Re: [boost] Re: Policy or Trait?

From: Rob Stewart (stewart_at_[hidden])
Date: 2004-04-02 16:28:26

From: "Andy Little" <andy_at_[hidden]>
> 
> But is it the  flexibility that se wants.
                                  ^^
I try to use "s/he" for that.  "se" just looks like a typo.

>     #include <iostream>
>     template< typename A , typename B >
>     struct multiply_traits;
> 
> // use traits
>     template< typename A , typename B >
>     struct multiply1{
> 
>         typedef multiply_traits<A,B> traits;
>         typename traits::result_type operator ()
>             (typename traits::first_argument_type a,
>             typename traits::second_argument_type b)
>         {
>             return a * b;
>         }
> 
>     };

template< typename A, typename B >
class multiply1
{
   typedef multiply_traits<A,B> traits;
public:
   typedef typename traits::result_type result_type;
   typedef typename traits::first_argument_type first_argument_type;
   typedef typename traits::second_argument_type second_argument_type;

   result_type
   operator()(first_argument_type a, second_argument_type b)
   {
      return a * b;
   }
};

> //use policy
>     template< typename A , typename B, typename Policy>
>     struct multiply2{
> 
>         typename Policy::result_type operator ()
>             (typename Policy::first_argument_type a,
>             typename Policy::second_argument_type b)
>         {
>             return a * b;
>         }
> 
>      //   or Policy ()(a,b);  etc if ---> policy
> 
>     };

template< typename A, typename B, class Policy >
struct multiply2 : Policy
{
};

>     template<typename T>
>     struct multiply_traits<T,T>{
>         typedef T result_type;
>         typedef T first_argument_type;
>         typedef T second_argument_type;
>     //operator()(a,b) etc if --->policy
>     };
> 
> int main()
> {
>    multiply1<int,int>::traits::result_type val1

     multiply1<int,int>::result_type val1

>    = multiply1<int,int>()(10,10);
>    std::cout << val1 <<'\n';
> 
>    multiply_traits<int,int>::result_type val2
>    = multiply2<int,int,multiply_traits<int,int> >()(10,10);

     typedef multiply2< int, int, multiply_traits< int, int > > m2;
     m2::result_type val2(m2()(10, 10));

>    std::cout << val2 <<'\n';
> }

-- 
Rob Stewart                           stewart_at_[hidden]
Software Engineer                     http://www.sig.com
Susquehanna International Group, LLP  using std::disclaimer;