#pragma once

#include <string>

namespace NeuralNetwork {
namespace ActivationFunction {

	/**
	* @author Tomas Cernik (Tom.Cernik@gmail.com)
	* @brief Abstract class of activation function
	*/
	class ActivationFunction {
		public:

			virtual ~ActivationFunction() {}

			/**
			 * @brief Returns derivation of output, it is slower than version with output as it needs to compute output
			 * @param input is input of function
			 */
			inline float derivatedOutput(const float &input) {
				return derivatedOutput(input,operator()(input));
			};

			/**
			 * @brief Returns derivation of output
			 * @param input is input of function
			 * @param output is output of function
			 * @see derivatedOutput
			 */
			virtual float derivatedOutput(const float &input, const float &output) =0;

			/**
			 * @brief Returns value of output
			 * @param x is input of function
			 */
			virtual float operator()(const float &x)=0;

			/**
			 * @brief Function returns clone of object
			 */
			virtual ActivationFunction* clone() const = 0;

			/**
			 * @brief This is a virtual function for storing Activation function
			 * @returns json describing function
			 */
			virtual std::string stringify() const =0;
	};
}
}