String operators 操作符 [C++ Reference]

String operators 操作符

Syntax:

语法：

    #include <string>
    bool operator==(const string& c1, const string& c2);
    bool operator!=(const string& c1, const string& c2);
    bool operator<(const string& c1, const string& c2);
    bool operator>(const string& c1, const string& c2);
    bool operator<=(const string& c1, const string& c2);
    bool operator>=(const string& c1, const string& c2);
    string operator+(const string& s1, const string& s2 );
    string operator+(const charT* s, const string& s2 );
    string operator+( charT c, const string& s2 );
    string operator+( const string& s1, const charT* s );
    string operator+( const string& s1, charT c );
    string& operator+=(const string& append);
    string& operator+=(const charT* append);
    string& operator+=(const charT  append);
    ostream& operator<<( ostream& os, const string& s );
    istream& operator>>( istream& is, string& s );
    string& operator=( const string& s );
    string& operator=( const charT* s );
    string& operator=( charT ch );
    charT& operator[]( size_type index );
    const charT& operator[]( size_type index ) const;

C++ strings can be compared and assigned with the standard comparison operators: ==, !=, <=, >=, <, >, and =. Performing a comparison or assigning one string to another takes linear time.

C++ strings 可以通过标准运算符 ==, !=, <=, >=, <, >, 和 = 进行比较和赋值。一个string和另一个string的比较或赋值操作是线性的。

Two strings are equal if:

两个strings是相等的，当：

Their size is the same, and
Each member in location i in one string is equal to the the member in location i in the other string.

它们的长度一样，而且
位于其中一个string的i处的元素与另一个string的i处的元素相等。

Comparisons among strings are done lexicographically.

strings 之间的比较是字典序的。

In addition to the normal container operators, strings can also be concatenated with the + operator and fed to the C++ I/O stream classes with the << and >> operators.

除了普通容器支持的运算符，strings 也可以通过 + 运算符进行连接，同时它也通过<< 和 >> 支持C++的输入/输出流。

For example, the following code concatenates two strings and displays the result:

例如，如下所示代码连接两个strings并显示其结果：

   string s1 = "Now is the time...";
   string s2 = "for all good men...";
   string s3 = s1 + s2;
   cout << "s3 is " << s3 << endl;

Furthermore, strings can be assigned values that are other strings, character arrays, or even single characters. The following code is perfectly valid:

更进一步，strings 可以通过其它strings，字符数组，甚至是单个字符进行赋值。例如，以下代码是合法的：

   char ch = 'N';
   string s;
   s = ch;

Individual characters of a string can be examined with the [] operator, which runs in constant time.

可以通过 [] 运算符检索string的单个字符，其复杂度是固定的