Question

Is their a way to use a non-member non-friend function on an object using the same ‘dot’ notation as member functions?

Can I pull a (any) member out of a class, and have users use it in the same way they always have?

Longer Explanation:

Scott Meyers, Herb Sutter, et all, argue that non-member non-friend functions are a part of an object’s interface, and can improve encapsulation. I agree with them.

However, after recently reading this article: http://www.gotw.ca/gotw/084.htm I find myself questioning the syntax implications.

In that article, Herb proposes having a single insert, erase, and replace member, and several non-member non-friend functions of the same name.

Does this mean, as I think it does, that Herb thinks some functions should be used with the dot notation, and others as a global function?

std::string s('foobar');  s.insert( ... ); /* One like this */ insert( s , ...); /* Others like this */ 

Edit:

Thanks everyone for your very useful answers, however, I think the point of my question has been overlooked.

I specifically did not mention the specific case of operators, and how they retain the ‘natural’ notation. Nor that you should wrap everything in a namespace. These things are written in the article I linked to.

The question itself was:

In the article, Herb suggests that one insert() method be a member, while the rest are non-member non-friend functions.

This implies that to use one form of insert() you have to use dot notation, while for the others, you do not.

Is it just me, or does that sound crazy?

I have a hunch that perhaps you can use a single syntax. (Im thinking how Boost::function can take a *this parameter for mem_fun).

Answer 1

You can use a single syntax, but perhaps not the one you like. Instead of placing one insert() inside your class scope, you make it a friend of your class. Now you can write

mystring s; insert(s, 'hello'); insert(s, other_s.begin(), other_s.end()); insert(s, 10, '.'); 

For any non-virtual, public method, it’s equivalent to define it as a non-member friend function. If mixed dot/no-dot syntax bothers you then by all means make those methods friend functions instead. There’s no difference.

In the future we will also be able to write polymorphic functions like this, so maybe this is the C++ way, rather than artificially trying to force free functions into the dot syntax.