new implementation of mpfr_sin, using mpfr_cos

git-svn-id: svn://scm.gforge.inria.fr/svn/mpfr/trunk@1169 280ebfd0-de03-0410-8827-d642c229c3f4

1 files changed, 85 insertions, 0 deletions

diff --git a/sin.c b/sin.c
new file mode 100644
index 000000000..cbe76e2c8
--- /dev/null
+++ b/sin.c
@@ -0,0 +1,85 @@
+/* mpfr_sin -- sine of a floating-point number
+
+Copyright (C) 2001 Free Software Foundation.
+
+This file is part of the MPFR Library.
+
+The MPFR Library is free software; you can redistribute it and/or modify
+it under the terms of the GNU Library General Public License as published by
+the Free Software Foundation; either version 2 of the License, or (at your
+option) any later version.
+
+The MPFR Library is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Library General Public
+License for more details.
+
+You should have received a copy of the GNU Library General Public License
+along with the MPFR Library; see the file COPYING.LIB.  If not, write to
+the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+MA 02111-1307, USA. */
+
+#include <stdio.h>
+#include "gmp.h"
+#include "gmp-impl.h"
+#include "mpfr.h"
+#include "mpfr-impl.h"
+
+int 
+#if __STDC__
+mpfr_sin (mpfr_ptr y, mpfr_srcptr x, mp_rnd_t rnd_mode) 
+#else
+mpfr_sin (y, x, rnd_mode)
+     mpfr_ptr y;
+     mpfr_srcptr x;
+     mp_rnd_t rnd_mode;
+#endif
+{
+  int precy, m, ok, e;
+  mpfr_t c;
+
+  if (MPFR_IS_NAN(x) || MPFR_IS_INF(x))
+    {
+      MPFR_SET_NAN(y);
+      return 1; /* inexact */
+    }
+
+  if (!MPFR_NOTZERO(x))
+    {
+      mpfr_set_ui(y, 0, GMP_RNDN);
+      return 0; /* exact */
+    }
+
+  precy = MPFR_PREC(y);
+  m = precy + _mpfr_ceil_log2 ((double) precy) + ABS(MPFR_EXP(x)) + 13;
+
+  mpfr_init2 (c, m);
+
+  do
+    {
+      mpfr_cos (c, x, GMP_RNDZ);
+      mpfr_mul (c, c, c, GMP_RNDU);
+      mpfr_ui_sub (c, 1, c, GMP_RNDN);
+      e = 2 + (-MPFR_EXP(c)) / 2;
+      mpfr_sqrt (c, c, GMP_RNDN);
+      if (mpfr_cmp_ui (x, 0) < 0)
+	mpfr_neg (c, c, GMP_RNDN);
+
+      /* the absolute error on c is at most 2^(e-m) = 2^(EXP(c)-err) */
+      e = MPFR_EXP(c) + m - e;
+      ok = (e >= 0) && mpfr_can_round (c, e, GMP_RNDN, rnd_mode, precy);
+
+      if (ok == 0)
+	{
+	  m += BITS_PER_MP_LIMB;
+	  mpfr_set_prec (c, m);
+	}
+    }
+  while (!ok);
+
+  mpfr_set (y, c, rnd_mode);
+
+  mpfr_clear (c);
+
+  return 1; /* inexact */
+}