convert rational (mpz_q) to floating-point (mpfr_t)

git-svn-id: svn://scm.gforge.inria.fr/svn/mpfr/trunk@474 280ebfd0-de03-0410-8827-d642c229c3f4

1 files changed, 62 insertions, 0 deletions

diff --git a/set_q.c b/set_q.c
new file mode 100644
index 000000000..d56b3bcde
--- /dev/null
+++ b/set_q.c
@@ -0,0 +1,62 @@
+/* mpfr_set_q -- set a floating-point number from a multiple-precision rational
+
+Copyright (C) 2000 PolKA project, Inria Lorraine and Loria
+
+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 "gmp.h"
+#include "gmp-impl.h"
+#include "longlong.h"
+#include "mpfr.h"
+
+/* set f to the rational q */
+void
+#if __STDC__
+mpfr_set_q (mpfr_ptr f, mpq_srcptr q, mp_rnd_t rnd)
+#else
+mpfr_set_q (f, q, rnd) 
+     mpfr_ptr f;
+     mpq_srcptr q;
+     mp_rnd_t rnd;
+#endif
+{
+  int sign;
+  mpz_srcptr num, den;
+  unsigned int prec;
+  mpfr_t n,d;
+
+  num = mpq_numref(q);
+  sign = mpz_cmp_ui(num, 0);
+  if (sign==0) {
+    SET_ZERO(f);
+    return;
+  }
+
+  den = mpq_denref(q);
+  prec = PREC(f);
+  mpfr_init2(n, mpz_sizeinbase(num, 2));
+  mpfr_set_z(n, num, GMP_RNDZ); /* result is exact */
+  mpfr_init2(d, mpz_sizeinbase(den, 2));
+  mpfr_set_z(d, den, GMP_RNDZ); /* result is exact */
+  PREC(f) = prec; 
+  mpfr_div(f, n, d, rnd);
+  mpfr_clear(n); mpfr_clear(d);
+}
+
+
+