2014/1/5 Brian Davis <bitminer@gmail.com>

Is there a 1 line wonder for counting iterator and back_inserter - say a counting iterator where the start and step can be specified?

The following code creates an vector of angles from zero to N-1 * angle step;

std::vector angles;
float angle_step = 0.275;
int number_angles = 293;

std::copy(
boost::counting_iterator<float>(0),
boost::counting_iterator<float>(number_angles),
std::back_inserter(angles) );

std::copy(
boost::make_transform_iterator(angles.begin(), boost::bind1st(std::multiplies<float>(), angle_step )),
boost::make_transform_iterator(angles.end(), boost::bind1st(std::multiplies<float>(), angle_step )),
angles.begin() );

Is there or could there be a counting iterator or other mechanism to do this in 1 line?
Say where the start and step could be specified?

Thanks

I recommend Boost.Range. In your example I also suggest using Boost.Phoenix instead of bind1st and multiplies; and push_back from Boost.Range instead of back_inserter.

#include <boost/phoenix/core.hpp>

#include <boost/phoenix/operator.hpp>

#include <boost/range/irange.hpp>

#include <boost/range/adaptor/transformed.hpp>

#include <boost/range/algorithm/copy.hpp>

#include <boost/range/algorithm_ext/push_back.hpp>

#include <iostream>

#include <iterator>

#include <vector>

using namespace boost::phoenix::placeholders;

namespace ad = boost::adaptors;

static int const N = 10;

static float const STEP = 0.5;

int main()

{

std::vector<float> x, y;

boost::copy( boost::irange(0,N) | ad::transformed( _1 * STEP ), std::back_inserter(x) );

boost::push_back( y, boost::irange(0,N) | ad::transformed( _1 * STEP ) );

boost::copy( x, std::ostream_iterator<float>(std::cout, " ") );

std::cout << std::endl;

boost::copy( y, std::ostream_iterator<float>(std::cout, " ") );

std::cout << std::endl;

}

Regards,

Kris