Underflow semantics changed (not tested).

git-svn-id: svn://scm.gforge.inria.fr/svn/mpfr/trunk@1910 280ebfd0-de03-0410-8827-d642c229c3f4

1 files changed, 8 insertions, 2 deletions

diff --git a/exceptions.c b/exceptions.c
index a8519992f..87341a4b0 100644
--- a/exceptions.c
+++ b/exceptions.c
@@ -167,14 +167,20 @@ mpfr_inexflag_p (void)
 
 #undef mpfr_set_underflow
 
+/* Note: In the rounding to the nearest mode, mpfr_set_underflow
+   always rounds away from 0. In this rounding mode, you must call
+   mpfr_set_underflow with rnd_mode = GMP_RNDZ if the exact result
+   is <= 2^(emin-2) in absolute value. */
+
 int
 mpfr_set_underflow (mpfr_ptr x, mp_rnd_t rnd_mode, int sign)
 {
   int inex;
 
   MPFR_CLEAR_FLAGS(x);
-  if ((rnd_mode == GMP_RNDU && sign > 0)
-   || (rnd_mode == GMP_RNDD && sign < 0))
+  if (rnd_mode == GMP_RNDN
+      || (rnd_mode == GMP_RNDU && sign > 0)
+      || (rnd_mode == GMP_RNDD && sign < 0))
     {
       mp_size_t xn;
       mp_limb_t *xp;