added new function mpfr_get_q

git-svn-id: svn://scm.gforge.inria.fr/svn/mpfr/trunk@11563 280ebfd0-de03-0410-8827-d642c229c3f4

8 files changed, 176 insertions, 2 deletions

diff --git a/NEWS b/NEWS
index dae7adc31..1b9e6cb0a 100644
--- a/NEWS
+++ b/NEWS
@@ -49,6 +49,7 @@ Changes from versions 3.1.* to version 4.0.0:
 - New functions mpfr_log_ui to compute the logarithm of an integer,
   mpfr_gamma_inc for the incomplete Gamma function, and mpfr_beta for the
   Beta function.
+- New function mpfr_get_q to convert a floating-point number into rational.
 - The mpfr_eint function now returns the value of the E1/eint1 function
   for negative argument.
 - The behavior of the mpfr_set_exp function changed, as it could easily
diff --git a/doc/mpfr.texi b/doc/mpfr.texi
index 66c62f433..00e86ec97 100644
--- a/doc/mpfr.texi
+++ b/doc/mpfr.texi
@@ -1565,6 +1565,12 @@ when it is smaller than @var{op}; moreover, if @var{rop} differs from
 @var{op}, i.e., if @var{op} is not an integer, the inexact flag is set.
 @end deftypefun
 
+@deftypefun void mpfr_get_q (mpq_t @var{rop}, mpfr_t @var{op}, mpfr_rnd_t)
+Convert @var{op} to a @code{mpq_t}.
+If @var{op} is NaN or an infinity, the @emph{erange} flag is
+set, @var{rop} is set to 0. Otherwise the conversion is always exact.
+@end deftypefun
+
 @deftypefun int mpfr_get_f (mpf_t @var{rop}, mpfr_t @var{op}, mpfr_rnd_t @var{rnd})
 Convert @var{op} to a @code{mpf_t}, after rounding it with respect to
 @var{rnd}.
diff --git a/src/Makefile.am b/src/Makefile.am
index c002950b6..5ec64760c 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -60,7 +60,7 @@ scale2.c set_z_exp.c ai.c gammaonethird.c ieee_floats.h			\
 grandom.c fpif.c set_float128.c get_float128.c rndna.c nrandom.c        \
 random_deviate.h random_deviate.c erandom.c mpfr-mini-gmp.c             \
 mpfr-mini-gmp.h fmma.c log_ui.c gamma_inc.c ubf.c invert_limb.h 	\
-invsqrt_limb.h beta.c odd_p.c
+invsqrt_limb.h beta.c odd_p.c get_q.c
 
 libmpfr_la_LIBADD = @LIBOBJS@
 
diff --git a/src/get_q.c b/src/get_q.c
new file mode 100644
index 000000000..c332880ba
--- /dev/null
+++ b/src/get_q.c
@@ -0,0 +1,53 @@
+/* mpfr_get_q -- get a multiple-precision rational from
+                 a floating-point number
+
+Copyright 2004, 2006-2017 Free Software Foundation, Inc.
+Contributed by the AriC and Caramba 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. */
+
+#include "mpfr-impl.h"
+
+/* part of the code was copied from get_z.c */
+void
+mpfr_get_q (mpq_ptr q, mpfr_srcptr f)
+{
+  mpfr_exp_t exp;
+  mpz_ptr u = mpq_numref (q);
+  mpz_ptr v = mpq_denref (q);
+
+  
+  mpz_set_ui (v, 1);
+  if (MPFR_UNLIKELY (MPFR_IS_SINGULAR (f)))
+    {
+      if (MPFR_UNLIKELY (MPFR_NOTZERO (f)))
+        MPFR_SET_ERANGEFLAG ();
+      mpz_set_ui (u, 0);
+      /* The ternary value is 0 even for infinity. Giving the rounding
+         direction in this case would not make much sense anyway, and
+         the direction would not necessarily match rnd. */
+    }
+  else
+    {
+      exp = mpfr_get_z_2exp (u, f);
+      if (exp >= 0)
+        mpz_mul_2exp (u, u, exp);
+      else
+        mpz_mul_2exp (v, v, -exp);
+    }
+}
diff --git a/src/mpf2mpfr.h b/src/mpf2mpfr.h
index b08964166..3ecbdf97b 100644
--- a/src/mpf2mpfr.h
+++ b/src/mpf2mpfr.h
@@ -176,5 +176,7 @@ http://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc.,
 
 #undef mpz_set_f
 #define mpz_set_f(z,f) mpfr_get_z(z,f,MPFR_DEFAULT_RND)
+#undef mpq_set_f
+#define mpq_set_f(q,f) mpfr_get_q(q,f)
 
