samer@10: function h=product_it(f,g)
samer@10: % product_it- compose two iterators to run in parallel
samer@10: %
samer@10: % product_it::
samer@10: %    iterator(A) ~'first iterator transformer and initial value',
samer@10: %    iterator(B) ~'second iterator transformer and initial value',
samer@10: % -> iterator(cell {A,B}) ~'combined iterator'.
samer@10: %
samer@10: % The state transformer function returns [] to signal termination
samer@10: % if EITHER of the sub-transformer functions returns [].
samer@10: 
samer@10:    ff=f{1}; gg=g{1};
samer@10:    h={@prodit,{f{2},g{2}}};
samer@10: 
samer@10:    function h=prodit(s)
samer@10:       s1=ff(s{1});
samer@10:       s2=gg(s{2});
samer@10:       if isempty(s1) || isempty(s2)
samer@10:          h=[];
samer@10:       else
samer@10:          h={s1,s2};
samer@10:       end
samer@10:    end
samer@10: end
samer@10: