From e6d64b939a78f3d18a34add5668e9364bcea83c4 Mon Sep 17 00:00:00 2001
From: Gregory Nutt <gnutt@nuttx.org>
Date: Mon, 8 Sep 2014 07:55:09 -0600
Subject: Correct atan2 implementations from Denis Arnst

---
 nuttx/libc/math/lib_atan2.c  | 48 +++++++++++++++----------------------------
 nuttx/libc/math/lib_atan2f.c | 48 +++++++++++++++----------------------------
 nuttx/libc/math/lib_atan2l.c | 49 +++++++++++++++-----------------------------
 3 files changed, 51 insertions(+), 94 deletions(-)

(limited to 'nuttx/libc')

diff --git a/nuttx/libc/math/lib_atan2.c b/nuttx/libc/math/lib_atan2.c
index f78484d39..5f4a6bff0 100644
--- a/nuttx/libc/math/lib_atan2.c
+++ b/nuttx/libc/math/lib_atan2.c
@@ -41,46 +41,32 @@
 #ifdef CONFIG_HAVE_DOUBLE
 double atan2(double y, double x)
 {
-  if (y == 0.0)
+  if (x > 0)
     {
-      if (x >= 0.0)
-        {
-          return 0.0;
-        }
-      else
-        {
-          return M_PI;
-        }
+      return atan(y / x);
     }
-  else if (y > 0.0)
+  else if (y >= 0 && x < 0)
     {
-      if (x == 0.0)
-        {
-          return M_PI_2;
-        }
-      else if (x > 0.0)
-        {
-          return atan(y / x);
-        }
-      else
-        {
-          return M_PI - atan(y / x);
-        }
+      return atan(y / x) + M_PI;
     }
-  else
+  else if (y < 0)
     {
-      if (x == 0.0)
-        {
-          return M_PI + M_PI_2;
-        }
-      else if (x > 0.0)
+      if (x == 0)
         {
-          return 2 * M_PI - atan(y / x);
+          return -M_PI_2;
         }
-      else
+      else /* Can only be x < 0 */
         {
-          return M_PI + atan(y / x);
+          return atan(y / x) - M_PI;
         }
     }
+  else if (y > 0 && x == 0)
+    {
+      return M_PI_2;
+    }
+  else if (y == 0 && x == 0) /* Undefined but returns normally 0 */
+    {
+      return 0;
+    }
 }
 #endif
diff --git a/nuttx/libc/math/lib_atan2f.c b/nuttx/libc/math/lib_atan2f.c
index f3a92ff53..999edd6ee 100644
--- a/nuttx/libc/math/lib_atan2f.c
+++ b/nuttx/libc/math/lib_atan2f.c
@@ -37,45 +37,31 @@
 
 float atan2f(float y, float x)
 {
-  if (y == 0.0)
+  if (x > 0)
     {
-      if (x >= 0.0)
-        {
-          return 0.0;
-        }
-      else
-        {
-          return M_PI;
-        }
+      return atanf(y / x);
     }
-  else if (y > 0.0)
+  else if (y >= 0 && x < 0)
     {
-      if (x == 0.0)
-        {
-          return M_PI_2;
-        }
-      else if (x > 0.0)
-        {
-          return atanf(y / x);
-        }
-      else
-        {
-          return M_PI - atanf(y / x);
-        }
+      return atanf(y / x) + M_PI;
     }
-  else
+  else if (y < 0)
     {
-      if (x == 0.0)
-        {
-          return M_PI + M_PI_2;
-        }
-      else if (x > 0.0)
+      if (x == 0)
         {
-          return 2 * M_PI - atanf(y / x);
+          return -M_PI_2;
         }
-      else
+      else /* Can only be x < 0 */
         {
-          return M_PI + atanf(y / x);
+          return atanf(y / x) - M_PI;
         }
     }
+  else if (y > 0 && x == 0)
+    {
+      return M_PI_2;
+    }
+  else if (y == 0 && x == 0) /* Undefined but returns normally 0 */
+    {
+      return 0;
+    }
 }
diff --git a/nuttx/libc/math/lib_atan2l.c b/nuttx/libc/math/lib_atan2l.c
index e2a576e58..1946a3f04 100644
--- a/nuttx/libc/math/lib_atan2l.c
+++ b/nuttx/libc/math/lib_atan2l.c
@@ -41,47 +41,32 @@
 #ifdef CONFIG_HAVE_LONG_DOUBLE
 long double atan2l(long double y, long double x)
 {
-
-  if (y == 0.0)
+  if (x > 0)
     {
-      if (x >= 0.0)
-        {
-          return 0.0;
-        }
-      else
-        {
-          return M_PI;
-        }
+      return atanl(y / x);
     }
-  else if (y > 0.0)
+  else if (y >= 0 && x < 0)
     {
-      if (x == 0.0)
-        {
-          return M_PI_2;
-        }
-      else if (x > 0.0)
-        {
-          return atanl(y / x);
-        }
-      else
-        {
-          return M_PI - atanl(y / x);
-        }
+      return atanl(y / x) + M_PI;
     }
-  else
+  else if (y < 0)
     {
-      if (x == 0.0)
-        {
-          return M_PI + M_PI_2;
-        }
-      else if (x > 0.0)
+      if (x == 0)
         {
-          return 2 * M_PI - atanl(y / x);
+          return -M_PI_2;
         }
-      else
+      else /* Can only be x < 0 */
         {
-          return M_PI + atanl(y / x);
+          return atanl(y / x) - M_PI;
         }
     }
+  else if (y > 0 && x == 0)
+    {
+      return M_PI_2;
+    }
+  else if (y == 0 && x == 0) /* Undefined but returns normally 0 */
+    {
+      return 0;
+    }
 }
 #endif
-- 
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