Re: [boost] [fusion] [intro] ADAPT_STRUCT extensions

Subject: Re: [boost] [fusion] [intro] ADAPT_STRUCT extensions
From: Stefan Strasser (strasser_at_[hidden])
Date: 2010-07-29 18:35:18

Zitat von Hartmut Kaiser <hartmut.kaiser_at_[hidden]>:

>> 1)
>>
>> ADAPT_STRUCT can adapt public data members only.
>>
>> with the modifications I uploaded here:
>> http://svn.boost.org/svn/boost/sandbox/intro/boost/fusion/adapted/struct/
>>
>> all data members can be adapted. for example:
>>
>> class A{
>> private:
>>    friend class fusion::access;
>>    int a;
>> };
>>
>> BOOST_FUSION_ADAPT_STRUCT(A,(int,a) )
>>
>> 2)
>>
>> adaption of a class including its base class members. for example:
>>
>> struct A{ int a; };
>> struct B{ int b; };
>> struct C : A,B{ int c; }
>>
>> BOOST_FUSION_ADAPT_STRUCT(A,(int,a) )
>> BOOST_FUSION_ADAPT_STRUCT(B,(int,b) )
>> BOOST_FUSION_ADAPT_DERIVED(
>>    C, (A)(B),
>>    (int,c)
>> )
>>
>> an instance of C is now a fusion sequence of size 3.
>> http://svn.boost.org/svn/boost/sandbox/intro/boost/fusion/adapted/struct/a
>> dapt_derived.hpp
>>
>> private inheritance is supported as above, virtual inheritance is not.
>> I'm not sure if virtual inheritance can be supported.
>
> Have you seen the new BOOST_FUSION_ADAPT_CLASS() family of utilities which
> allow using (member-) functions instead of direct access to the data members
> of a class/struct?

no I had not, I was using 1.41. where can I see those? can't seem to  
find them in 1.43 or the trunk.

do these solve one of the two issues above?
in case you brought it up because then you could have public accessor  
functions to private members, I'd still propose to add a way to adapt  
private members as shown above.
I'd like to use this for what is apparently known as the "scrap your  
boilerplate" pattern in the functional programming world (see the  
previous [intro] discussion), which requires adapting each member in  
every class used in such an algorithm. there obviously shouldn't be  
public accessors for all members.

best,
Stefan