Thread: insertion operator question

I'm not sure what you're asking.
http://gethelp.devx.com/techtips/cpp.../10min0400.asp

>How does the << operator works??
This gets my vote for the "innocent question with a REALLY long and complicated answer" award.

Basically it calls a member function for the stream called operator<< to do the actual ouput. Thus:

Code:

double foo = 18.9;
cout << foo;

Is equivalent to:

Code:

double foo = 18.9;
cout.operator<<(foo);

This member function is overloaded to handle all the basic primary data types (ints, floats, chars, doubles, char *, etc...). Additional user defined types (classes,structs) can also be created and the operator<< function overloaded to support the writing of those particular object to the stream in question.

The function's return type is a reference to the modified stream which allows them to be chained together thus you can do:

Code:

double foo = 18.9;
char * bar = "Hello World";
cout << foo << ' ' << bar;

which is equivalent to three seperate calls:

Code:

double foo = 18.9;
char * bar = "Hello World";
cout.operator<<(foo);
cout.operator<<(' ');
cout.operator<<(bar);

Yeah... this can get a bit involved but that's a quick and dirty primer.