Boost Users :
From: Eduardo Bezerra (edubez_at_[hidden])
Date: 2006-01-09 08:01:46
Re-reading this great book for the 2nd time, and studying chapter
11 I found myself trying to understand the mpl::fold algorithm.
Thanks for this wonderful work.
My best regards,
On 1/8/06, David Abrahams <dave_at_[hidden]> wrote:
> Eduardo Bezerra <edubez_at_[hidden]> writes:
> > Hi,
> > I'm having a hard time trying to understand what the placeholders
> > _1 and _2 mean in the context of the mpl::fold algorithm.
> >>From the Boost.Mpl Reference manual:
> > typedef vector<long,float,short,double,float,long,long double> types;
> > typedef fold<
> > types
> > , int_<0>
> > , if_< is_float<_2>,next<_1>,_1 >
> >>::type number_of_floats;
> > BOOST_MPL_ASSERT_RELATION( number_of_floats::value, ==, 4 );
> > Could someone give me some help on this ?
> <shameless plug>
> http://www.boost-consulting.com/mplbook contains a good explanation.
> </shameless plug>
> Dave Abrahams
> Boost Consulting
> Boost-users mailing list
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