//[ guide_access_bin_counts

#include <boost/histogram.hpp>
#include <iostream>
#include <numeric>

namespace bh = boost::histogram;

int main() {
  // make histogram with 2 x 2 = 4 bins (not counting under-/overflow bins)
  auto h = bh::make_static_histogram(bh::axis::regular<>(2, -1, 1),
                                     bh::axis::regular<>(2, 2, 4));

  h(bh::weight(1), -0.5, 2.5); // bin index 0, 0
  h(bh::weight(2), -0.5, 3.5); // bin index 0, 1
  h(bh::weight(3), 0.5, 2.5);  // bin index 1, 0
  h(bh::weight(4), 0.5, 3.5);  // bin index 1, 1

  // access count value, number of indices must match number of axes
  std::cout << h.at(0, 0).value() << " " << h.at(0, 1).value() << " "
            << h.at(1, 0).value() << " " << h.at(1, 1).value() << std::endl;

  // prints: 1 2 3 4

  // access count variance, number of indices must match number of axes
  std::cout << h.at(0, 0).variance() << " " << h.at(0, 1).variance() << " "
            << h.at(1, 0).variance() << " " << h.at(1, 1).variance()
            << std::endl;
  // prints: 1 4 9 16

  // this is more efficient when you want to query value and variance
  auto c11 = h.at(1, 1);
  std::cout << c11.value() << " " << c11.variance() << std::endl;
  // prints: 4 16

  // histogram also supports access via container; using a container of
  // wrong size trips an assertion in debug mode
  auto idx = {0, 1};
  std::cout << h.at(idx).value() << std::endl;
  // prints: 2

  // histogram also provides bin iterators
  auto sum = std::accumulate(h.begin(), h.end(),
                             typename decltype(h)::element_type(0));
  std::cout << sum.value() << " " << sum.variance() << std::endl;
  // prints: 10 30

  // bin iterators are fancy iterators with extra methods
  for (auto it = h.begin(), end = h.end(); it != end; ++it) {
    const auto x = *it;
    std::cout << it.idx(0) << " " << it.idx(1) << ": "
              << x.value() << " " << x.variance() << std::endl;
  }
  // prints: (iteration order is an implementation detail, don't rely on it)
  // 0 0: 1 1
  // 1 0: 3 9
  // ...
  // 2 -1: 0 0
  // -1 -1: 0 0
}

//]