add boost on mac

macx64/include/boost/histogram/algorithm/sum.hpp

@@ -0,0 +1,41 @@
+// Copyright 2018 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)
+
+#ifndef BOOST_HISTOGRAM_ALGORITHM_SUM_HPP
+#define BOOST_HISTOGRAM_ALGORITHM_SUM_HPP
+
+#include <boost/histogram/accumulators/sum.hpp>
+#include <boost/histogram/fwd.hpp>
+#include <boost/mp11/utility.hpp>
+#include <numeric>
+#include <type_traits>
+
+namespace boost {
+namespace histogram {
+namespace algorithm {
+/** Compute the sum over all histogram cells, including underflow/overflow bins.
+
+  If the value type of the histogram is an integral or floating point type,
+  boost::accumulators::sum<double> is used to compute the sum, else the original value
+  type is used. Compilation fails, if the value type does not support operator+=.
+
+  Return type is double if the value type of the histogram is integral or floating point,
+  and the original value type otherwise.
+ */
+template <class A, class S>
+auto sum(const histogram<A, S>& h) {
+  using T = typename histogram<A, S>::value_type;
+  using Sum = mp11::mp_if<std::is_arithmetic<T>, accumulators::sum<double>, T>;
+  Sum sum;
+  for (auto x : h) sum += x;
+  using R = mp11::mp_if<std::is_arithmetic<T>, double, T>;
+  return static_cast<R>(sum);
+}
+} // namespace algorithm
+} // namespace histogram
+} // namespace boost
+
+#endif