Re: [Boost-users] [multiindex] [bind] Update members of the container between two iterators

----- Mensaje original ----- De: Nebojsa Simic Fecha: Sábado, Noviembre 17, 2007 4:02 pm Asunto: Re: [Boost-users] [multiindex] [bind] Update members of the container between two iterators Para: boost-users@lists.boost.org

JOAQUIN LOPEZ MU?Z wrote: [...]

...

You can't use for_each(it1,it2,someFunctor) to do what you want because> modify() needs an iterator, and for_each passes a value reference> to someFunctor rather than the iterator. So, you've got to resort to a handmade loop like:

So, the current status is:

// TEMPLATE FUNCTION for_each_it template inline _Fn1 for_each_it(_InIt _First, _InIt _Last, _Fn1 _Func) { // perform function for each element for (; _First != _Last; ++_First) _Func(_First); return (_Func); };

and when I try to do this :

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

still get compilation errors. What am I missing here ?

as a temporary solution I added :

inline bool bloodyBindable( StatisticsByResponse& index, const StatisticsByResponse::iterator& it, boost::function fnc ) { return index.modify( it, fnc ); }

for_each_it( it , idxResponse.end() , boost::bind( bloodyBindable, idxResponse, ::_1, fnAddW0 ) );

which compiles, but I just want to know what am I doing wrong.

Two things: 1. The expression boost::bind(bloodyBindable,idxResponse,::_1,fnAddStats) does a copy of the idxResponse index, which is not what you want (indices are actually not copyable, more info on why you can still get spurious index copies in certain compilers at http://lists.boost.org/boost-users/2007/10/31777.php ). So, to prevent this copying use boost::ref: boost::bind(bloodyBindable,boost::ref(idxResponse),::_1,fnAddStats) More info on the usage of Boost.Ref with Boost.Bind at http://boost.org/libs/bind/bind.html . 2. The reason why you can't do the binding directly and have to resort to the bloodyBindable proxy is that modify is *not* a member function, but a member function *template*. To do the binding you have to provide an instantiation of modify, like this: for_each_it( it,idxResponse.end(), boost::bind( &StatisticsByResponse::modify

, boost::ref(idxResponse),::_1,fnAddStats));

Joaquín M López Muñoz Telefónica, Investigación y Desarrollo