1 files changed, 44 insertions, 0 deletions
diff --git a/src/math/exp.c b/src/math/exp.c
new file mode 100644
index 00000000..b63ecf4f
--- /dev/null
+++ b/src/math/exp.c
@@ -0,0 +1,44 @@
+# define TGSOURCE "exp.c"
+#include <math.h>
+#include "nonstd/tgmath.h"
+#include "errno.h"
+
+/** exponential function **/
+TYPE TGFN(exp)(TYPE x)
+{
+	int MAXLOOPS = 10;
+	int i;
+	int factorial = 1;
+	TYPE exponent = 1.0;
+	TYPE power = 1.0;
+
+	if (0) {
+		errno = ERANGE; /* The magnitude of ARGUMENT(x) is too large */
+		/* RETURN_FAILURE(CONSTANT(HUGE_VAL), A range error occurred); */
+		return TGHUGE;
+	}
+
+	/* TODO: tweak max loops */
+
+	/* exp x = 1 + x + x^2/2! + x^3/3! + x^4/4! ... */
+	for (i = 1; i < MAXLOOPS; i++) {
+		power *= x;
+		factorial *= i;
+		exponent += power / factorial;
+	}
+
+	/* RETURN_SUCCESS(the exponential function of ARGUMENT(x)); */
+	return exponent;
+}
+
+/***
+compute the exponential function of ARGUMENT(x).
+***/
+
+/*
+IMPLEMENTATION(The value returned on a domain error, CONSTANT(HUGE_VAL))
+LINK(m)
+*/
+/*
+STDC(1)
+*/