Proto for Boost mailing list page: Re: [proto] My own lambda for MSM / wish list

Subject: Re: [proto] My own lambda for MSM / wish list
From: Christophe Henry (christophe.j.henry_at_[hidden])
Date: 2011-03-16 16:30:24

>Well, because it wasn't possible at the time, I assume ;)
>Times have changed since then ...

Indeed. Looks like it. :)

>> What I wanted to know:
>> - can I pass a phoenix expression to a decltype / BOOST_TYPEOF and
>> default-construct it?

>In general, no, because of various terminals that need to be initialized.
>You can however limit the phoenix grammar to only those expressions that can be default constructed.

If you mean all except, say, ints or chars, it's something I can live
with because I already do ;-)

>Why not copy construct them?

I don't see how it would help. I mean, the transition table I'm
generating with the grammar ist and mpl::vector< Row<...>, Row<...> >.
Then run my metaprograms and I have nothing left to construct from.

>Yes, the entry point is pretty high, but i hope its worth it ... If you come to the conclusion that writing your own library is faster and easier phoenix maybe isn't quite >ready for prime time with that respect.

No, it's not what I mean. The library is already written, since about
1 year, it's inside MSM's eUML front-end (see for example
http://www.boost.org/doc/libs/1_46_0/libs/msm/doc/HTML/ch03s04.html#d0e2059).

But the implementation will not win a beauty contest ;-)
So I'm rewriting it and the examples I presented in this thread are
only a cleaned-up, smaller version to show what I'm looking for, with
some stuff I added after I realized it was not usable only with MSM.
Now that I tried to explain what I was looking for and after your
answers and some time I just spent investigating phoenix, I think it's
worth giving a try with phoenix.

So if you accept helping me a bit to come to speed with phoenix
internals, I think MSM can pretty fast be your first "client" ;-)
If you don't mind, I offer to close this thread and start hacking
code. I already have the first questions ready.

>I am looking forward to improvments in the docs, or additions to code you might have!

Sure, we'll see on the way what I'm missing.

Thanks,
Christophe