C++ std::string::npos常量（值为-1）（表示“直到字符串的结尾”，作为返回值，它通常用于表示不匹配）

• • cppman std::string::npos

std::string::npos(3)                                                  C++ Programmer's Manual                                                  std::string::npos(3)



NAME
       std::string::npos - Maximum value for size_t	//size_t 的最大值

TYPE
       public static member constant	//公共静态成员常量

SYNOPSIS
       #include 

       static const size_t npos = -1;

DESCRIPTION
       npos is a static member constant value with the greatest possible value for an element of type size_t.
       This value, when used as the value for a len (or sublen) parameter in string's member functions, means "until the end of the string".
       As a return value, it is usually used to indicate no matches.
       This  constant  is  defined  with  a value of -1, which because size_t is an unsigned integral type, it is the largest possible representable value for this
       type.
       //npos 是一个静态成员常量值，对于 size_t 类型的元素具有最大可能值。
        //此值在用作字符串成员函数中的 len（或 sublen）参数的值时，表示“直到字符串的结尾”。
        //作为返回值，它通常用于表示不匹配。
        //此常量定义为值 -1，因为 size_t 是无符号整数类型，所以它是该类型的最大可能表示值。

REFERENCE
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cplusplus.com                                                                2022-05-13                                                        std::string::npos(3)