RE: [Boost-Users] MPL?

From: Jeff Faust (jeff_at_[hidden])
Date: 2002-10-02 14:36:52

Well, I didn't know I needed boost until I saw it.  Same for STL several
years back.  'Metaprogramming' comes up a lot on the boost list, but I have
no understanding about what it's for--what problems it solves.  The
documentation is sparse.  Then this thread comes up and everybody talks
about it like it's obvious.  I dislike being baffled.

But mostly it's curiosity.  I need something to talk about at parties and
impress the ladies.  MPL will do that, right?  Right?  Hello?

Jeff

-----Original Message-----
From: David B. Held [mailto:dheld_at_[hidden]]
Sent: Wednesday, October 02, 2002 12:14 PM
To: Boost-Users_at_[hidden]
Subject: Re: [Boost-Users] MPL?

----- Original Message -----
From: "Jeff Faust" <jeff_at_[hidden]>
To: <Boost-Users_at_[hidden]>
Sent: Wednesday, October 02, 2002 11:32 AM
Subject: [Boost-Users] MPL?

> [...]
> Can anybody explain in English what the following does?

I believe that Aleksey posted the runtime pseudo-equivalent.

> Posted by David Abrahams on boost developers list:
> > Have I mentioned recently how totally cool MPL's lambda facility is?
> > I can't believe I can do things like this, even with MSVC6. It makes my
> > metaprograms SO much easier to manage!
> >      mpl::logical_and<
> >         is_reference_to_class<add_reference<mpl::_> >
> >       , mpl::logical_not<
> >             is_reference_to_args<add_reference<mpl::_> >

[Aleksey, on 9/27]
// "ideal" version, for comparison purposes:
//  is_reference_to_class( add_reference(_) )
//  && !is_reference_to_args( add_reference(_) )

I can't say for sure what the code does myself, but if I could venture
a guess, I would say that it's a condition for something else (maybe
an iterative algorithm over a type container?) that checks to see if
an argument is a reference type of various sorts.

Basically, if you don't understand it, in this case, you probably don't
need it. ;)  I know I don't!

Dave

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