Takes fn by forwarding ref. in for_each_pair, resolves #4148

Author: daniel-j-h

include/util/for_each_pair.hpp

@@ -3,6 +3,7 @@
 
 #include <iterator>
 #include <numeric>
+#include <utility>
 
 namespace osrm
 {
@@ -12,31 +13,30 @@ namespace util
 // TODO: check why this is not an option here:
 // std::adjacent_find(begin, end, [=](const auto& l, const auto& r){ return function(), false; });
 template <typename ForwardIterator, typename Function>
-Function for_each_pair(ForwardIterator begin, ForwardIterator end, Function function)
+void for_each_pair(ForwardIterator begin, ForwardIterator end, Function &&function)
 {
     if (begin == end)
     {
-        return function;
+        return;
     }
 
     auto next = begin;
     next = std::next(next);
 
     while (next != end)
     {
-        function(*begin, *next);
+        std::forward<Function>(function)(*begin, *next);
         begin = std::next(begin);
         next = std::next(next);
     }
-    return function;
 }
 
 template <class ContainerT, typename Function>
-Function for_each_pair(ContainerT &container, Function function)
+void for_each_pair(ContainerT &container, Function &&function)
 {
     using std::begin;
     using std::end;
-    return for_each_pair(begin(container), end(container), function);
+    for_each_pair(begin(container), end(container), std::forward<Function>(function));
 }
 
 } // namespace util