[project @ 2002-07-04 16:22:02 by simonmar]

[ghc-base.git] / GHC / Real.lhs

diff --git a/GHC/Real.lhs b/GHC/Real.lhs
index 13be142..c2e73c0 100644 (file)
--- a/GHC/Real.lhs
+++ b/GHC/Real.lhs
@@ -40,7 +40,18 @@ default ()           -- Double isn't available yet,
 
 \begin{code}
 data  (Integral a)     => Ratio a = !a :% !a  deriving (Eq)
+
+-- | Arbitrary-precision rational numbers, represented as a ratio of
+-- two 'Integer' values.  A rational number may be constructed using
+-- the '%' operator.
 type  Rational         =  Ratio Integer
+
+infinity, notANumber :: Rational
+infinity   = 1 :% 0
+notANumber = 0 :% 0
+
+-- Use :%, not % for Inf/NaN; the latter would 
+-- immediately lead to a runtime error, because it normalises. 
 \end{code}