Re: [Boost-users] Iterators for the cartesian product

13 Jun 2011


      On 06/13/11 15:06, kelvSYC wrote:
...
On Jun 13, 2011, at 8:19 AM, Larry Evans wrote:
...
On 06/13/11 06:37, kelvSYC wrote:
...
So that the wheel doesn't have to be reinvented if it's already out
there, is there something in boost that will take a bunch of
sequences (lists, say) and return a sequence containing the
cartesian product all of them, either as a tuple or after applying a
function to them?
...
For example, is there something in boost that will, given a bunch of
lists of integers, return a list of integers formed by multiplying
together one member from each list?
To be more concrete, say you have:
std::vector<int> x({1,2,3});
 std::vector<int> y({4,5});
and what you want is something like:
std::vector z
 ( { {  4,  5}
   , {  8, 10}
   , { 12, 15}
   }
 };
Is that about right?
No, just a straight up cartesian product.
The example I provided was meant to be an example of, as you say,
"applying a function to them".  In my example, that would be
the std::multiply<int>() functor.  The "straight up cartesian product"
would be produced by using std::make_pair as the function.
...
So I'd want z to be equal to
std::vector({{1,4}, {1,5}, {2,4}, {2,5}, {3,4}, {3,5}});
Is there something in boost that will give me this sequence (or at least iterators therein?)
I pretty sure there is none since the thread I mentioned previously did
not mention one and people replying to that thread indicated it would
be desirable.

-regards,
Larry