C++ - What does the 'dot' operator means when used in std::cin.getline()?

Question

I'm used to program in Python, and since in Python, all are objects, it is totally acceptable when at the end of a variable, a . operator is used to access the method of a class. But in C++, let say for something like std::cin.getline(), is this some kind of accessing the member function of cin?

Is cin some kind of a class or a struct?

Did you try reading some documentation of `std::cin` to find out what it is? — Baum mit Augen, Jun 29 '16 at 21:08
I am also still kind of confuse with all of the syntax of C++ and how it actually works, so, I just think that by asking here, it would be better and more time saving. — Hafiz Hilman Mohammad Sofian, Jun 30 '16 at 09:22

score 6 · Accepted Answer · answered Jun 29 '16 at 21:40

Once you type:

#include <iostream>

the corresponding headerfile is inserted there. One line of this file reads

extern istream cin;

So as you see you have an object of type istream accessable from anywhere in the file with the include statement.

So your guess that cin is an instance of a class was right and the dot operator calls the getline method of that object/class.

Source: http://www.cplusplus.com/reference/iostream/cin/

score 4 · Answer 2 · answered Jun 29 '16 at 21:09

4

cin is indeed an instance of the class std::istream.

answered Jun 29 '16 at 21:09

Thomas B Preusser

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Edward Alexander · Answer 3 · 2016-06-29T21:39:52.183

2

std

Is the namespace

cin

Is an object from the istream class

getline

Is a method from the cin class.

edited Jun 29 '16 at 21:39

answered Jun 29 '16 at 21:32

Edward Alexander

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`cin` is not a class, it's a (global) variable. It is an instance of a class, though. – GManNickG Jun 29 '16 at 21:37
Oops, my bad. Thanks – Edward Alexander Jun 29 '16 at 21:37

C++ - What does the 'dot' operator means when used in std::cin.getline()?

3 Answers3