1 files changed, 59 insertions, 0 deletions
diff --git a/contrib/libf2c/libF77/z_log.c b/contrib/libf2c/libF77/z_log.c
new file mode 100644
index 0000000..f56b12e
--- /dev/null
+++ b/contrib/libf2c/libF77/z_log.c
@@ -0,0 +1,59 @@
+#include "f2c.h"
+
+#undef abs
+#include "math.h"
+extern double f__cabs (double, double);
+void
+z_log (doublecomplex * r, doublecomplex * z)
+{
+  double s, s0, t, t2, u, v;
+  double zi = z->i, zr = z->r;
+
+  r->i = atan2 (zi, zr);
+#ifdef Pre20000310
+  r->r = log (f__cabs (zr, zi));
+#else
+  if (zi < 0)
+    zi = -zi;
+  if (zr < 0)
+    zr = -zr;
+  if (zr < zi)
+    {
+      t = zi;
+      zi = zr;
+      zr = t;
+    }
+  t = zi / zr;
+  s = zr * sqrt (1 + t * t);
+  /* now s = f__cabs(zi,zr), and zr = |zr| >= |zi| = zi */
+  if ((t = s - 1) < 0)
+    t = -t;
+  if (t > .01)
+    r->r = log (s);
+  else
+    {
+
+#ifdef Comment
+
+      log (1 + x) = x - x ^ 2 / 2 + x ^ 3 / 3 - x ^ 4 / 4 + -...
+	= x (1 - x / 2 + x ^ 2 / 3 - +...)
+	[sqrt (y ^ 2 + z ^ 2) - 1] *[sqrt (y ^ 2 + z ^ 2) + 1] =
+	y ^ 2 + z ^ 2 - 1, so sqrt (y ^ 2 + z ^ 2) - 1 =
+	(y ^ 2 + z ^ 2 - 1) /[sqrt (y ^ 2 + z ^ 2) + 1]
+#endif /*Comment */
+	t = ((zr * zr - 1.) + zi * zi) / (s + 1);
+      t2 = t * t;
+      s = 1. - 0.5 * t;
+      u = v = 1;
+      do
+	{
+	  s0 = s;
+	  u *= t2;
+	  v += 2;
+	  s += u / v - t * u / (v + 1);
+	}
+      while (s > s0);
+      r->r = s * t;
+    }
+#endif
+}