Re: How to convert a pointer to member function type to a const member one

On 1 Mag, 06:17, Greg Herlihy <gre...@[EMAIL PROTECTED]
> wrote:

>
> I'm assuming that you want to "synthesize" a member function pointer
> type for a const class method - given a member function pointer for an
> equivalent non-const class method.

Yes, this is similar to what I have to do, actually I have to do the
contrary: detect pointer to const member functions.


>
>      // General helper template declared - but not defined
>
>      template <class T>
>      struct AddConstToMemberFunctionPtr;
>
>      // specialized for member function pointers only
>
>      template <class R, class T, class P>
>      struct AddConstToMemberFunctionPtr<R (T::*)(P)>
>      {
>          typedef R (T::*type)(P) const;
>      };
>

This works but is not "general". It works only for pointer to member
with one argument.



I try to explain better the problem.


I have to detect if a functor type Fun has a given signature Sig, i.e.
if Fun::operator() has a signature Sig

What I have written til now is:


    /* Check if a function/functor Fun has a given signature Sig */
     template<typename Fun, typename Sig>
     struct is_compatible
     {
         /* Check for a function */
         template<class U> static
         yes_type check(typename enable_if<is_same<U, Sig> >::type*);

         /* Check for a functor */
         template<class U, Sig U::*> struct helper;

         template<class U> static
         yes_type check(helper<U, &U::operator()>*);

         /* Default */
         template<class U> static no_type check(...);

         typedef typename boost::remove_pointer<Fun>::type F;

         static bool const
         value = (sizeof(check<F>(0)) == sizeof(yes_type));
     };


Then
          is_compatible<Fun, Sig>::value

It's true iff Fun is a function or functor with signature Sig


It works nicely for any signature, i.e. for any argument number and
type, but it missed const members because


template<class U, Sig U::*> struct helper;

misses them. BTW writing

template<class U, Sig U::* const> struct helper;

does not im****ve anything.


I hope this is more clear on what I would need.

Thanks for your help
Marco


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