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

From: Ben Hutchings (ben.hutchings_at_[hidden])
Date: 2005-02-15 11:58:27

Jonathan Turkanis wrote:
> Sharon Galtzur wrote:
> 
> 
>>Thanks for the reply. The thing i dont understand is this :
>>template <class T> void f(int (T::*)(int)) will match any member
>>function with specific signature (receiving int and returning int).
>>But not all classes have such function. So in this case how will a
>>class F { } be matched ?
> 
> 
> No member of the given type need exist for the pointer-to-member type to be
> well-formed. Consider:
> 
>    struct C { };
> 
>    typedef void (C::*mem_fun) (std::string);
> 
> The later expression defines a type which can have no instances,
<snip>

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.

Ben.