Re: [boost] Re: Re: Re: Re: relational table asanSTLcontainer--anyinterest?

From: Joel de Guzman (djowel_at_[hidden])
Date: 2002-11-01 21:14:07

----- Original Message ----- 
From: "Joel de Guzman" <djowel_at_[hidden]>
Subject: Re: [boost] Re: Re: Re: Re: relational table asanSTLcontainer--anyinterest?

> ----- Original Message ----- 
> From: "Arkadiy Vertleyb" <vertleyb_at_[hidden]>
> 
> > 
> > There were many times when I PROVED that something can't be done, and then
> > actualy did it...  Or somebody else did it.  :o))
> 
> Surely!
> 
> > > Another comment is the tuple. I think boost tuples can be used.
> > >
> > 
> > Boost  tuples allow the access by the position number.  To access by name,
> > we would have to somehow map the name to the position number.  We would
> > probably have to use strings to define names, which would elliminate the
> > posibility of compile time checks.  Also, static_cast should be
> > significantly faster than iterating through boost::tuple fields.
> 
> I do not agree with you. First, the "iteration" is optimized
> by the compiler. Second, which is also related to my previous
> comment on MACROs, I don't see any reason why fields and
> columns can't be refered to by place holders as do boost.bind,
> boost.lambda, boost.tuples and phoenix. Names? Sure you can
> use names. Here's an example using Phoenix:
> 
>     tuple_index<0> my_field;
>     val = tup[my_field];
> 
> see http://spirit.sourceforge.net/index.php?doc=docs/phoenix_v1_0/tuples.html 

BTW, if you wish to have the tup.field syntax, you might find
inspiration in boost.spirit closures. Example syntax:
 
    struct my_tuple : tuple_fields<my_tuple, std::string, int, int>
    {
        member1 name;
        member2 id;
        member3 age;
    };

Then:

    my_tuple tup;
    std::cout << tup.name << std::endl;

see http://spirit.sourceforge.net/index.php?doc=docs/v1_5/closures.html

Regards again,
--Joel