Fixes instruction discarding in post-processing

src/engine/guidance/post_processing.cpp

@@ -4,6 +4,8 @@
 #include "engine/guidance/toolkit.hpp"
 
 #include <boost/assert.hpp>
+#include <boost/range/algorithm_ext/erase.hpp>
+
 #include <iostream>
 #include <vector>
 
@@ -237,18 +239,16 @@ std::vector<RouteStep> postProcess(std::vector<RouteStep> steps)
 
     // finally clean up the post-processed instructions.
     // Remove all, now NO_TURN instructions for the set of steps
-    auto pos = steps.begin();
-    for (auto check = steps.begin(); check != steps.end(); ++check)
+
+    // keep valid instructions
+    const auto not_is_valid = [](const RouteStep &step)
     {
-        // keep valid instrucstions
-        if (check->maneuver.instruction != TurnInstruction::NO_TURN() ||
-            check->maneuver.waypoint_type != WaypointType::None)
-        {
-            *pos = *check;
-            ++pos;
-        }
-    }
-    steps.erase(pos, steps.end());
+        return step.maneuver.instruction == TurnInstruction::NO_TURN() ||
+               step.maneuver.waypoint_type == WaypointType::None;
+    };
+
+    boost::remove_erase_if(steps, not_is_valid);
+
 #if PRINT_DEBUG
     std::cout << "Merged\n";
     print(steps);