1 files changed, 49 insertions, 0 deletions
diff --git a/winsup/mingw/mingwex/complex/catan.c b/winsup/mingw/mingwex/complex/catan.c
new file mode 100644
index 000000000..eee1e8fa7
--- /dev/null
+++ b/winsup/mingw/mingwex/complex/catan.c
@@ -0,0 +1,49 @@
+/* catan.c */
+
+/*
+   Contributed by Danny Smith
+   2003-10-17
+
+   FIXME: This needs some serious numerical analysis.
+*/
+
+#include <math.h>
+#include <complex.h>
+#include <errno.h>
+
+/* catan (z) = -I/2 * clog ((I + z) / (I - z)) */ 
+
+double complex 
+catan (double complex Z)
+{
+  double complex Res;
+  double complex Tmp;
+  double x = __real__ Z;
+  double y = __imag__ Z;
+
+  if ( x == 0.0 && (1.0 - fabs (y)) == 0.0)
+    {
+      errno = ERANGE;
+      __real__ Res = HUGE_VAL;
+      __imag__ Res = HUGE_VAL;
+    }
+   else if (isinf (_hypot (x, y)))
+   {
+     __real__ Res = (x > 0 ? M_PI_2 : -M_PI_2);
+     __imag__ Res = 0.0;
+   }
+  else
+    {
+      __real__ Tmp = - x; 
+      __imag__ Tmp = 1.0 - y;
+
+      __real__ Res = x; 
+      __imag__ Res = y + 1.0;
+
+      Tmp = clog (Res/Tmp);	
+      __real__ Res  = - 0.5 * __imag__ Tmp;
+      __imag__ Res =  0.5 * __real__ Tmp;
+    }
+
+   return Res; 
+}