为什么 getline 的字符串版本是非成员函数？
The getline function has a character version that is a member function, as well as a global version that takes strings. Why aren't they both member functions? The current way makes it seems as though there isn't a string version.
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istream& istream::getline(char* s, Streamsize n)是流接口的一部分。istream& getline(istream& is, string& str)是string库中的扩展方法（就像istream &operator>> 一样） (istream&, string&))。选择这种设计可能是为了将 iostreams 与 string 解耦，因为 fstream::open() 也不采用 std： :string 参数，而是
const char*。istream& istream::getline(char* s, streamsize n)is part of the stream interface.istream& getline(istream& is, string& str)is an extension method from thestringlibrary (just like theistream &operator>>(istream&, string&)).This design was probably chosen in order to decouple iostreams from string, as
fstream::open()also does not takestd::stringarguments but ratherconst char*.因为 iostream 类的实现不应该依赖于字符串。
Because the implementation of the iostream classes should not depend on strings.
流库的问题在于它设计得不好。特别是成员函数
getline根本不应该存在。自由函数getline是正确的选择，它有几个优点：它不是成员函数，它是安全的，不在原始缓冲区上工作，并且不需要猜测。需要指出的是，成员函数和自由函数都是 istream 公共接口的一部分。
The trouble with stream library is that it's not well designed. In particular the member function
getlineshouldn't be there at all. The free functiongetlineis he right one to use, it has several advantages: it's not a member function, it's safe, not working on raw buffers, and requires no guesswork.It needs to be mentioned that both member- and free functions are part of istream public interface.