Re: [boost] [smart_ptr] shared_ptr template type

Subject: Re: [boost] [smart_ptr] shared_ptr template type
From: Stewart, Robert (Robert.Stewart_at_[hidden])
Date: 2009-07-15 08:44:22

Gottlob Frege wrote:
>
> My standard answer has now become:
>    1. use a traits/policy class
>    2. have the default traits/policy call a free functinon
>
> eg:
>
> // default free function
> // or yours will found by ADL if you supply your own
> //
> template<class T>  bool is_null_pointer(T p)
> {
>    return (p == 0);
> };
>
> // default policy class, calls whatever it finds by ADL
> // feel free to supply your own policy class instead
> //
> template<class T> struct default_smart_pointer_traits
>    : public smart_pointer_traits<T>
> {
>    static bool is_null(pointer p)
>    {
>         return is_null_pointer(p);
>    }
> };

That's a very nice approach.  You seem to lump traits and policy classes together, but they are clearly not equivalent.  I think a policy class is superior to a traits class, so your numbered bullets should not contain "traits/".

What about function templates?  The above seems to apply to class templates only.  Overloading permits one function template to rely on a default functor type while another can take a functor as an argument.  (The former can call the latter, of course.)  The functor argument can be defaulted, provided the default functor is stateless.

_____
Rob Stewart                           robert.stewart_at_[hidden]
Software Engineer, Core Software      using std::disclaimer;
Susquehanna International Group, LLP  http://www.sig.com

_____
Rob Stewart                           robert.stewart_at_[hidden]
Software Engineer, Core Software      using std::disclaimer;
Susquehanna International Group, LLP  http://www.sig.com

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