Use nested namespace

It's a mechanical change to modernize the code base

include/engine/map_matching/bayes_classifier.hpp

@@ -8,11 +8,7 @@
 
 #include <boost/math/constants/constants.hpp>
 
-namespace osrm
-{
-namespace engine
-{
-namespace map_matching
+namespace osrm::engine::map_matching
 {
 
 struct NormalDistribution
@@ -98,8 +94,6 @@ class BayesClassifier
     double positive_apriori_probability;
     double negative_apriori_probability;
 };
-} // namespace map_matching
-} // namespace engine
 } // namespace osrm
 
 #endif // BAYES_CLASSIFIER_HPP

include/engine/map_matching/hidden_markov_model.hpp

@@ -11,11 +11,7 @@
 #include <limits>
 #include <vector>
 
-namespace osrm
-{
-namespace engine
-{
-namespace map_matching
+namespace osrm::engine::map_matching
 {
 
 static const double log_2_pi = std::log(2. * boost::math::constants::pi<double>());
@@ -137,8 +133,6 @@ template <class CandidateLists> struct HiddenMarkovModel
         return initial_timestamp;
     }
 };
-} // namespace map_matching
-} // namespace engine
 } // namespace osrm
 
 #endif // HIDDEN_MARKOV_MODEL

include/engine/map_matching/matching_confidence.hpp

@@ -5,11 +5,7 @@
 
 #include <cmath>
 
-namespace osrm
-{
-namespace engine
-{
-namespace map_matching
+namespace osrm::engine::map_matching
 {
 
 struct MatchingConfidence
@@ -51,8 +47,6 @@ struct MatchingConfidence
   private:
     ClassifierT classifier;
 };
-} // namespace map_matching
-} // namespace engine
 } // namespace osrm
 
 #endif

include/engine/map_matching/sub_matching.hpp

@@ -5,11 +5,7 @@
 
 #include <vector>
 
-namespace osrm
-{
-namespace engine
-{
-namespace map_matching
+namespace osrm::engine::map_matching
 {
 
 struct SubMatching
@@ -19,8 +15,6 @@ struct SubMatching
     std::vector<unsigned> alternatives_count;
     double confidence;
 };
-} // namespace map_matching
-} // namespace engine
 } // namespace osrm
 
 #endif