Re: [Boost-users] problem in returning mpl::list

From: John C. Femiani (john.femiani_at_[hidden])
Date: 2008-07-27 23:36:28

Stjepan Rajko wrote:
> 2008/7/27 noman javed <noman_bwp_at_[hidden]>:
>   
>> struct Poplist
>> {
>>     template<class seq>
>>     struct apply
>>     {
>>         typedef pop_front<seq>::type res;
>>         static const int value = size<seq>::value;
>>     };
>> };
>>     
>
> for starts, you need to use typename here:
>
> typedef typename pop_front<seq>::type res;
>   
Also, apply does not have a 'type' member typedef, so I think it is not 
a metafunction.

What about (untested)

     namespace mpl = ::boost::mpl;
    struct Poplist : mpl::lambda<mpl::pop_front<mpl::placeholders::_1>
     >::type {}

or (untested)

    struct poplist{
        template<class Seq> struct apply :  mpl::pop_front<Seq> {};
    };

I think section 3.2 of Abraham's 'C++ Template Metaprogramming' book has 
some examples.

--John