsoleBackground::DEFAULT, std::set<ConsoleTextStyle> styles = {})
{
#ifndef EMSCRIPTEN_PLATFORM
EnableVirtualTermimalProcessing();
SetVirtualTerminalFormat(foreground, background, styles);
#endif
String str = s;
#ifdef WINDOWS_PLATFORM
WString unicode = Strings::StringToWideString(str);
WriteConsole(GetStdHandle(STD_OUTPUT_HANDLE), unicode.c_str(), static_cast<DWORD>(unicode.length()), nullptr, nullptr);
#elif defined LINUX_PLATFORM || defined MACOS_PLATFORM || EMSCRIPTEN_PLATFORM
std::cout << str;
#else
static_assert(false, "Unknown Platform");
#endif
#ifndef EMSCRIPTEN_PLATFORM
ResetTerminalFormat();
#endif
}
static void WriteLine(const String& s, ConsoleForeground foreground = ConsoleForeground::DEFAULT, ConsoleBackground background = ConsoleBackground::DEFAULT, std::set<ConsoleTextStyle> styles = {})
{
Write(s, foreground, background, styles);
std::cout << std::endl;
}
static void Write(const WString& s, ConsoleForeground foreground = ConsoleForeground::DEFAULT, ConsoleBackground background = ConsoleBackground::DEFAULT, std::set<ConsoleTextStyle> styles = {})
{
#ifndef EMSCRIPTEN_PLATFORM
EnableVirtualTermimalProcessing();
SetVirtualTerminalFormat(foreground, background, styles);
#endif
WString str = s;
#ifdef WINDOWS_PLATFORM
WriteConsole(GetStdHandle(STD_OUTPUT_HANDLE), str.c_str(), static_cast<DWORD>(str.length()), nullptr, nullptr);
#elif LINUX_PLATFORM || MACOS_PLATFORM || EMSCRIPTEN_PLATFORM
std::cout << Strings::WideStringToString(str);
#else
static_assert(false, "Unknown Platform");
#endif
#ifndef EMSCRIPTEN_PLATFORM
ResetTerminalFormat();
#endif
}
static void WriteLine(const WString& s, ConsoleForeground foreground = ConsoleForeground::DEFAULT, ConsoleBackground background = ConsoleBackground::DEFAULT, std::set<ConsoleTextStyle> styles = {})
{
Write(s, foreground, background, styles);
std::cout << std::endl;
}
static void WriteLine()
{
std::cout << std::endl;
}
static void Pause()
{
char c;
do
{
c = getchar();
std::cout << "Press Key " << std::endl;
} while (c != 64);
std::cout << "KeyPressed" << std::endl;
}
static int PauseAny(bool printWhenPressed = false, ConsoleForeground foreground = ConsoleForeground::DEFAULT, ConsoleBackground background = ConsoleBackground::DEFAULT, std::set<ConsoleTextStyle> styles = {})
{
int ch;
#ifdef WINDOWS_PLATFORM
ch = _getch();
#elif LINUX_PLATFORM || MACOS_PLATFORM || EMSCRIPTEN_PLATFORM
struct termios oldt, newt;
tcgetattr(STDIN_FILENO, &oldt);
newt = oldt;
newt.c_lflag &= ~(ICANON | ECHO);
tcsetattr(STDIN_FILENO, TCSANOW, &newt);
ch = getchar();
tcsetattr(STDIN_FILENO, TCSANOW, &oldt);
#else
static_assert(false, "Unknown Platform");
#endif
if (printWhenPressed)
{
Console::Write(String(1, ch), foreground, background, styles);
}
return ch;
}
};
int main()
{
std::locale::global(std::locale(u8"en_US.UTF-8"));
String dataStr = u8"Zoë Saldaña played in La maldición del padre Cardona. ëèñ αω óóChloë";
WString dataWStr = L"Zoë Saldaña played in La maldición del padre Cardona. ëèñ αω óóChloë";
std::string locale = u8"";
//std::string locale = u8"de_DE.UTF-8";
//std::string locale = u8"en_US.UTF-8";
Console::WriteLine(dataStr);
Console::WriteLine(dataWStr);
dataStr = Strings::ToUpper(dataStr);
dataWStr = Strings::ToUpper(dataWStr);
Console::WriteLine(dataStr);
Console::WriteLine(dataWStr);
dataStr = Strings::ToLower(dataStr);
dataWStr = Strings::ToLower(dataWStr);
Console::WriteLine(dataStr);
Console::WriteLine(dataWStr);
Console::WriteLine(u8"Press any key to exit"s, ConsoleForeground::DARK_GRAY);
Console::PauseAny();
return 0;
}
于 2020-10-18T06:22:51.753 回答