ceph/src/boost/libs/histogram/examples/guide_histogram_in_api.cpp

   1 // Copyright 2020 Hans Dembinski
   2 //
   3 // Distributed under the Boost Software License, Version 1.0.
   4 // (See accompanying file LICENSE_1_0.txt
   5 // or copy at http://www.boost.org/LICENSE_1_0.txt)
   6
   7 //[ guide_histogram_in_api
   8
   9 #include <boost/histogram.hpp>
  10 #include <cassert>
  11
  12 // function accepts any histogram and returns a copy
  13 template <class Axes, class Storage>
  14 boost::histogram::histogram<Axes, Storage> any_histogram(
  15     boost::histogram::histogram<Axes, Storage>& h) {
  16   return h;
  17 }
  18
  19 // function only accepts histograms with fixed axis types and returns a copy
  20 template <class Storage, class... Axes>
  21 boost::histogram::histogram<std::tuple<Axes...>, Storage> only_static_histogram(
  22     boost::histogram::histogram<std::tuple<Axes...>, Storage>& h) {
  23   return h;
  24 }
  25
  26 // function only accepts histograms with dynamic axis types and returns a copy
  27 template <class Storage, class... Axes>
  28 boost::histogram::histogram<std::vector<boost::histogram::axis::variant<Axes...>>,
  29                             Storage>
  30 only_dynamic_histogram(
  31     boost::histogram::histogram<std::vector<boost::histogram::axis::variant<Axes...>>,
  32                                 Storage>& h) {
  33   return h;
  34 }
  35
  36 int main() {
  37   using namespace boost::histogram;
  38
  39   auto histogram_with_static_axes = make_histogram(axis::regular<>(10, 0, 1));
  40
  41   using axis_variant = axis::variant<axis::regular<>, axis::integer<>>;
  42   std::vector<axis_variant> axes;
  43   axes.emplace_back(axis::regular<>(5, 0, 1));
  44   axes.emplace_back(axis::integer<>(0, 1));
  45   auto histogram_with_dynamic_axes = make_histogram(axes);
  46
  47   assert(any_histogram(histogram_with_static_axes) == histogram_with_static_axes);
  48   assert(any_histogram(histogram_with_dynamic_axes) == histogram_with_dynamic_axes);
  49   assert(only_static_histogram(histogram_with_static_axes) == histogram_with_static_axes);
  50   assert(only_dynamic_histogram(histogram_with_dynamic_axes) ==
  51          histogram_with_dynamic_axes);
  52
  53   // does not compile: only_static_histogram(histogram_with_dynamic_axes)
  54   // does not compile: only_dynamic_histogram(histogram_with_static_axes)
  55 }
  56
  57 //]