ADD: added a new neuron to represent a never-changing shift of the input values

src/Neuron/NeuronBiased.cpp

+/**
+ * DESCRIPTION OF THE FILE
+ *
+ * @author Michal Kravčenko
+ * @date 15.3.19 -
+ */
+
+#include "NeuronBiased.h"
+#include "NeuronConstant.h"
+
+namespace lib4neuro{
+
+    NeuronBiased::NeuronBiased(double b) {
+        this->bias = b;
+    }
+
+    double NeuronBiased::activate(double x, double b) {
+        return x + this->bias;
+    }
+
+    double NeuronBiased::activation_function_eval_derivative(double x, double b) {
+        return 1.0;
+    }
+
+    double NeuronBiased::activation_function_eval_derivative_bias(double x, double b) {
+        return 0.0;
+    }
+
+    Neuron* NeuronBiased::get_derivative() {
+        NeuronConstant *output = new NeuronConstant(1.0);
+        return output;
+    }
+
+}//end of namespace lib4neuro
\ No newline at end of file

src/Neuron/NeuronBiased.h

+/**
+ * DESCRIPTION OF THE FILE
+ *
+ * @author Michal Kravčenko
+ * @date 15.3.19 -
+ */
+
+#ifndef LIB4NEURO_NEURONBIASED_H
+#define LIB4NEURO_NEURONBIASED_H
+
+#include "Neuron.h"
+
+namespace lib4neuro {
+    class NeuronBiased: public NeuronDifferentiable {
+
+    private:
+
+        double bias;
+
+    public:
+
+        /**
+         * Struct used to access private properties from
+         * the serialization function
+         */
+        struct access;
+
+        /**
+         * Constructs the object of the Linear neuron with activation function
+         * f(x) = x + b
+         * @param[in] b Bias
+         */
+        LIB4NEURO_API explicit NeuronBiased( double b );
+
+        /**
+         * Evaluates 'x + this->bias' and stores the result into the 'state' property
+         */
+        LIB4NEURO_API double activate( double x, double b ) override;
+
+        /**
+         * Calculates the partial derivative of the activation function
+         * f(x) = x + this->bias at point x
+         * @return Partial derivative of the activation function according to the
+         * 'bias' parameter. Returns 0.0
+         */
+        LIB4NEURO_API double activation_function_eval_derivative_bias( double x, double b ) override;
+
+        /**
+         * Calculates d/dx of (x + this->bias) at point x
+         * @return 1.0
+         */
+        LIB4NEURO_API double activation_function_eval_derivative( double x, double b ) override;
+
+        /**
+         * Returns a pointer to a Neuron with derivative as its activation function
+         * @return
+         */
+        LIB4NEURO_API Neuron* get_derivative( ) override;
+    };
+
+}//end of namespace lib4neuro
+
+#endif //LIB4NEURO_NEURONBIASED_H