1 files changed, 114 insertions, 0 deletions
diff --git a/nuttx/libc/math/lib_sin.c b/nuttx/libc/math/lib_sin.c
new file mode 100644
index 000000000..e005d98cb
--- /dev/null
+++ b/nuttx/libc/math/lib_sin.c
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+/************************************************************************
+ * libc/math/lib_sin.c
+ *
+ * This file is a part of NuttX:
+ *
+ *   Copyright (C) 2012 Gregory Nutt. All rights reserved.
+ *   Ported by: Darcy Gong
+ *
+ * It derives from the Rhombs OS math library by Nick Johnson which has
+ * a compatibile, MIT-style license:
+ *
+ * Copyright (C) 2009-2011 Nick Johnson <nickbjohnson4224 at gmail.com>
+ * 
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ * 
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ ************************************************************************/
+
+/************************************************************************
+ * Included Files
+ ************************************************************************/
+
+#include <nuttx/config.h>
+#include <nuttx/compiler.h>
+
+#include <sys/types.h>
+#include <math.h>
+
+#ifdef CONFIG_HAVE_DOUBLE
+
+/************************************************************************
+ * Private Data
+ ************************************************************************/
+
+static double _dbl_inv_fact[] =
+{
+  1.0 / 1.0,                    // 1 / 1!
+  1.0 / 6.0,                    // 1 / 3!
+  1.0 / 120.0,                  // 1 / 5!
+  1.0 / 5040.0,                 // 1 / 7!
+  1.0 / 362880.0,               // 1 / 9!
+  1.0 / 39916800.0,             // 1 / 11!
+  1.0 / 6227020800.0,           // 1 / 13!
+  1.0 / 1307674368000.0,        // 1 / 15!
+  1.0 / 355687428096000.0,      // 1 / 17!
+  1.0 / 121645100408832000.0,   // 1 / 19!
+};
+
+/************************************************************************
+ * Public Functions
+ ************************************************************************/
+
+double sin(double x)
+{
+  double x_squared;
+  double sin_x;
+  size_t i;
+
+  /* Move x to [-pi, pi) */
+
+  x = fmod(x, 2 * M_PI);
+  if (x >= M_PI)
+    {
+      x -= 2 * M_PI;
+    }
+
+  if (x < -M_PI)
+    {
+      x += 2 * M_PI;
+    }
+
+  /* Move x to [-pi/2, pi/2) */
+
+  if (x >= M_PI_2)
+    {
+      x = M_PI - x;
+    }
+
+  if (x < -M_PI_2)
+    {
+      x = -M_PI - x;
+    }
+
+  x_squared = x * x;
+  sin_x = 0.0;
+
+  /* Perform Taylor series approximation for sin(x) with ten terms */
+
+  for (i = 0; i < 10; i++)
+    {
+      if (i % 2 == 0)
+        {
+          sin_x += x * _dbl_inv_fact[i];
+        }
+      else
+        {
+          sin_x -= x * _dbl_inv_fact[i];
+        }
+
+      x *= x_squared;
+    }
+
+  return sin_x;
+}
+#endif