add const version of as<T>

src/shogun/base/SGObject.h

@@ -492,36 +492,51 @@ class CSGObject
 	 */
 	std::vector<std::string> parameter_names() const;
 
-	/**
-	 * Utility method to specialize the feature to the required type.
+	/** Specializes a provided object to the specified type.
+	 * Throws exception if the object cannot be specialized.
 	 *
-	 * @param sgo CSGObject base type
-	 * @return The requested type if casting was successful.
+	 * @param sgo object of CSGObject base type
+	 * @return The requested type
 	 */
 	template<class T> static T* as(CSGObject* sgo)
 	{
 		REQUIRE(sgo, "No object provided!\n");
 		return sgo->as<T>();
 	}
 
-	/**
-	 * Utility method to specialize the feature to the required type.
+	/** Specializes the object to the specified type.
+	 * Throws exception if the object cannot be specialized.
 	 *
-	 * @param sgo CSGObject base type
-	 * @return The requested type if casting was successful, or throws exception.
+	 * @return The requested type
 	 */
 	template<class T> T* as()
 	{
-		T* c = dynamic_cast<T*>(this);
+		auto c = dynamic_cast<T*>(this);
 		if (c)
 			return c;
 
-		SG_SERROR("The object (%s) cannot be casted to the requested type %s!\n",
+		SG_SERROR("Object of type %s cannot be converted to type %s.\n",
 			demangled_type<std::remove_pointer_t<decltype(this)>>().c_str(),
 			demangled_type<T>().c_str());
 		return nullptr;
 	}
 
+	/** Specializes the object to the specified type.
+	 * Throws exception if the object cannot be specialized.
+	 *
+	 * @return The requested type
+	 */
+	template<class T> const T* as() const
+	{
+		auto c = dynamic_cast<const T*>(this);
+		if (c)
+			return c;
+
+		SG_SERROR("Object of type %s cannot be converted to type %s.\n",
+			demangled_type<std::remove_pointer_t<decltype(this)>>().c_str(),
+			demangled_type<T>().c_str());
+		return nullptr;
+	}
 #ifndef SWIG
 	/**
 	  * Get parameters observable