[NL] TS; constify isSolutionErrorComputationNeeded

NumLib/TimeStepping/Algorithms/EvolutionaryPIDcontroller.h

@@ -80,7 +80,7 @@ public:
         _is_accepted = accepted;
     }
 
-    bool isSolutionErrorComputationNeeded() override { return true; }
+    bool isSolutionErrorComputationNeeded() const override { return true; }
 
     virtual bool canReduceTimestepSize() const override;
 

NumLib/TimeStepping/Algorithms/IterationNumberBasedTimeStepping.h

@@ -97,7 +97,7 @@ public:
     bool accepted() const override;
     void setAcceptedOrNot(bool accepted) override { _accepted = accepted; };
 
-    bool isSolutionErrorComputationNeeded() override { return true; }
+    bool isSolutionErrorComputationNeeded() const override { return true; }
 
     bool canReduceTimestepSize() const override;
 

NumLib/TimeStepping/Algorithms/TimeStepAlgorithm.h

@@ -111,7 +111,7 @@ public:
 
     /// Get a flag to indicate whether this algorithm needs to compute
     /// solution error. The default return value is false.
-    virtual bool isSolutionErrorComputationNeeded() { return false; }
+    virtual bool isSolutionErrorComputationNeeded() const { return false; }
 
     /// Query the timestepper if further time step size reduction is possible.
     virtual bool canReduceTimestepSize() const { return false; }