1 files changed, 106 insertions, 0 deletions
diff --git a/src/gen_inverse.h b/src/gen_inverse.h
new file mode 100644
index 0000000..49f8ed0
--- /dev/null
+++ b/src/gen_inverse.h
@@ -0,0 +1,106 @@
+/* generic inverse of a function.
+
+Copyright 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Free Software Foundation, Inc.
+Contributed by the AriC and Caramel projects, INRIA.
+
+This file is part of the GNU MPFR Library.
+
+The GNU MPFR Library is free software; you can redistribute it and/or modify
+it under the terms of the GNU Lesser General Public License as published by
+the Free Software Foundation; either version 3 of the License, or (at your
+option) any later version.
+
+The GNU 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 Lesser General Public
+License for more details.
+
+You should have received a copy of the GNU Lesser General Public License
+along with the GNU MPFR Library; see the file COPYING.LESSER.  If not, see
+http://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc.,
+51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. */
+
+#define MPFR_NEED_LONGLONG_H
+#include "mpfr-impl.h"
+
+#ifndef ACTION_SPECIAL
+#define ACTION_SPECIAL
+#endif
+
+#ifndef ACTION_TINY
+#define ACTION_TINY
+#endif
+
+/* example of use:
+#define FUNCTION mpfr_sec
+#define INVERSE  mpfr_cos
+#define ACTION_NAN(y) do { MPFR_SET_NAN(y); MPFR_RET_NAN; } while (1)
+#define ACTION_INF(y) do { MPFR_SET_NAN(y); MPFR_RET_NAN; } while (1)
+#define ACTION_ZERO(y) return mpfr_set_ui (y, 1, MPFR_RNDN)
+#include "gen_inverse.h"
+*/
+
+int
+FUNCTION (mpfr_ptr y, mpfr_srcptr x, mpfr_rnd_t rnd_mode)
+{
+  mpfr_prec_t precy; /* target precision */
+  mpfr_prec_t m;     /* working precision */
+  mpfr_t z;        /* temporary variable to store INVERSE(x) */
+  int inexact;     /* inexact flag */
+  MPFR_ZIV_DECL (loop);
+  MPFR_SAVE_EXPO_DECL (expo);
+
+  if (MPFR_UNLIKELY(MPFR_IS_SINGULAR(x)))
+    {
+      if (MPFR_IS_NAN(x))
+        ACTION_NAN(y);
+      else if (MPFR_IS_INF(x))
+        ACTION_INF(y);
+      else /* x = 0 */
+        ACTION_ZERO(y,x);
+    }
+
+  /* x is neither NaN, Inf nor zero */
+  MPFR_SAVE_EXPO_MARK (expo);
+  ACTION_TINY (y, x, rnd_mode); /* special case for very small input x */
+  precy = MPFR_PREC(y);
+  m = precy + MPFR_INT_CEIL_LOG2 (precy) + 3;
+  mpfr_init2 (z, m);
+
+  MPFR_ZIV_INIT (loop, m);
+  for(;;)
+    {
+      MPFR_BLOCK_DECL (flags);
+
+      MPFR_BLOCK (flags, INVERSE (z, x, MPFR_RNDZ)); /* error k_u < 1 ulp */
+      /* FIXME: the following assumes that if an overflow happens with
+         MPFR_EMAX_MAX, then necessarily an underflow happens with
+         __gmpfr_emin */
+      if (MPFR_OVERFLOW (flags))
+        {
+          int s = MPFR_SIGN(z);
+          MPFR_ZIV_FREE (loop);
+          mpfr_clear (z);
+          MPFR_SAVE_EXPO_FREE (expo);
+          return mpfr_underflow (y, (rnd_mode == MPFR_RNDN) ?
+                                 MPFR_RNDZ : rnd_mode, s);
+        }
+      mpfr_ui_div (z, 1, z, MPFR_RNDN);
+      /* the error is less than c_w + 2*c_u*k_u (see algorithms.tex),
+         where c_w = 1/2, c_u = 1 since z was rounded toward zero,
+         thus 1/2 + 2 < 4 */
+      if (MPFR_LIKELY (MPFR_CAN_ROUND (z, m - 2, precy, rnd_mode)))
+        break;
+      ACTION_SPECIAL;
+      MPFR_ZIV_NEXT (loop, m);
+      mpfr_set_prec (z, m);
+    }
+  MPFR_ZIV_FREE (loop);
+
+  inexact = mpfr_set (y, z, rnd_mode);
+  mpfr_clear (z);
+
+ end:
+  MPFR_SAVE_EXPO_FREE (expo);
+  return mpfr_check_range (y, inexact, rnd_mode);
+}