Add wrapped histogram example to getting started section

doc/getting_started.qbk

@@ -64,4 +64,13 @@ The library was designed to work well with the C++ standard library. Here is an
 
 [endsect]
 
+[section Making classes that hold histograms]
+
+The histograms get their great flexibility and performance from being templated, but this can make the types a bit cumbersome to write. Often it is possible to use `auto` to let the compiler deduce the type, but when you want to store histograms in a class, you need to write the type explicitly. The next example shows how this works. 
+
+[import ../examples/getting_started_listing_05.cpp]
+[getting_started_listing_05]
+
+[endsect]
+
 [endsect]

examples/Jamfile

@@ -21,6 +21,7 @@ alias cxx14 :
     [ run getting_started_listing_02.cpp ]
     [ run getting_started_listing_03.cpp ]
     [ run getting_started_listing_04.cpp ]
+    [ run getting_started_listing_05.cpp ]
     [ run guide_axis_basic_demo.cpp ]
     [ run guide_axis_circular.cpp ]
     [ run guide_axis_growing.cpp ]

examples/getting_started_listing_05.cpp

@@ -0,0 +1,65 @@
+// Copyright 2019 Hans Dembinski
+//
+// Distributed under the Boost Software License, Version 1.0.
+// (See accompanying file LICENSE_1_0.txt
+// or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+// clang-format off
+
+//[ getting_started_listing_05
+
+//////////////// Begin: put this in header file ////////////////////
+
+#include <algorithm>           // std::max_element
+#include <boost/format.hpp>    // only needed for printing
+#include <boost/histogram.hpp> // make_histogram, integer, indexed
+#include <iostream>            // std::cout, std::endl
+#include <sstream>             // std::ostringstream
+#include <tuple>
+#include <vector>
+
+// use this when axis configuration is fix to get highest performance
+struct HolderOfStaticHistogram {
+  // put axis types here
+  using axes_t = std::tuple<
+    boost::histogram::axis::regular<>,
+    boost::histogram::axis::integer<>    
+  >;
+  using hist_t = boost::histogram::histogram<axes_t>;
+  hist_t hist_;
+};
+
+// use this when axis configuration should be flexible
+struct HolderOfDynamicHistogram {
+  // put all axis types here that you are going to use
+  using axis_t = boost::histogram::axis::variant<
+    boost::histogram::axis::regular<>,
+    boost::histogram::axis::variable<>,    
+    boost::histogram::axis::integer<>    
+  >;
+  using axes_t = std::vector<axis_t>;
+  using hist_t = boost::histogram::histogram<axes_t>;
+  hist_t hist_;
+};
+
+//////////////// End: put this in header file ////////////////////
+
+int main() {
+  using namespace boost::histogram;
+
+  HolderOfStaticHistogram hs;
+  hs.hist_ = make_histogram(axis::regular<>(5, 0, 1), axis::integer<>(0, 3));
+  // now assign a different histogram
+  hs.hist_ = make_histogram(axis::regular<>(3, 1, 2), axis::integer<>(4, 6));
+  // hs.hist_ = make_histogram(axis::regular<>(5, 0, 1)); does not work;
+  // the static histogram cannot change the number or order of axis types
+
+  HolderOfDynamicHistogram hd;
+  hd.hist_ = make_histogram(axis::regular<>(5, 0, 1), axis::integer<>(0, 3));
+  // now assign a different histogram
+  hd.hist_ = make_histogram(axis::regular<>(3, -1, 2));
+  // and assign another
+  hd.hist_ = make_histogram(axis::integer<>(0, 5), axis::integer<>(3, 5));
+}
+
+//]