question regarding some c++ syntax

[xephon]

I'm reading The C++ Standard Library. within the implementation for auto_ptr, there is this line:

struct auto_ptr_ref {
     Y* yp;
     auto_ptr_ref (Y* rhs)
       : yp(rhs) {       <-- this is the line
     }
};

I'm wondering what ":yp(rhs)" and the following parentheses doing here? Anyone care to explain?

Thanks

[blackcoder41]

It is called initialization list.

Here have a read.
http://www.cprogramming.com/tutorial/initialization-lists-c++.html

[xephon]

thx man, that cleared things up.