Re: [Boost-users] [multiindex] [bind] Conversion loses qualifiers

From: Nebojsa Simic (nelle_at_[hidden])
Date: 2007-11-16 16:56:06

Nebojsa Simic wrote:
> Hello all,
> 
> First of all, thanks for a wonderful library, it is a pleasure to work
> with...
> 
> However I ran into some problems and I can not find the answers either
> on the Internet nor on this mailing list. The problem at hand concerns
> the multiindex container and bind.
> 
> I have a class with the following member:
> 
> class Statistics {
> public:
> 	void addStats ( double val, int tick );
> }
> 
> and a container:
> 
> typedef multi_index_container< Statistics,
>     indexed_by <ordered_unique<identity<Statistics> >,
>       ordered_non_unique< member<Statistics,double,&Statistics::gamma> >
>     >
>   > StatisticsMap;
> 
> StatisticsMap m_statistic;
> 
> indexed by :
> 
> typedef StatisticsMap::nth_index<1>::type StatisticsByResponse;
> 
> somewhere in code i try to do this :
> 
> std::pair<StatisticsMap::iterator,bool> result = m_statistic.insert(
> Statistics( response, value, tick ) );
> 
> StatisticsByResponse& idxResponse = m_statistic.get<1>();
> StatisticsByResponse::iterator it = m_statistic.project<1>(result.first );
> 
> the problem comes when I try to update the statistics by using :
> 
> for_each( it
>     , idxResponse.end()
>     , boost::bind( &Statistics::addStats, ::_1, val, tick )
>   );
> 

Ok, the elements in the container are constant and may not be changed
through iterators. For multiindex container the modify method must be
used to change them.

So I changed the last line to :

boost::function<void(Statistics&)> fnAddStats  = boost::bind(
&Statistics::addStats, ::_1, val, tick );

for_each( it
    , idxResponse.end()
    , boost::bind( &StatisticsByResponse::modify,
boost::ref(idxResponse), ::_1, fnAddStats )
  );

but it still does not compile (problem with boost::bind "wrong number of
arguments").

the call :
idxResponse.modify( it, fnAddStats );
works, so the problem is not the first bind, but the one in for_each.

-- 
Nebojsa Simic