1 files changed, 58 insertions, 2 deletions
diff --git a/buch/papers/0f1/listings/potenzreihe.c b/buch/papers/0f1/listings/potenzreihe.c
index bfaa0e3..23fdfea 100644
--- a/buch/papers/0f1/listings/potenzreihe.c
+++ b/buch/papers/0f1/listings/potenzreihe.c
@@ -1,12 +1,68 @@
 #include <math.h>
 
-static double powerseries(const double b, const double z, unsigned int n)
+/**
+  * @brief Calculates pochhammer
+  * @param (a+n-1)!
+  * @return Result
+  */
+static double pochhammer(const double x, double n)
+{
+    double temp = x;
+
+    if (n > 0)
+    {
+        while (n > 1)
+        {
+            temp *= (x + n - 1);
+            --n;
+        }
+
+        return temp;
+    }
+    else
+    {
+        return 1;
+    }
+}
+
+/**
+  * @brief Calculates the Factorial
+  * @param n!
+  * @return Result
+  */
+static double fac(int n)
+{
+    double temp = n;
+
+    if (n > 0)
+    {
+        while (n > 1)
+        {
+            --n;
+            temp *= n;
+        }
+        return temp;
+    }
+    else
+    {
+        return 1;
+    }
+}
+
+/**
+  * @brief Calculates the Hypergeometric Function 0F1(;b;z)
+  * @param c in 0F1(;c;z)
+  * @param z in 0F1(;c;z)
+  * @param n number of itertions (precision)
+  * @return Result
+  */
+static double powerseries(const double c, const double z, unsigned int n)
 {
     double temp = 0.0;
 
     for (unsigned int k = 0; k < n; ++k)
     {
-        temp += pow(z, k) / (factorial(k) * pochhammer(b, k));
+        temp += pow(z, k) / (factorial(k) * pochhammer(c, k));
     }
 
     return temp;