From 1a7d4d2dc17087790c3e540d213fcc7dccc270d4 Mon Sep 17 00:00:00 2001
From: Ahmet Inan <inan@aicodix.de>
Date: Sat, 3 Mar 2018 12:14:22 +0100
Subject: [PATCH] added same() method to Kahan summation

same() returns true if added value doesn't change the low or high values
---
 kahan.hh | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/kahan.hh b/kahan.hh
index a169d38..d096ab9 100644
--- a/kahan.hh
+++ b/kahan.hh
@@ -16,6 +16,7 @@ class Kahan
 public:
 	Kahan() : high(0), low(0) {}
 	Kahan(T init) : high(init), low(0) {}
+	Kahan(const Kahan &a) : high(a.high), low(a.low) {}
 #if __clang__
 	[[clang::optnone]]
 #elif __GNUC__
@@ -30,6 +31,16 @@ public:
 		low = (sum - high) - tmp;
 		return high = sum;
 	}
+	bool operator == (const Kahan &a)
+	{
+		return low == a.low && high == a.high;
+	}
+	bool same(T input)
+	{
+		Kahan tmp(*this);
+		(*this)(input);
+		return tmp == *this;
+	}
 	T operator ()() { return high; }
 };