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tjp/core/math/mean.hpp

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+//
+//  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
+