atan2.c: quick-and-dirty fix for atan2(y,1)

tests/tatan.c: fix tests from Christopher [x and y were interchanged]


git-svn-id: svn://scm.gforge.inria.fr/svn/mpfr/trunk@4646 280ebfd0-de03-0410-8827-d642c229c3f4

1 files changed, 6 insertions, 0 deletions

diff --git a/atan2.c b/atan2.c
index cbbf292e7..0f5c9175d 100644
--- a/atan2.c
+++ b/atan2.c
@@ -153,6 +153,12 @@ mpfr_atan2 (mpfr_ptr dest, mpfr_srcptr y, mpfr_srcptr x, mp_rnd_t rnd_mode)
       else
         goto set_zero;
     }
+
+  /* When x=1, atan2(y,x) = atan(y). FIXME: more generally, if x is a power
+     of two, we could call directly atan(y/x) since y/x is exact. */
+  if (mpfr_cmp_ui (x, 1) == 0)
+    return mpfr_atan (dest, y, rnd_mode);
+
   MPFR_SAVE_EXPO_MARK (expo);
 
   /* Set up initial prec */