[boost] If boost::fusion is the hammer, then what's the nail?

From: Weapon Liu (weapon.liu_at_[hidden])
Date: 2006-12-14 07:36:37

I think this is the right place to ask this question.
As cool as boost::fusion is, there's still one question that bothers me, 
that is, if boost::fusion is the hammer, then what's the nail?

I sure know that it's generic( more so than boost::tuple) and it's 
complete( with a bundle of algorithms and cool utilities), and it seems 
that it "solves" some problem quite well( when I read the documents).

However, I found it bothering that the documents didn't even mention one 
real-world application( boost libs aside).

Based on my experience, the most frequent scenarios where 
boost::tuple/fusion is useful are those where one needs a 
generated-on-the-fly struct for holding return values bundle, or where 
one needs to return multiple values transparently( well, nearly so), 
just like those lua does.

Other than that, I can't really imagine a scenario where this kinda 
stuff kicks butts. The biggest disadvantage of boost::fusion, I think, 
is that the size of it is known and fixed at compile time, which renders 
it not so qualified as a truly heterogeneous container.

And by the bye, that it can be used to build a handy pseudo-struct  that 
enables full introspection really is a good and fancy feature. However, 
there's something fundamentally irremediable of it, that is, it can't be 
used to build a full-fledged class( rather than a POD-struct), which, I 
think, will too reduce its usefulness w.r.t. this kinda situations.

I personally very like this fancy facility, and that's why I present 
these mumbles here to annoy you guys( if so, my apologies go here:-))
Any comments?