From f05d7b4d4f051db1a268269b2de063be140dcd03 Mon Sep 17 00:00:00 2001
From: fdai7848 <jan.heidekrueger@informatik.hs-fulda.de>
Date: Fri, 2 Feb 2024 19:21:36 +0100
Subject: [PATCH] add support to ln function for larger numbers

---
 src/exponent.c    |  4 +++-
 src/logarithmus.c | 43 +++++++++++++++++++++++++++++++++----------
 2 files changed, 36 insertions(+), 11 deletions(-)

diff --git a/src/exponent.c b/src/exponent.c
index 9873ad3..0904080 100644
--- a/src/exponent.c
+++ b/src/exponent.c
@@ -1,5 +1,6 @@
 #include <stdio.h>
 #include <limits.h>
+#include <stdbool.h>
 
 #include "exponent.h"
 #include "logarithmus.h"
@@ -63,9 +64,10 @@ unsigned long long fac(int x){
 
 double exponential(double x){
     double sum = 0.0;
-    for(int i = 0; i<=21; i++){
+    for(int i = 0; i<=20; i++){
         sum += (1.0/fac(i)*(powerD(i,x)));
     }
+    
     return sum;
 }
 
diff --git a/src/logarithmus.c b/src/logarithmus.c
index 8dbfd7a..9bd265d 100644
--- a/src/logarithmus.c
+++ b/src/logarithmus.c
@@ -8,7 +8,7 @@ double logX(double b, double a){
     if(b == 1.0 || b <= 0.0 || a <= 0.0){
         return -1.0;
     }
-    return(logN(a, 0.000001)/logN(b, 0.000001));
+    return(logN(a, 0.00000001)/logN(b, 0.00000001));
 }
 
 double logDec(double a){
@@ -22,14 +22,37 @@ double logBin(double a){
 double logN(double x, double eps){
     if(x <= 0){
         return -1.0;
-    }    
-    double yn = x - 1.0;
-    double yn1 = yn;
+    }
+    if(x<200){
+        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);
 
-    do{
-        yn = yn1;
-        yn1 = yn + 2 * (x - exponential(yn)) / (x + exponential(yn));
-    } while (absD(yn - yn1) > eps);
+        return yn1;
+    }
+    else{
+        int power_adjust = 0;
+        while (x > 1.0) {
+            x /= exponential(1);
+            power_adjust++;
+        }
+        while (x < .25) {
+            x *= exponential(1);
+            power_adjust--;
+        }
+        
+        x -= 1.0;
+        double t = 0.0, s = 1.0, z = x;
+        for (int k=1; k<=100; k++) {
+            t += z * s / k;
+            z *= x;
+            s = -s;
+        }
+        return t + power_adjust;
+    }    
+}
 
-    return yn1;
-}
\ No newline at end of file