Clean up qualifiers

src/nicefunction.hh

@@ -38,9 +38,9 @@ class TrivialFunction : public NiceFunction {
 public:
   void virtual evaluate(double const& x, double& y) const { y = 0; }
 
-  double virtual leftDifferential(const double) const { return 0; }
+  double virtual leftDifferential(double) const { return 0; }
 
-  double virtual rightDifferential(const double) const { return 0; }
+  double virtual rightDifferential(double) const { return 0; }
 };
 
 // slope in [n-1,n] is n