[project @ 2003-09-23 17:33:12 by sof]

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

diff --git a/GHC/Real.lhs b/GHC/Real.lhs
index c2e73c0..edee350 100644 (file)
--- a/GHC/Real.lhs
+++ b/GHC/Real.lhs
@@ -26,6 +26,7 @@ import GHC.Show
 
 infixr 8  ^, ^^
 infixl 7  /, `quot`, `rem`, `div`, `mod`
+infixl 7  %
 
 default ()             -- Double isn't available yet, 
                        -- and we shouldn't be using defaults anyway
@@ -46,6 +47,10 @@ data  (Integral a)   => Ratio a = !a :% !a  deriving (Eq)
 -- the '%' operator.
 type  Rational         =  Ratio Integer
 
+ratioPrec, ratioPrec1 :: Int
+ratioPrec  = 7         -- Precedence of ':%' constructor
+ratioPrec1 = ratioPrec + 1
+
 infinity, notANumber :: Rational
 infinity   = 1 :% 0
 notANumber = 0 :% 0
@@ -149,7 +154,7 @@ numericEnumFromThenTo   :: (Ord a, Fractional a) => a -> a -> a -> [a]
 numericEnumFromThenTo e1 e2 e3 = takeWhile pred (numericEnumFromThen e1 e2)
                                where
                                 mid = (e2 - e1) / 2
-                                pred | e2 > e1   = (<= e3 + mid)
+                                pred | e2 >= e1  = (<= e3 + mid)
                                      | otherwise = (>= e3 + mid)
 \end{code}
 
@@ -167,18 +172,22 @@ instance  Real Int  where
 instance  Integral Int where
     toInteger i = int2Integer i  -- give back a full-blown Integer
 
-    -- Following chks for zero divisor are non-standard (WDP)
-    a `quot` b =  if b /= 0
-                  then a `quotInt` b
-                  else error "Prelude.Integral.quot{Int}: divide by 0"
-    a `rem` b  =  if b /= 0
-                  then a `remInt` b
-                  else error "Prelude.Integral.rem{Int}: divide by 0"
+    a `quot` 0   = divZeroError
+    a `quot` b =  a `quotInt` b
+
+    a `rem` 0   = divZeroError
+    a `rem` b  = a `remInt` b
+
+    a `div` 0   = divZeroError
+    a `div` b   = a `divInt` b
 
-    x `div` y = x `divInt` y
-    x `mod` y = x `modInt` y
+    a `mod` 0   = divZeroError
+    a `mod` b   = a `modInt` b
 
+    a `quotRem` 0 = divZeroError
     a `quotRem` b = a `quotRemInt` b
+
+    a `divMod`  0 = divZeroError
     a `divMod`  b = a `divModInt`  b
 \end{code}
 
@@ -196,14 +205,19 @@ instance  Real Integer  where
 instance  Integral Integer where
     toInteger n             = n
 
+    a `quot` 0 = divZeroError
     n `quot` d = n `quotInteger` d
-    n `rem`  d = n `remInteger`  d
 
-    n `div` d  =  q  where (q,_) = divMod n d
-    n `mod` d  =  r  where (_,r) = divMod n d
+    a `rem` 0 = divZeroError
+    n `rem`  d = n `remInteger`  d
 
+    a `divMod` 0 = divZeroError
     a `divMod` b = a `divModInteger` b
+
+    a `quotRem` 0 = divZeroError
     a `quotRem` b = a `quotRemInteger` b
+
+    -- use the defaults for div & mod
 \end{code}
 
 
@@ -246,11 +260,10 @@ instance  (Integral a)    => RealFrac (Ratio a)  where
 
 instance  (Integral a)  => Show (Ratio a)  where
     {-# SPECIALIZE instance Show Rational #-}
-    showsPrec p (x:%y) =  showParen (p > ratio_prec)
-                              (shows x . showString " % " . shows y)
-
-ratio_prec :: Int
-ratio_prec = 7
+    showsPrec p (x:%y) =  showParen (p > ratioPrec) $
+                          showsPrec ratioPrec1 x . 
+                          showString " % " . 
+                          showsPrec ratioPrec1 y
 
 instance  (Integral a) => Enum (Ratio a)  where
     {-# SPECIALIZE instance Enum Rational #-}