Re: [boost] quince: queries in C++ expressions

Subject: Re: [boost] quince: queries in C++ expressions
From: Michael Shepanski (mps_at_[hidden])
Date: 2014-07-21 07:01:47

On 21/07/2014 6:53 PM, Mathias Gaunard wrote:
> On 15/07/14 14:45, Michael Shepanski wrote:
>
>> Could you clarify what you mean by "do this"?  QUINCE_MAP_CLASS builds a
>> class with exactly the data members, function members, and bases that
>> quince requires.
>
> Boost.Fusion defines tuple concepts, and provides utilities to adapt a 
> class to a tuple (or define a class and adapt it at the same time).
>
> To maximize compatibility, and to prevent users having to say that 
> their structure is tuple-like a billion times, it's better to reuse this.

So you are suggesting that users who want to say QUINCE_MAP_CLASS be 
made to say BOOST_FUSION_ADAPT_STRUCT instead?

I see that BOOST_FUSION_ADAPT_STRUCT asks users to repeat the members' 
types, in a way that QUINCE_MAP_CLASS doesn't. (Why is that, btw?)

I don't (yet) see how BOOST_FUSION_ADAPT_STRUCT could be used to replace 
QUINCE_MAP_CLASS_WITH_BASES.

Also I don't see how any of this is going to produce the mapper classes 
with all the specific features that the rest of quince needs. I think 
that would be an extra step.

> Any type that is Fusion-compatible should be made compatible with your 
> library too.

Quince already allows std::tuples to be mapped types. So I guess quince 
could, similarly, allow fusion sequences to be mapped types. Then a user 
who has a class could indeed choose to get it mapped by the circuitous 
route of adapting it to a Fusion sequence and then mapping that. (It 
wouldn't be my choice, but to each his own.)

> Also, building as you do seems quite intrusive. You probably want to 
> support a non-intrusive approach anyway.

What do you mean?
--- Michael