+{-
+We'd like to have more rules, but for example:
+
+This gives wrong answer (0) for NaN - NaN (should be NaN):
+ "minusDouble x x" forall x#. (-##) x# x# = 0.0##
+
+This gives wrong answer (0) for 0 * NaN (should be NaN):
+ "timesDouble 0.0 x" forall x#. (*##) 0.0## x# = 0.0##
+
+This gives wrong answer (0) for NaN * 0 (should be NaN):
+ "timesDouble x 0.0" forall x#. (*##) x# 0.0## = 0.0##
+
+These are tested by num014.
+-}
+