对大小写不敏感的比较没有成为标准string类的一部分
希伯来语 波斯语 和汉语 日本语并不使用大小写概念，对这些语言
来说大小写没意义
还有西班牙语中的变音符号，法语中的抑扬符号，德语中的元音变音，
任何试图全面解决问题的大小写敏感的分类整理方案，会变得复杂
可用信息构造一种忽略大小写的新类型string类
//: C03:ichar_traits.h
// From "Thinking in C++, Volume 2", by Bruce Eckel & Chuck Allison.
// (c) 1995-2004 MindView, Inc. All Rights Reserved.
// See source code use permissions stated in the file 'License.txt',
// distributed with the code package available at www.MindView.net.
// Creating your own character traits.
#ifndef ICHAR_TRAITS_H
#define ICHAR_TRAITS_H
#include <cassert>
#include <cctype>
#include <cmath>
#include <cstddef>
#include <ostream>
#include <string>
using std::allocator;
using std::basic_string;
using std::char_traits;
using std::ostream;
using std::size_t;
using std::string;
using std::toupper;
using std::tolower;
struct ichar_traits : char_traits<char> {
// We'll only change character-by-
// character comparison functions
static bool eq(char c1st, char c2nd) {
return toupper(c1st) == toupper(c2nd);
}
static bool ne(char c1st, char c2nd) {
return !eq(c1st, c2nd);
}
static bool lt(char c1st, char c2nd) {
return toupper(c1st) < toupper(c2nd);
}
static int
compare(const char* str1, const char* str2, size_t n) {
for(size_t i = 0; i < n; ++i) {
if(str1 == 0)
return -1;
else if(str2 == 0)
return 1;
else if(tolower(*str1) < tolower(*str2))
return -1;
else if(tolower(*str1) > tolower(*str2))
return 1;
assert(tolower(*str1) == tolower(*str2));
++str1; ++str2; // Compare the other chars
}
return 0;
}
static const char*
find(const char* s1, size_t n, char c) {
while(n-- > 0)
if(toupper(*s1) == toupper(c))
return s1;
else
++s1;
return 0;
}
};
typedef basic_string<char, ichar_traits> istring;
inline ostream& operator<<(ostream& os, const istring& s) {
return os << string(s.c_str(), s.length());
}
#endif // ICHAR_TRAITS_H ///:~该程序提供了一个typedef命名的istring类，这样该类就能在各方面
像普通的string类一样工作，除了在进行比较的时候不考虑大小写
//: C03:ICompare.cpp
// From "Thinking in C++, Volume 2", by Bruce Eckel & Chuck Allison.
// (c) 1995-2004 MindView, Inc. All Rights Reserved.
// See source code use permissions stated in the file 'License.txt',
// distributed with the code package available at www.MindView.net.
#include <cassert>
#include <iostream>
#include "ichar_traits.h"
using namespace std;
int main() {
// The same letters except for case:
istring first = "tHis";
istring second = "ThIS";
cout << first << endl;
cout << second << endl;
assert(first.compare(second) == 0);
assert(first.find('h') == 1);
assert(first.find('I') == 2);
assert(first.find('x') == string::npos);
getchar();
} ///:~
输出
tHis
ThIS
没出现异常对话框
它只是一个很小的也没有什么事业价值的例子
在宽字符流 wide stream和头文件 <cwctype>中，也体现出对宽字符串的
支持
//: C03:ichar_traits.h
// From "Thinking in C++, Volume 2", by Bruce Eckel & Chuck Allison.
// (c) 1995-2004 MindView, Inc. All Rights Reserved.
// See source code use permissions stated in the file 'License.txt',
// distributed with the code package available at www.MindView.net.
// Creating your own character traits.
#ifndef ICHAR_TRAITS_H
#define ICHAR_TRAITS_H
#include <cassert>
#include <cctype>
#include <cmath>
#include <cstddef>
#include <ostream>
#include <string>
using std::allocator;
using std::basic_string;
using std::char_traits;
using std::ostream;
using std::size_t;
using std::string;
using std::toupper;
using std::tolower;
struct ichar_traits : char_traits<char> {
// We'll only change character-by-
// character comparison functions
static bool eq(char c1st, char c2nd) {
return toupper(c1st) == toupper(c2nd);
}
static bool ne(char c1st, char c2nd) {
return !eq(c1st, c2nd);
}
static bool lt(char c1st, char c2nd) {
return toupper(c1st) < toupper(c2nd);
}
static int
compare(const char* str1, const char* str2, size_t n) {
for(size_t i = 0; i < n; ++i) {
if(str1 == 0)
return -1;
else if(str2 == 0)
return 1;
else if(tolower(*str1) < tolower(*str2))
return -1;
else if(tolower(*str1) > tolower(*str2))
return 1;
assert(tolower(*str1) == tolower(*str2));
++str1; ++str2; // Compare the other chars
}
return 0;
}
static const char*
find(const char* s1, size_t n, char c) {
while(n-- > 0)
if(toupper(*s1) == toupper(c))
return s1;
else
++s1;
return 0;
}
};
typedef basic_string<char, ichar_traits> istring;
inline ostream& operator<<(ostream& os, const istring& s) {
return os << string(s.c_str(), s.length());
}
#endif // ICHAR_TRAITS_H ///:~基本是一个要求在源代码中的适当位置放置一个‘w'
//: C03:IWCompare.cpp {-g++}
// From "Thinking in C++, Volume 2", by Bruce Eckel & Chuck Allison.
// (c) 1995-2004 MindView, Inc. All Rights Reserved.
// See source code use permissions stated in the file 'License.txt',
// distributed with the code package available at www.MindView.net.
#include <cassert>
#include <iostream>
#include "iwchar_traits.h"
using namespace std;
int main() {
// The same letters except for case:
iwstring wfirst = L"tHis";
iwstring wsecond = L"ThIS";
wcout << wfirst << endl;
wcout << wsecond << endl;
assert(wfirst.compare(wsecond) == 0);
assert(wfirst.find('h') == 1);
assert(wfirst.find('I') == 2);
assert(wfirst.find('x') == wstring::npos);
getchar();
} ///:~
输出
tHis
ThIS
有些编译器对宽字符没有提供足够的支持