1 files changed, 35 insertions, 0 deletions
diff --git a/lib/libm/catan.c b/lib/libm/catan.c
new file mode 100644
index 00000000..b6880811
--- /dev/null
+++ b/lib/libm/catan.c
@@ -0,0 +1,35 @@
+#include <float.h>
+#include "__complex.h"
+
+double complex catan(double complex z)
+{
+	double complex w;
+	double a, t, x, x2, y;
+
+	x = creal(z);
+	y = cimag(z);
+
+	if ((x == 0.0) && (y > 1.0))
+		goto overflow;
+
+	x2 = x * x;
+	a = 1.0 - x2 - (y * y);
+	if (a == 0.0)
+		goto overflow;
+
+	t = 0.5 * atan2(2.0 * x, a);
+	w = redupi(t);
+
+	t = y - 1.0;
+	a = x2 + (t * t);
+	if (a == 0.0)
+		goto overflow;
+
+	t = y + 1.0;
+	a = (x2 + (t * t)) / a;
+
+	return w + (0.25 * log(a)) * I;
+
+overflow:
+	return DBL_MAX + DBL_MAX * I;
+}