Added thirdparty: boost library

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

@@ -0,0 +1,68 @@
+// 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/histogram/indexed.hpp>
+#include <boost/mp11/utility.hpp>
+#include <type_traits>
+
+namespace boost {
+namespace histogram {
+namespace algorithm {
+
+/** Compute the sum over all histogram cells (underflow/overflow included by default).
+
+  The implementation favors accuracy and protection against overflow over speed. If the
+  value type of the histogram is an integral or floating point type,
+  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+=. The return type
+  is double if the value type of the histogram is integral or floating point, and the
+  original value type otherwise.
+
+  If you need a different trade-off, you can write your own loop or use `std::accumulate`:
+  ```
+  // iterate over all bins
+  auto sum_all = std::accumulate(hist.begin(), hist.end(), 0.0);
+
+  // skip underflow/overflow bins
+  double sum = 0;
+  for (auto&& x : indexed(hist))
+    sum += *x; // dereference accessor
+
+  // or:
+  // auto ind = boost::histogram::indexed(hist);
+  // auto sum = std::accumulate(ind.begin(), ind.end(), 0.0);
+  ```
+
+  @returns accumulator type or double
+
+  @param hist Const reference to the histogram.
+  @param cov  Iterate over all or only inner bins (optional, default: all).
+*/
+template <class A, class S>
+auto sum(const histogram<A, S>& hist, const coverage cov = coverage::all) {
+  using T = typename histogram<A, S>::value_type;
+  // T is arithmetic, compute sum accurately with high dynamic range
+  using sum_type = mp11::mp_if<std::is_arithmetic<T>, accumulators::sum<double>, T>;
+  sum_type sum;
+  if (cov == coverage::all)
+    for (auto&& x : hist) sum += x;
+  else
+    // sum += x also works if sum_type::operator+=(const sum_type&) exists
+    for (auto&& x : indexed(hist)) 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