Re: [Boost-users] [type_traits] superfluous add_pointer in function_traits or something else?

From: Tobias Schwinger (tschwinger_at_[hidden])
Date: 2007-01-25 13:36:39

Pavel Antokolsky aka Zigmar wrote:
>> 'T' is deduced to a function /pointer/. You have to use the plain
>> function type (without the pointer on top) for 'function_traits' to work:
>>
>>      typedef typename boost::function_traits<
>>          typename boost::remove_pointer<T>::type >::result_type X;
> Ah, thanks. That what I've been missing. I can of course
> "remove_pointer", but what I'm wandering, is why the function_traits
> tries to add pointer in a first place? 

It's done to please broken compilers, I guess.

Further, usually you want to accept both function objects and function 
pointers:

     template<typename R, typename F> void foo_impl(F f);

     template<class F>
     inline void foo(F f)
     {
         typedef typename F::result_type result;
         foo_impl<result>(f);
     }

     template<typename F>
     inline void foo(F * f)
     {
         typedef typename boost::function_traits<F>::result_type result;
         foo_impl<result>(f);
     }

And if done like this, the function type is deduced without a pointer.

Regards,
Tobias