ENH: Moved derivative methods to IDifferentiable class-interface, so that not...

ENH: Moved derivative methods to IDifferentiable class-interface, so that not all activation classes have to implement them now.

src/Neuron/Neuron.h

@@ -160,21 +160,6 @@ public:
      */
     virtual int activation_function_get_n_parameters();
 
-    /**
-     * Calculates the partial derivative of the activation function
-     * with respect to the parameter and the current potential
-     * @param[in] param_idx Index of the parameter to calculate derivative of
-     * @return Partial derivative of the activation function according to the
-     * 'param_idx'-th parameter
-     */
-    virtual double activation_function_get_partial_derivative(int param_idx) = 0;
-
-    /**
-     * Calculates the derivative with respect to the argument, ie the 'potential'
-     * @return f'(x), where 'f(x)' is the activation function and 'x' = 'potential'
-     */
-    virtual double activation_function_get_derivative( ) = 0;
-
     /**
      * Adjusts the parameter with index 'param_idx' of the activation function
      * by the value prescribed by 'value'
@@ -225,4 +210,25 @@ public:
 }; /* end of Neuron class */
 
 
-#endif /* NEURON_H_ */
\ No newline at end of file
+/**
+ * Class serving as an interface providing 'activation_function_get_partial_derivative'
+ * and 'activation_function_get_derivative' methods.
+ */
+class IDifferentiable {
+    /**
+     * Calculates the partial derivative of the activation function
+     * with respect to the parameter and the current potential
+     * @param[in] param_idx Index of the parameter to calculate derivative of
+     * @return Partial derivative of the activation function according to the
+     * 'param_idx'-th parameter
+     */
+    virtual double activation_function_get_partial_derivative(int param_idx) = 0;
+
+    /**
+     * Calculates the derivative with respect to the argument, ie the 'potential'
+     * @return f'(x), where 'f(x)' is the activation function and 'x' = 'potential'
+     */
+    virtual double activation_function_get_derivative( ) = 0;
+}; /* end of IDifferentiable class */
+
+ #endif /* NEURON_H_ */
\ No newline at end of file

src/Neuron/NeuronLinear.h

@@ -16,7 +16,7 @@
  * Linear neuron class - uses activation function in the form f(x)=a*x + b,
  * 'x' being the neuron's potential
  */
-class NeuronLinear:public Neuron {
+class NeuronLinear:public Neuron, public IDifferentiable {
     friend class boost::serialization::access;
 
 protected:

src/Neuron/NeuronLogistic.h

@@ -14,7 +14,7 @@
 #include "Neuron.h"
 #include "../constants.h"
 
-class NeuronLogistic:public Neuron {
+class NeuronLogistic:public Neuron, public IDifferentiable {
     friend class boost::serialization::access;
 
 protected:

src/Neuron/NeuronTanh.h

@@ -14,7 +14,7 @@
 #include "Neuron.h"
 #include "../constants.h"
 
-class NeuronTanh:public Neuron {
+class NeuronTanh:public Neuron, public IDifferentiable {
     friend class boost::serialization::access;
 
 protected: