From 269c380c745529788a2bd15b159d0aa232b2dc9e Mon Sep 17 00:00:00 2001
From: Daniel Langesten <daniel.langest@gmail.com>
Date: Wed, 11 Mar 2015 10:19:00 +0100
Subject: avoiding division by zero and negative numbers and som comments
 describing the function

---
 diffpriv.go | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/diffpriv.go b/diffpriv.go
index 03f341f..382ef37 100644
--- a/diffpriv.go
+++ b/diffpriv.go
@@ -10,7 +10,14 @@ var (
 	rnd = rand.New(rand.NewSource(time.Now().UnixNano()))
 )
 
+//Returns 0 if epsilon is less than or equal to 0.
+//Otherwise it picks a number from the laplace distribution
+//with the mean 0 and standard deviation sensitivity/epsilon.
+//This follows the definition of differential privacy noise addition.
 func diffpriv(value int, sensitivity, epsilon float64) int {
+	if epsilon <= 0 {
+		return 0
+	}
 	noise := laplaceDist(0, sensitivity/epsilon)
 	return round(float64(value) + noise)
 }
-- 
cgit v1.1