wrote function for generation of values in a laplace distribution

1 files changed, 21 insertions, 2 deletions

diff --git a/diffpriv.go b/diffpriv.go
index 22e844f..8b945d3 100644
--- a/diffpriv.go
+++ b/diffpriv.go
@@ -1,5 +1,24 @@
 package main
 
-func laplaceDist(u, b int) int {
-	return 4 //chosen by fair laplance weighted diceroll
+import (
+	"math/rand"
+)
+
+// Returns a random value from a laplace
+// distribution with parameters u and b.
+func laplaceDist(u, b float64) float64 {
+	uniform := rand.Float64()
+	uniform -= 0.5
+	return u - b*sgn(uniform)*math.Log(1-2*math.Abs(uniform))
+}
+
+// The signum function
+func sgn(x float64) flot64 {
+	if x < 0 {
+		return -1
+	}
+	if x > 0 {
+		return 1
+	}
+	return 0
 }