 #endif /* __MPFR_FROM_MPF__ */
diff --git a/src/mpfr.h b/src/mpfr.h
index c54d24aca..421e53de1 100644
--- a/src/mpfr.h
+++ b/src/mpfr.h
@@ -475,6 +475,7 @@ __MPFR_DECLSPEC unsigned long mpfr_get_ui (mpfr_srcptr, mpfr_rnd_t);
 __MPFR_DECLSPEC char * mpfr_get_str (char*, mpfr_exp_t*, int, size_t,
                                      mpfr_srcptr, mpfr_rnd_t);
 __MPFR_DECLSPEC int mpfr_get_z (mpz_ptr z, mpfr_srcptr f, mpfr_rnd_t);
+__MPFR_DECLSPEC void mpfr_get_q (mpq_ptr q, mpfr_srcptr f);
 
 __MPFR_DECLSPEC void mpfr_free_str (char *);
 
diff --git a/tests/Makefile.am b/tests/Makefile.am
index f2c0502a6..772196e8f 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -33,7 +33,7 @@ check_PROGRAMS = tversion tabort_prec_max tassert tabort_defalloc1	\
      tsprintf tsqr tsqrt tsqrt_ui tstckintc tstdint tstrtofr tsub	\
      tsub1sp tsub_d tsub_ui tsubnormal tsum tswap ttan ttanh ttrunc	\
      tui_div tui_pow tui_sub turandom tvalist ty0 ty1 tyn tzeta		\
-     tzeta_ui tbeta
+     tzeta_ui tbeta tget_q
 
 # Before Automake 1.13, we ran tversion at the beginning and at the end
 # of the tests, and output from tversion appeared at the same place as
diff --git a/tests/tget_q.c b/tests/tget_q.c
new file mode 100644
index 000000000..0bafd4817
--- /dev/null
+++ b/tests/tget_q.c
@@ -0,0 +1,111 @@
+/* Test file for mpfr_get_q.
+
+Copyright 2017 Free Software Foundation, Inc.
+Contributed by the AriC and Caramba 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. */
+
+#include "mpfr-test.h"
+
+static void
+special (void)
+{
+  mpfr_t f;
+  mpq_t q;
+
+  mpfr_init2 (f, MPFR_PREC_MIN);
+  mpq_init (q);
+
+  /* check NaN */
+  mpfr_set_nan (f);
+  mpfr_clear_erangeflag ();
+  mpfr_get_q (q, f);
+  MPFR_ASSERTN(mpq_cmp_ui (q, 0, 1) == 0);
+  MPFR_ASSERTN(mpfr_erangeflag_p ());
+
+  /* check +Inf */
+  mpfr_set_inf (f, 1);
+  mpfr_clear_erangeflag ();
+  mpfr_get_q (q, f);
+  MPFR_ASSERTN(mpq_cmp_ui (q, 0, 1) == 0);
+  MPFR_ASSERTN(mpfr_erangeflag_p ());
+
+  /* check -Inf */
+  mpfr_set_inf (f, -1);
+  mpfr_clear_erangeflag ();
+  mpfr_get_q (q, f);
+  MPFR_ASSERTN(mpq_cmp_ui (q, 0, 1) == 0);
+  MPFR_ASSERTN(mpfr_erangeflag_p ());
+
+  /* check +0 */
+  mpfr_set_zero (f, 1);
+  mpfr_clear_erangeflag ();
+  mpfr_get_q (q, f);
+  MPFR_ASSERTN(mpq_cmp_ui (q, 0, 1) == 0);
+  MPFR_ASSERTN(!mpfr_erangeflag_p ());
+
+  /* check -0 */
+  mpfr_set_zero (f, -1);
+  mpfr_clear_erangeflag ();
+  mpfr_get_q (q, f);
+  MPFR_ASSERTN(mpq_cmp_ui (q, 0, 1) == 0);
+  MPFR_ASSERTN(!mpfr_erangeflag_p ());
+
+  mpq_clear (q);
+  mpfr_clear (f);
+}
+
+static void
+random_tests (void)
+{
+  mpfr_t f, g;
+  mpq_t q;
+  int inex;
+  mpfr_rnd_t rnd;
+  int i;
+
+  mpfr_init2 (f, MPFR_PREC_MIN + (randlimb() % 100));
+  mpfr_init2 (g, mpfr_get_prec (f));
+  mpq_init (q);
+
+  for (i = 0; i < 1000; i++)
+    {
+      mpfr_urandomb (f, RANDS);
+      mpfr_get_q (q, f);
+      rnd = RND_RAND ();
+      inex = mpfr_set_q (g, q, rnd);
+      MPFR_ASSERTN(inex == 0);
+      MPFR_ASSERTN(mpfr_cmp (f, g) == 0);
+    }
+
+  mpq_clear (q);
+  mpfr_clear (f);
+  mpfr_clear (g);
+}
+
+int
+main (void)
+{
+  tests_start_mpfr ();
+
+  special ();
+  random_tests ();
+
+  tests_end_mpfr ();
+  return 0;
+}