Re: [Boost-users] [multi_index] illegal indirection compile error

From: Themistoklis Bourdenas (themis_at_[hidden])
Date: 2006-08-01 06:52:09

Thanks for the reply. I will use the workaround for the time being until 
the new boost release comes up.

JOAQUIN LOPEZ MU?Z wrote:
> ----- Mensaje original -----
> De: Themistoklis Bourdenas <themis_at_[hidden]>
> Fecha: Lunes, Julio 31, 2006 4:47 pm
> Asunto: [Boost-users] [multi_index] illegal indirection compile error
> 
>> Could you help me understand what I'm doing wrong in the code 
>> below? I'm 
>> trying to setup a multi_index structure of class B.
>>
>> class A
>> {
>> 	const std::string& ID(void) const;
>> 	...
>> };
>>
>> class B : public A
>> {
>> 	...
>> };
>>
>> typedef boost::multi_index::multi_index_container<
>> 	B*,
>> 	boost::multi_index::indexed_by<
>>        	boost::multi_index::ordered_unique<
>>                	boost::multi_index::const_mem_fun<A, const 
>> std::string&, &A::ID>
>>        	>
>> 	>
>>> BSet;
>> However when I compile VS2005 returns me an "illegal indirection" 
>> compile error. Any thoughts?
> 
> Hello Themistoklis,
> 
> You've found a limitation in Boost.MultiIndex (as of Boost
> 1.33.1) by which one cannot specifiy a key in a given base
> class and pass derived classes as elements. This is solved
> in what will become Boost 1.34, please read bullet 3 of
> Boost.MultiIndex release notes at:
> 
> http://boost-
> consulting.com/boost/libs/multi_index/doc/release_notes.html#boost_1_34
> 
> Until this release is out, you can use the following
> workarond: simply define a custom key extractor like this
> (warning, I haven't compiled it, beware typos):
> 
> struct pB_ID_extractor
> {
>   typedef std::string result_type;
>   const std::string& operator()(const B* pb)const
>   {
>     return pb->ID();
>   }
> };
> 
> typedef boost::multi_index::multi_index_container<
>   B*,
>   boost::multi_index::indexed_by<
>     boost::multi_index::ordered_unique<
>       pB_ID_extractor
>     >
>   >
>> BSet;
> 
> Does this help? Thank you for using Boost.MultiIndex,
> 
> Joaquín M López Muñoz
> Telefónica, Investigación y Desarrollo