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.