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 wrote:

Eduardo Bezerra 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 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.

-- Dave Abrahams Boost Consulting www.boost-consulting.com

_______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

Actually after re-reading chapter 11 I got confused about the behavior of the mpl::fold algorithm. But the participants of this list kindly help me out. I don't have any more doubts now. Best Regards, Eduardo On 1/9/06, David Abrahams wrote:

Eduardo Bezerra writes:

...

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.

Sorry, I'm confused. did it help or did it leave you asking the boost-users list for an explanation?

...

Thanks for this wonderful work.

You're welcome.

-- Dave Abrahams Boost Consulting www.boost-consulting.com

_______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users