From 79c38646875acdb2146bde63c9f16fbcc023cc8c Mon Sep 17 00:00:00 2001
From: fdai7848 <jan.heidekrueger@informatik.hs-fulda.de>
Date: Wed, 31 Jan 2024 10:35:43 +0100
Subject: [PATCH] implement first revision for ln with halley-newton-approx

---
 src/exponent.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/src/exponent.c b/src/exponent.c
index 2cfecf5..b37deab 100644
--- a/src/exponent.c
+++ b/src/exponent.c
@@ -46,4 +46,24 @@ double exponential(double x){
         sum += (1.0/fac(i)*(expIN(i,x)));
     }
     return sum;
+}
+
+double absD(double x){
+    if(x<0){
+        return -1 * x;
+    }
+    return x;
+}
+
+double logN(double x, double eps){
+    double yn = x - 1.0;
+    double yn1 = yn;
+
+    do
+    {
+        yn = yn1;
+        yn1 = yn + 2 * (x - exponential(yn)) / (x + exponential(yn));
+    } while (absD(yn - yn1) > eps);
+
+    return yn1;
 }
\ No newline at end of file