Re: [boost] [fusion] map_gen interest

From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2008-04-06 10:44:40

AMDG

Sergei Politov wrote:
>   Sorry, I'm not very familiar with mpl::lambda, as far as I understand to 
> write make_vector<boost::mpl::_> I should support mpl::lambda in make_vector.
> If so it is not neccessary, as soon as it is just example, and it does not 
> belong to internal part of map_gen.
>   

No.  make_vector doesn't have to know about mpl::_.
map_gen has to use mpl::apply to make lambda expressions work.

>>> In other words it takes some fusion sequence and metafunction.
>>>       
>> MPL sequence?  There shouldn't be any runtime information associated 
>> with the key.
>>     
>   I meant: "fully conforming fusion sequences". As soon as it is possible to 
> adapt mpl sequence to fusion sequence, I suggest it is better to require fusion 
> sequence concept rather mpl sequence concept. Even runtime information is not 
> used. It produces no overhead, but makes map_gen more flexible.
>   

It's already pretty easy to make such a map using mpl sequences.

#include <boost/fusion/container/map.hpp>
#include <boost/fusion/include/convert.hpp>
#include <boost/fusion/support/pair.hpp>
#include <boost/fusion/adapted/mpl.hpp>
#include <boost/fusion/sequence/intrinsic/at_key.hpp>
#include <boost/mpl/vector.hpp>
#include <boost/mpl/transform.hpp>
#include <vector>

using namespace boost;
using namespace mpl::placeholders;

typedef fusion::result_of::as_map<
    mpl::transform<
        mpl::vector<int, char, double>,
        fusion::pair<_, std::vector<_> >
    >::type
 >::type map_type;

int main() {
    map_type map;
    fusion::at_key<int>(map).push_back(1);
    fusion::at_key<char>(map).push_back(1);
    fusion::at_key<char>(map).push_back(1.4);
    fusion::at_key<int>(map).push_back(1.4);
}

In Christ,
Steven Watanabe