added activation functions

machine/activation.cpp

@@ -0,0 +1,15 @@
+#include <cmath>
+#include "activation.h"
+
+using std::exp;
+using std::pow;
+
+namespace Activations {
+  double relu(double x){
+    return x <= 0 ? 0 : x;
+  }
+
+  double sigmoid(double x){
+    return pow((1 + exp(-x)), -1);
+  }
+}

machine/activation.h

@@ -0,0 +1,6 @@
+#pragma  once
+
+namespace Activations {
+  double relu(double x);
+  double sigmoid(double x);
+}

machine/layer.cpp

@@ -3,23 +3,28 @@
 
 using Matrices::Matrix;
 using std::invalid_argument;
+using std::invalid_argument;
 
 namespace Layers {
+  bool input;
   unsigned int size;
   Matrix *values;
+  double (*activation)(double);
 
-  Layer::Layer(unsigned int size){
+  Layer::Layer(unsigned int size, bool input){
     this->size = size;
     this->values = new Matrix(size, 1);
     this->values->random(-1, 1);
+    this->input = input;
   }
 
-  Layer::Layer(Matrix *values){
+  Layer::Layer(Matrix *values, bool input){
     if(values->get_height() != 1)
       throw invalid_argument("Invalid values dimensions!");
 
     this->size = values->get_width();
     this->values = values;
+    this->input = input;
   }
 
   Matrix* Layer::get_values(){
@@ -33,4 +38,22 @@ namespace Layers {
   unsigned int Layer::get_size() const {
     return this->size;
   }
+
+  void Layer::set_activation_function(double (*activation)(double)){
+    if(this->input)
+      invalid_argument("Input layer must not have a activation function!");
+
+    this->activation = activation; 
+  }
+
+  void Layer::activate_neurons(){
+    double *neurons = this->values->get_row(0);
+
+    for(unsigned int i = 0; i < this->size; i++){
+      double neuron_value = neurons[i];
+      this->values->update_value(i, 0, this->activation(neuron_value));
+    }
+
+    delete neurons;
+  }
 }

machine/layer.h

@@ -7,14 +7,18 @@ using Matrices::Matrix;
 namespace Layers{
   class Layer{
     public:
-      Layer(unsigned int size);
-      Layer(Matrix *values);
+      Layer(unsigned int size, bool input=false);
+      Layer(Matrix *values, bool input=false);
       Matrix* get_values();
       unsigned int get_size() const;
       ~Layer();
+      void set_activation_function(double (*activation)(double));
+      void activate_neurons();
     private:
       unsigned int size;
+      bool input = false;
       Matrix *values;
+      double (*activation)(double);
   };
 
 };

machine/machine.cpp

@@ -78,4 +78,5 @@ namespace Machine {
     for(Weights *weight: (*this->weights))
       delete weight;
   }
+
 }