* mpz/divis.c, mpz/divis_ui.c, mpz/cong.c, mpz/cong_ui.c: Allow d=0,

	under the rule n==c mod d iff exists q satisfying n=c+q*d.

4 files changed, 15 insertions, 17 deletions

diff --git a/mpz/cong.c b/mpz/cong.c
index bfafb98c1..f01595adc 100644
--- a/mpz/cong.c
+++ b/mpz/cong.c
@@ -60,8 +60,9 @@ mpz_congruent_p (mpz_srcptr a, mpz_srcptr c, mpz_srcptr d)
   TMP_DECL (marker);
 
   dsize = SIZ(d);
-  if (dsize == 0)
-    DIVIDE_BY_ZERO;
+  if (UNLIKELY (dsize == 0))
+    return (mpz_cmp (a, c) == 0);
+
   dsize = ABS(dsize);
   dp = PTR(d);
 
diff --git a/mpz/cong_ui.c b/mpz/cong_ui.c
index ddf83faca..05927dc76 100644
--- a/mpz/cong_ui.c
+++ b/mpz/cong_ui.c
@@ -37,8 +37,8 @@ mpz_congruent_ui_p (mpz_srcptr a, unsigned long cu, unsigned long du)
   mp_size_t  asize;
   mp_limb_t  c, d, r;
 
-  if (du == 0)
-    DIVIDE_BY_ZERO;
+  if (UNLIKELY (du == 0))
+    return (mpz_cmp_ui (a, cu) == 0);
 
   asize = SIZ(a);
   if (asize == 0)
diff --git a/mpz/divis.c b/mpz/divis.c
index ca65ea851..8c36c2c60 100644
--- a/mpz/divis.c
+++ b/mpz/divis.c
@@ -1,6 +1,5 @@
-/* mpz_divisible_p -- mpz by mpz divisibility test */
+/* mpz_divisible_p -- mpz by mpz divisibility test
 
-/*
 Copyright 2001, 2002 Free Software Foundation, Inc.
 
 This file is part of the GNU MP Library.
@@ -18,8 +17,7 @@ License for more details.
 You should have received a copy of the GNU Lesser General Public License
 along with the GNU MP 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.
-*/
+MA 02111-1307, USA. */
 
 #include "gmp.h"
 #include "gmp-impl.h"
@@ -27,12 +25,11 @@ MA 02111-1307, USA.
 int
 mpz_divisible_p (mpz_srcptr a, mpz_srcptr d)
 {
-  mp_size_t dsize;
+  mp_size_t dsize = SIZ(d);
+  mp_size_t asize = SIZ(a);
 
-  dsize = SIZ(d);
-  if (dsize == 0)
-    DIVIDE_BY_ZERO;
+  if (UNLIKELY (dsize == 0))
+    return (asize == 0);
 
-  return mpn_divisible_p (PTR(a), (mp_size_t) ABSIZ(a),
-                          PTR(d), (mp_size_t) ABS(dsize));
+  return mpn_divisible_p (PTR(a), ABS(asize), PTR(d), ABS(dsize));
 }
diff --git a/mpz/divis_ui.c b/mpz/divis_ui.c
index 9d053ba87..1d5dc3cb2 100644
--- a/mpz/divis_ui.c
+++ b/mpz/divis_ui.c
@@ -31,10 +31,10 @@ mpz_divisible_ui_p (mpz_srcptr a, unsigned long d)
   mp_ptr     ap;
   unsigned   twos;
 
-  if (d == 0)
-    DIVIDE_BY_ZERO;
-
   asize = SIZ(a);
+  if (UNLIKELY (d == 0))
+    return (asize == 0);
+
   if (asize == 0)  /* 0 divisible by any d */
     return 1;