Re: [Boost-users] Absolute Quanfusion : was Re: [fusion] transform avector of values to refs

From: Andy Little (andy_at_[hidden])
Date: 2006-09-08 16:39:21

"Andy Little" <andy_at_[hidden]> wrote
<...>

> Anyway I have continued hacking away and  so here is my latest efforts, using
> fusion to do a dot product of two vectors.
> Maybe it would be a useful example in the fusion docs?. Anyway here it is
> FWIW:

 A couple of bugs found in my code, as detailed below .  --->

Also I found I had to comment out the  specialisation of  as_vector<0>
in < boost/fusion/sequence/conversion/detail/as_vector.hpp>
in the Boost Review version to get it to compile OK in GCC4.0.1

I havent tried the CVS version of the file but it looks unchanged relative to my
version.

regards
Andy Little

<...>

> // more arg reversing
> template <typename F>
> struct reverse_f_args{
>
>    template <typename Rhs, typename Lhs>
>    struct result{
>        typedef typename F:: template result<
>            Rhs,Lhs
>        >::type type;
>    };
>    template <typename Rhs, typename Lhs>
>    typename result<Rhs,Lhs>::type
>    operator()( Rhs const & rhs, Lhs const & lhs )const
>    {
>        F f;
-----------------------
-        f(lhs,rhs);
+      return f(lhs,rhs);
----------------------
<...>

>    // do the dot_product
-----------------------------
-
-   result_type result = boost::fusion::fold(
-
+
+        result_type result = 0;
+
+        boost::fusion::fold(
-------------------------------------------------
>        boost::fusion::transform(seq1,seq2,quan::operator_times()),
>        boost::ref(result),
>        quan::fusion::reverse_assign_f_args<quan::operator_plus_equals>()
>    );
>    assert(quan::compare(result,30,1e-12) ==0);
>    std::cout << result <<'\n';
>
> }
> -----------------------------