Wow, we also have exp!

math/exp.c

@@ -0,0 +1,30 @@
+#include <math.h>
+
+#define TOLERANCE 0.0000001
+
+/*
+  A C adaptation of Dr. Ching-Kuang Shene's FORTRAN version
+  from https://pages.mtu.edu/~shene/COURSES/cs201/NOTES/chap04/exp.html
+
+  I was stuck on how to actually implement the Taylor series without it
+  getting far too big for even a long double, and I'm not sure I ever would
+  have thought to just break it out recursively like this. Instead of each
+  term being x^n/n!, this says that it's (x/n+1)*(nth term), with a base case
+  of x/1! = x. Pretty clever, really.
+
+  Also, really glad I know how to at least read a basic FORTRAN program. This
+  probably would have been a little more annoying if I didn't.
+
+  -Kat
+*/
+double exp(double x) {
+  double term = x;
+  double sum = 1.0;
+
+  for(int i = 1; fabs(term) > TOLERANCE; i++) {
+    sum += term;
+    term *= (x / i);
+  }
+
+  return sum;
+}