Hi Dave, 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, Eduardo On 1/8/06, David Abrahams <dave@boost-consulting.com> wrote:
Eduardo Bezerra <edubez@gmail.com> 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 www.boost-consulting.com
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