Re: boost::bind related question

From: rwgk (rwgk_at_[hidden])
Date: 2002-02-27 23:36:22

--- In boost_at_y..., "David Abrahams" <david.abrahams_at_r...> wrote:
> How would typeof() solve this problem? You can deduce the return 
type, but
> we need a way to treat the entire wad of overloads for any given 
name as a
> single runtime entity to be resolved only at the point of 
invocation.
> Another important extension I hadn't thought of...
> 
> -Dave

For the records, the solution to my problem works without boost::bind.
It involves a special functor for each function in <cmath>, e.g.:

>  template <typename ResultType,
>            typename ArgumentType>
>  struct functor_acos {
>    ResultType operator()(const ArgumentType& x) const {
>      return ResultType(acos(x));
>    }
>  };

Here is how the functor is used (look for the ************,
shared<> is a reference-counted substitute for std::vector<>):

>  template<typename ElementType>
>  inline
>  shared<
>    typename unary_operator_traits<
>        ElementType>::arithmetic>
>  acos(const shared<ElementType>& a) {
>    typedef shared<
>      typename unary_operator_traits<
>          ElementType>::arithmetic>
>    result_array_type;
>    typedef typename result_array_type::value_type 
return_element_type;
>    result_array_type result(a.size(), reserve_flag());
>    //                    ************
>    array_operation_unary(functor_acos<return_element_type, 
ElementType>(),
>    //                    ************
>      a.begin(), result.begin(), a.size(),
>      has_trivial_destructor<return_element_type>::value());
>    result.set_size_back_door(a.size());
>    return result;
>  }

Thanks for all the help!
        Ralf