On Fri, Oct 28, 2011 at 9:28 PM, Dave Abrahams <dave@boostpro.com> wrote:
on Thu Oct 27 2011, Fernando Pelliccioni <fpelliccioni-AT-gmail.com> wrote:
Is there interest in adding a Top-Bounded adaptor into Boost.Range ?
Example:
using namespace boost::adaptors; using namespace boost::assign;
std::vector<int> input; input += 1,2,3,4,5,6,7,8,9;
boost::copy( input | bounded(0), std::ostream_iterator<int>(std::cout, ",")); // prints nothing boost::copy( input | bounded(1), std::ostream_iterator<int>(std::cout, ",")); // prints 1, boost::copy( input | bounded(2), std::ostream_iterator<int>(std::cout, ",")); // prints 1,2, boost::copy( input | bounded(8), std::ostream_iterator<int>(std::cout, ",")); // prints 1,2,3,4,5,7,8,
Is there interest in this for Boost?
There is an obvious generalization that stops the range when a predicate is satisfied, e.g.
boost::copy( input | until(_1 == 8), std::ostream_iterator<int>(std::cout, ","));
That leads me to believe that the proper behavior of the less-generalized component, which you call "bounded," is to stop the range when the element reaches the bound, rather than including it.
I think I have explained incorrectly. The above example is not appropriate. What I want to achieve ( using ranges ) is the following... //------------------------------------------------------- #include <iostream> #include <vector> #include <boost/assign.hpp> #include <boost/range/adaptors.hpp> int main() { using namespace boost::adaptors; using namespace boost::assign; std::vector<int> input; input += 0,1,1,2,3,5,8,13,21,34,55; auto it = boost::begin(input); auto end = boost::end(input); const int N = 9; // top bound for ( int i = 0; it != end && i < N; ++it, ++i ) { std::cout << *it << ','; // or whatever ... } } //------------------------------------------------------- // prints: 0,1,1,2,3,5,8,13,21, // ( 9 elements ) Similar to the algorithm *copy_n*, with the difference that *copy_n*doesn't check the end of the iterator. Perhaps "bound" isn't the best name, there should be a better name, maybe "top" ... I dont know... Could this behavior be replicated with other adaptors? Is the "until" adaptor part of Boost? Regards, Fernando.