added sum algorithm

test/algorithm_sum_test.cpp

@@ -0,0 +1,46 @@
+// 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)
+
+#include <boost/core/lightweight_test.hpp>
+#include <boost/histogram.hpp>
+#include <boost/histogram/algorithm/sum.hpp>
+#include "utility_histogram.hpp"
+
+using namespace boost::histogram;
+using namespace boost::histogram::literals; // to get _c suffix
+using boost::histogram::algorithm::sum;
+
+template <typename Tag>
+void run_tests() {
+  auto ax = axis::integer<>(0, 100);
+
+  auto h1 = make(Tag(), ax);
+  for (unsigned i = 0; i < 100; ++i) h1(i);
+  BOOST_TEST_EQ(sum(h1), 100);
+
+  auto h2 = make_s(Tag(), std::vector<double>(), ax, ax);
+  for (unsigned i = 0; i < 100; ++i)
+    for (unsigned j = 0; j < 100; ++j) h2(i, j);
+
+  BOOST_TEST_EQ(sum(h2), 100000);
+
+  auto h3 = make_s(Tag(), std::array<int, 102>(), ax);
+  for (unsigned i = 0; i < 100; ++i) h3(i);
+
+  BOOST_TEST_EQ(sum(h3), 100);
+
+  auto h4 = make_s(Tag(), std::unordered_map<std::size_t, int>(), ax);
+  for (unsigned i = 0; i < 100; ++i) h3(i);
+
+  BOOST_TEST_EQ(sum(h3), 100);
+}
+
+int main() {
+  run_tests<static_tag>();
+  run_tests<dynamic_tag>();
+
+  return boost::report_errors();
+}