import newlib-2000-02-17 snapshot

1 files changed, 140 insertions, 0 deletions

diff --git a/newlib/libm/mathfp/sf_atangent.c b/newlib/libm/mathfp/sf_atangent.c
new file mode 100644
index 000000000..55a90063c
--- /dev/null
+++ b/newlib/libm/mathfp/sf_atangent.c
@@ -0,0 +1,140 @@
+
+/* @(#)z_atangentf.c 1.0 98/08/13 */
+/******************************************************************
+ * The following routines are coded directly from the algorithms
+ * and coefficients given in "Software Manual for the Elementary
+ * Functions" by William J. Cody, Jr. and William Waite, Prentice
+ * Hall, 1980.
+ ******************************************************************/
+/******************************************************************
+ * Arctangent
+ *
+ * Input:
+ *   x - floating point value
+ *
+ * Output:
+ *   arctangent of x
+ *
+ * Description:
+ *   This routine calculates arctangents.
+ *
+ *****************************************************************/
+
+#include <float.h>
+#include "fdlibm.h"
+#include "zmath.h"
+
+static const float ROOT3 = 1.732050807;
+static const float a[] = { 0.0, 0.523598775, 1.570796326,
+                     1.047197551 };
+static const float q[] = { 0.1412500740e+1 };
+static const float p[] = { -0.4708325141, -0.5090958253e-1 };
+
+float
+_DEFUN (atangentf, (float, float, float, int),
+        float x _AND
+        float v _AND
+        float u _AND
+        int arctan2)
+{
+  float f, g, R, P, Q, A, res;
+  int N;
+  int branch = 0;
+  int expv, expu;
+
+  /* Preparation for calculating arctan2. */
+  if (arctan2)
+    {
+      if (u == 0.0)
+        if (v == 0.0)
+          {
+            errno = ERANGE;
+            return (z_notanum_f.f);
+          }
+        else
+          {
+            branch = 1;
+            res = __PI_OVER_TWO;
+          }
+
+      if (!branch)
+        {
+          int e;
+          /* Get the exponent values of the inputs. */
+          g = frexpf (v, &expv);
+          g = frexpf (u, &expu);
+
+          /* See if a divide will overflow. */
+          e = expv - expu;
+          if (e > FLT_MAX_EXP)
+            {
+               branch = 1;
+               res = __PI_OVER_TWO;
+            }
+
+          /* Also check for underflow. */
+          else if (e < FLT_MIN_EXP)
+            {
+               branch = 2;
+               res = 0.0;
+            }
+         }
+    }
+
+  if (!branch)
+    {
+      if (arctan2)
+        f = fabsf (v / u);
+      else
+        f = fabsf (x);
+
+      if (f > 1.0)
+        {
+          f = 1.0 / f;
+          N = 2;
+        }
+      else
+        N = 0;
+
+      if (f > (2.0 - ROOT3))
+        {
+          A = ROOT3 - 1.0;
+          f = (((A * f - 0.5) - 0.5) + f) / (ROOT3 + f);
+          N++;
+        }
+
+      /* Check for values that are too small. */
+      if (-z_rooteps_f < f && f < z_rooteps_f)
+        res = f;
+
+      /* Calculate the Taylor series. */
+      else
+        {
+          g = f * f;
+          P = (p[1] * g + p[0]) * g;
+          Q = g + q[0];
+          R = P / Q;
+
+          res = f + f * R;
+        }
+
+      if (N > 1)
+        res = -res;
+
+      res += a[N];
+    }
+
+  if (arctan2)
+    {
+      if (u < 0.0 || branch == 2)
+        res = __PI - res;
+      if (v < 0.0 || branch == 1)
+        res = -res;
+    }
+  else if (x < 0.0)
+    {
+      res = -res;
+    }
+
+  return (res);
+}