[boost] Re: Interest in smart pointer with value semantics?

From: Dan W. (danw_at_[hidden])
Date: 2004-01-04 02:51:12

> The most important application of propagating constness is when storing an
> object by
> pointer in a class:
> 
> class X
> {
>     smart_ptr<My_polymorhic_type> p_;
> public:
>     int bar() const
>    {
>        return p_->this_is_also_a_const_function(); // compile time error if
> not
>     }
> };

That's neither a const, nor a non-const function of p_, you're calling; 
  it's a function of what p points to. That a function is const means 
that it doesn't change the class state, i.e.: what _address_ the pointer 
points to. But the target at that address is _not_ part of the state of 
this class, so why should the constness of a member function of _this_ 
class have to bear responsibility for some class elsewhere, just because 
we have its pointer?

If I said to you, I'll pay you a thousand dollars to keep this phone 
book for one night, and make sure it's not altered in any way, and you 
agree... Now, next day I come to pick up the phone book and you ask for 
the 1G, and I say, "well, you didn't do your job", and you say "how not? 
the book is safe!" and then I say "125 people died last night, that were 
listed in that phone book, you were to prevent that".