#### Archived

This topic is now archived and is closed to further replies.

This topic is 5847 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

## Recommended Posts

I''m trying to declare a friend function inside of a class and define it outside the class. My code basically looks like this: class Transition { . . friend bool operator<(Transition lhs, Transition rhs); . . }; bool operator<(Transition lhs, Transition rhs) { . . } MSVC++ gives me an error saying that (<) doesn''t have access to Transition''s private data. I don''t get the error if I define the function inside of the class "in-line" style. I would rather define it outside of the class if possible, cause it''s several lines of code. Every C++ book I have tells me that I can define it outside. Is this a bug in MSVC++? chris

##### Share on other sites
Why not do:

class classname
{
...
bool operator<(classname rhs);
...
};

bool classname::operator<(classname rhs)
{
...
}

the "lhs" is implied in the "this" pointer

{if(this->data < rhs.data) return true; return false; }

Edited by - Assassin on February 17, 2002 4:48:16 PM

##### Share on other sites
thanks for the help Assassin, anyway, apparently it is a bug, I just didn''t have the patch installed at the time. After I installed the service pack it compiled.

I''m trying to use my class in the STL set container, which requires you to declare the "less-than" operator. I''m not sure if I can use only the one argument version that you suggested.

chris

##### Share on other sites
quote:
Original post by Assassin
Why not do:

class classname
{
...
bool operator<(classname rhs);
...
};

bool classname::operator<(classname rhs)
{
...
}

Because this restricts the ability to use implicit conversions for the left-hand side of the expression. (Sometimes this is what you want, but very rarely.)

[ MSVC Fixes | STL | SDL | Game AI | Sockets | C++ Faq Lite | Boost ]

##### Share on other sites
Suppose the implicit this instance was declared constant - you now need to define/declare two flavors of operator<, one const, one non-const.

Unless Transition is a very small class, pass it by reference. And declare the actual function to be inline.
  friend bool operator<(const Transition& lhs, const Transition& rhs);