#ifndef EXPONENTIAL_H
#define EXPONENTIAL_H

#include <cmath>
#include <random>
#include "../random/RandomGenerator.h"

namespace Distribution {

	/** exponential distribution */
	template <typename T> class Exponential {

	private:

		const T lambda;

        Random::RandomGenerator gen;
		std::exponential_distribution<T> dist;

	public:

		/** ctor */
		Exponential(const T lambda) : lambda(lambda), gen(RANDOM_SEED), dist(lambda) {
			;
		}

		/** get probability for the given value */
		T getProbability(const T val) const {
			return getProbability(lambda, val);
		}

		/** get an exponentially distributed random number */
		T draw() {
			return dist(gen);
		}

		/** set the seed to use */
		void setSeed(const long seed) {
			gen.seed(seed);
		}


		/** get the probability for the given value */
		static T getProbability(const T lambda, const T val) {
			return (val < 0) ? (0) : (lambda * std::exp( -lambda * val ));
		}

	};

}

#endif // EXPONENTIAL_H