Re: [Boost-users] How to use the "type" member template pattern for using result_of?

Subject: Re: [Boost-users] How to use the "type" member template pattern for using result_of?
From: Eric Niebler (eric_at_[hidden])
Date: 2009-08-28 12:37:01

Jesse Perla wrote:
> 
> Take the following function:
> struct test_function
> {
>     template<typename Vector, typename IntType>
>     typename Vector::value_type
>     operator()(const Vector& x, IntType bound_value) const{
>         return x[0] * x[0] + bound_value;
>     }
> };
> 
> I wasn't sure exactly how the "type" member template pattern works so 
> that result_of will work.
> I tried the following, but can't figure out how to extract the type of 
> the arguments or convert to an MPL sequence?  Is there some trick I am 
> missing?
> 
> struct test_function
> {

       template<typename Sig>
       struct result;

       template<typename This, typename Vector, typename IntType>
       struct result<This(Vector, IntType)>
       {
           typedef
               typename boost::remove_reference<
                   Vector
               >::type::value_type
           type;
       };

>     template<typename Vector, typename IntType>
>     typename Vector::value_type //The type in the vector... can be a 
> double or AD type
>     operator()(const Vector& x, IntType bound_value) const{
>         return x[0] * x[0] + bound_value;
>     }
> };

HTH,

-- 
Eric Niebler
BoostPro Computing
http://www.boostpro.com