//
//  Math.hpp
//  amoeba
//
//  Created by Timothy Prepscius on 12/30/16.
//  Copyright © 2016 Timothy Prepscius. All rights reserved.
//

#pragma once

namespace tjp::core::math {

template<typename T>
struct Mean_SumDivide
{
	T t = zero<T>();
	size_t count = 0;
	
	void add(const T &v)
	{
		t = t + v;
		count++;
	}
	
	T mean() const
	{
		return t / count;
	}
};

// https://www.geeksforgeeks.org/program-for-average-of-an-array-without-running-into-overflow/
template<typename T>
struct Mean_AddDivide
{
	T t = zero<T>();
	size_t count = 0;
	
	void add(const T &v)
	{
		++count;
		t = t + (v - t) / (count);
	}
	
	T mean() const
	{
		return t / count;
	}
} ;

// https://www.geeksforgeeks.org/compute-average-two-numbers-without-overflow/
template<typename T>
struct Mean_AddDivideMod
{
	T t = zero<T>();
	size_t count = 0;
	
	void add(const T &v)
	{
		++count;
		t = t + (v - t) / (count);
	}
	
	T mean() const
	{
		return t / count;
	}
} ;

template<typename T, typename U>
auto mean_(const U &u)
{
	T t;
	for (auto &v: u)
		t.add(v);
	
	return t.mean();
}

template<typename U>
auto mean(const U &u)
{
	return mean_<Mean_SumDivide<typename U::value_type>>(u);
}

} // namespace