Re: [Boost-users] Re: starting to learn Boost MPL and type_trait

From: Ben Hutchings (ben.hutchings_at_[hidden])
Date: 2005-02-15 17:11:20

David Abrahams wrote:
> Ben Hutchings <ben.hutchings_at_[hidden]> writes:
> 
> 
>>Actually it can:
>>
>>    struct D : C { void foo(std::string); };
>>
>>    mem_fun mf = static_cast<mem_fun>(&D::foo);
>>
>>Not that I'd recommend doing that, as it invites type errors.
> 
> Creating an instance by breaking the type system is cheating.

That doesn't break the type system.  The result is well-defined; see 
5.2.9/9 in the standard.

> Why not reinterpret_cast<mem_fun>("foo"), for that matter?

That's ill-formed.

> A simpler instance of the type is:
> 
>   mem_fun mf = 0;

Yes, and as you know that's what the type trait relies on.

Ben.