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diff --git a/mpfr/set_q.c b/mpfr/set_q.c
new file mode 100644
index 00000000..3422b7c6
--- /dev/null
+++ b/mpfr/set_q.c
@@ -0,0 +1,133 @@
+/* mpfr_set_q -- set a floating-point number from a multiple-precision rational
+
+Copyright 2000, 2001, 2002, 2004, 2005, 2006, 2007, 2008, 2009 Free Software Foundation, Inc.
+Contributed by the Arenaire and Cacao 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 2.1 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.LIB.  If not, 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"
+
+/*
+ * Set f to z, choosing the smallest precision for f
+ * so that z = f*(2^BPML)*zs*2^(RetVal)
+ */
+static int
+set_z (mpfr_ptr f, mpz_srcptr z, mp_size_t *zs)
+{
+  mp_limb_t *p;
+  mp_size_t s;
+  int c;
+  mp_prec_t pf;
+
+  MPFR_ASSERTD (mpz_sgn (z) != 0);
+
+  /* Remove useless ending 0 */
+  for (p = PTR (z), s = *zs = ABS (SIZ (z)) ; *p == 0; p++, s--)
+    MPFR_ASSERTD (s >= 0);
+
+  /* Get working precision */
+  count_leading_zeros (c, p[s-1]);
+  pf = s * BITS_PER_MP_LIMB - c;
+  if (pf < MPFR_PREC_MIN)
+    pf = MPFR_PREC_MIN;
+  mpfr_init2 (f, pf);
+
+  /* Copy Mantissa */
+  if (MPFR_LIKELY (c))
+    mpn_lshift (MPFR_MANT (f), p, s, c);
+  else
+    MPN_COPY (MPFR_MANT (f), p, s);
+
+  MPFR_SET_SIGN (f, mpz_sgn (z));
+  MPFR_SET_EXP (f, 0);
+
+  return -c;
+}
+
+/* set f to the rational q */
+int
+mpfr_set_q (mpfr_ptr f, mpq_srcptr q, mp_rnd_t rnd)
+{
+  mpz_srcptr num, den;
+  mpfr_t n, d;
+  int inexact;
+  int cn, cd;
+  long shift;
+  mp_size_t sn, sd;
+  MPFR_SAVE_EXPO_DECL (expo);
+
+  num = mpq_numref (q);
+  den = mpq_denref (q);
+  /* NAN and INF for mpq are not really documented, but could be found */
+  if (MPFR_UNLIKELY (mpz_sgn (num) == 0))
+    {
+      if (MPFR_UNLIKELY (mpz_sgn (den) == 0))
+        {
+          MPFR_SET_NAN (f);
+          MPFR_RET_NAN;
+        }
+      else
+        {
+          MPFR_SET_ZERO (f);
+          MPFR_SET_POS (f);
+          MPFR_RET (0);
+        }
+    }
+  if (MPFR_UNLIKELY (mpz_sgn (den) == 0))
+    {
+      MPFR_SET_INF (f);
+      MPFR_SET_SIGN (f, mpz_sgn (num));
+      MPFR_RET (0);
+    }
+
+  MPFR_SAVE_EXPO_MARK (expo);
+
+  cn = set_z (n, num, &sn);
+  cd = set_z (d, den, &sd);
+
+  sn -= sd;
+  if (MPFR_UNLIKELY (sn > MPFR_EMAX_MAX / BITS_PER_MP_LIMB))
+    {
+      inexact = mpfr_overflow (f, rnd, MPFR_SIGN (f));
+      goto end;
+    }
+  if (MPFR_UNLIKELY (sn < MPFR_EMIN_MIN / BITS_PER_MP_LIMB -1))
+    {
+      if (rnd == GMP_RNDN)
+        rnd = GMP_RNDZ;
+      inexact = mpfr_underflow (f, rnd, MPFR_SIGN (f));
+      goto end;
+    }
+
+  inexact = mpfr_div (f, n, d, rnd);
+  shift = BITS_PER_MP_LIMB*sn+cn-cd;
+  MPFR_ASSERTD (shift == BITS_PER_MP_LIMB*sn+cn-cd);
+  cd = mpfr_mul_2si (f, f, shift, rnd);
+  MPFR_SAVE_EXPO_FREE (expo);
+  if (MPFR_UNLIKELY (cd != 0))
+    inexact = cd;
+  else
+    inexact = mpfr_check_range (f, inexact, rnd);
+ end:
+  mpfr_clear (d);
+  mpfr_clear (n);
+  return inexact;
+}
+
+