Re: [boost] MPL's "round" lambda

From: Peter Dimov (pdimov_at_[hidden])
Date: 2002-11-18 09:17:29

From: "Joel de Guzman" <djowel_at_[hidden]>
> From: "Peter Dimov" <pdimov_at_[hidden]>
> > From: "Aleksey Gurtovoy" <agurtovoy_at_[hidden]>
> > > If you are tired of angle brackets in your templates (no, it's not a
TV
> > > commercial :), may be you'll like this one:
> > >
> > >     typedef eval<
> > >           count_if(
> > >               list(int,char,long,int)
> > >             , lambda(is_same(_,int))
> > >             )
> > >         >::type res;
> > >
> > >     BOOST_STATIC_ASSERT(res::value == 2);
> >
> > OK, I give up. How does this work?
>
> I've been twisting my mind very hard the past hour trying to
> imagine how this will work without peeking at the code.
> Whew, this is a tough one to crack!

I wrote "I don't understand how it works even _after_ (briefly) looking at
the code. ;-)" but then it occured to me that list(int, char, long, int) is
a function type. Cool trick. Cv qualifiers will probably be a problem but
it's cool. Aleksey wins the Boost obfuscated C++ contest of the week.