Re: [boost] Re: Re: multi_index_container

From: Joaquín Mª López Muñoz (joaquin_at_[hidden])
Date: 2005-03-02 02:38:27

Adding to my answer yesterday, seems like the compiler is just choking:
after reducing the complexity of the types involved, it works again OK.
The following tecnhique, which I call "type hiding" solves this issue and
also has other beneficial side effects in handicapped compilers.
Instead of defining your container like

typedef multi_index_container<
  employee,
  indexed_by<...>
> employee_set;

do it as follows

struct employee_set_indices:
  indexed_by<...>
{};

typedef multi_index_container<
  employee,
  employee_set_indices
> employee_set;

This generates much shorter symbol names and generally the compiler
has a happier time with it. In your particular case, I've confirmed that
it solves the problem with version D going crazy.

Docs in the next Boost release has a section on type hiding, as I think
it's a useful tecnhique when dealing with Boost.MultiIndex in not
so powerful environments.

Hope this helps,

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

Wusel ha escrito:

> Hi Joaquín M López Muñoz,
>
> thank you for your quick answer! I appreciate that multi_index_container
> exist and I can use it. In my opinion this library is very useful and
> facilitate many programs.
>
> >> 44   //version B: DOES compile
> >> 45   typedef index<employee_set,id >::type employee_set_by_id;
> >> 46   typedef index<employee_set,age>::type employee_set_by_age;
> >
> > OK, fine.
> >
> >> 48   //remove the name index (lines 31, 32) for following versions
> >> 49
> >> 50   //version C: DOES compile
> >> 51   typedef index<employee_set,id >::type employee_set_by_id;;
> >
> > OK, too.
> >
> >> 52
> >> 53   //version D: does NOT compile
> >> 54   //causes
> >> ...\include\boost-1_32\boost\mpl\vector\aux_\preprocessed\no_ctps\vector10.hpp(398)
> >> :
> >> 55   //  error C2039: 'item3' : is not a member of
> >> 'boost::mpl::vector2<T0,T1>'
> >> 56   typedef index<employee_set,age>::type employee_set_by_age;
> >
> > !! Here I'm missing somethig... Isn't version D exactly the same
> > as version B, which does work?
>
> Exact this I wanted point out. Version D differs from version B in
> removing two lines 31, 32 only (i.e. the name index). Version C is nearly
> the same, too. Nevertheless there is a difference when compiling.
>
> best regards
> Volker Vieth
>
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