[boost] Re: boos::mpl::for_each: call function with return value

From: David Abrahams (dave_at_[hidden])
Date: 2003-11-01 14:53:42

Aleksey Gurtovoy <agurtovoy_at_[hidden]> writes:

> <digression>
> Of course ideally Fusion and MPL should interpolate 

Do you mean interoperate?

> so that the above could be written as
>
>     struct make_vehicle
>     {
>         template< typename T > struct result
>         {
>             typedef vehicle* type;
>         };
>
>         template< typename T >
>         vehicle* operator()(identity<T>, vehicle* ptr) const
>         {
>             return new T(ptr);
>         }
>     };
>
>     int main()
>     {
>         vehicle* result = fusion::fold(
>               fusion::identity_view< mpl::vector<vehicle,car,bicycle,train>
>>()
>             , static_cast<vehicle*>(0)
>             , make_vehicle
>             );
>
>         return 0;
>     }
> </digression>

I'm not sure why that's an improvement.  Is identity_view supposed to
default-construct a vehicle,car, bicycle, and train?

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com