Re: [boost] Proposed: a new sequence adapter for MPL (product_view)

From: Larry Evans (cppljevans_at_[hidden])
Date: 2008-03-14 14:19:50

On 03/12/08 20:21, Max Motovilov wrote:
> Some final comments.
> 
> First, in the code I posted above "push_back< S, A>" should be replaced 
> with "push_front< S, A >", otherwise top-level sequence cannot be a list.
> 
> Second, while recursive implementation is very similar to the iterative, 
> it still generates the combinations in reverse order :)  Not important 
> for applications I can think of, but still.
> 
> Finally, the performance comparison. I did it with GCC 4.2 on an Intel 
> dual core with 4G RAM running 64-bit Ubuntu Gutsy.

I just uploaded to boost vault, in 'Template Metaprogramming' directory,
an n-ary cross product which uses the binary one (or really a slight
modification) which I posted on the wiki earlier.  It uses
mpl::fold and the binary and joint_view to implement the
n-ary cross product.  I doubt it's as efficient as your
iterative one, but it might provide some more ideas for
other implementations.  If you post your benchmark, I could
actually make a comparison.

Anyway, the partial output is:

===>Enter:{{test3
   size_type=12
   cross_nproduct_view<Domains>
   { row_column_view
     size=4
     { 30002
     , 2001
     , 101
     , 0
     }
   , row_column_view
     size=4
     { 30002
     , 2001
     , 100
     , 0
     }
   , row_column_view
     size=4
     { 30002
     , 2000
     , 101
     , 0
     }
   , row_column_view
...

which has nicely indented output produced by some private
code.  Since you don't have that, you can switch it off
by #undef'ing  INDENT_PRINT.