Re: [boost] Re: MPL - mpl::sequence to std::sequence

From: Terje Slettebø (tslettebo_at_[hidden])
Date: 2004-10-11 01:35:47

>From: "David Abrahams" <dave_at_[hidden]>

> Terje Slettebø <tslettebo_at_[hidden]> writes:
>
> >>From: "Terje Slettebø" <tslettebo_at_[hidden]>
> >>
> >> This way, we get:
> >>
> >>     copy<c_list>(std::back_inserter(r_list));
> >>
> >> Output of a compile-time sequence is also trivial:
> >>
> >>     copy<c_list>(std::ostream_iterator<int>(std::cout,","));
> >
> > Thinking about this some more, the only reason this works is that the
> > sequence consists of elements of the same type (integral_c derived), and
> > that it has an implicit conversion to the value type.
> >
> > However, it would also be possible to support heterogenous sequences,
but
> > then, the standard iterator adapters aren't sufficient, as they only
work
> > for homogenous sequences. That's possible to make, though.
> >
> > For fun, I knocked up this program, which stores values of a variety of
> > types in a compile-time sequence (char, int, double, rational_c and
> > std::string (wrapped)), prints the sequence out, copies it to a run-time
> > sequence (using boost::variant as element type), and prints it out,
> > again.
>
> You seem to be treading heavily into the territory of boost::fusion
> here, no?

That's hard to tell, given that there's hardly any docs on boost::fusion
(however, the library was on my mind when I mentioned "fusion of
compile-time and run-time" in an earlier posting, since that says in
fusion's docs. I didn't think this was anybody's territory in particular,
though (it seems very broad)). However, looking at the fusion docs, again,
it seems you're right. What I had originally thought about, was MPL (where
this thread originated). However, as you say, boost::fusion might be more
appropriate for it.

The above was only meant for inspiration and fun. If this functionality, or
something like it, already exists in boost::fusion, then great. However,
complaining about me treading into another library's territory, when I
haven't found any fence (docs, showing me that this exist already), seems a
bit unfair. (Maybe it wasn't meant as complaint, but it seemed that way. If
you had just mentioned that this exists in boost::fusion, or it may be more
appropriate for it, I wouldn't had a problem with it.)

Regards,

Terje