[Fixed bug due to default behaviour of pred and succ (they go via Ints).
Nils Anders Danielsson <nad@cs.chalmers.se>**20050530143214
 Added specific instances.
 Added tests that catch bug.
] {
hunk ./Test/ChasingBottoms/Nat.hs 91
+  succ = (+ 1)
+  pred = subtract 1
hunk ./Test/ChasingBottoms/Nat/Tests.hs 21
+-- The default versions of succ and pred go via Ints, and hence
+-- perform incorrectly in the presence of large natural numbers. Hence
+-- this generator is needed. Other tests can possibly also fail in the
+-- presence of large natural numbers, but QuickCheck does not handle
+-- large numbers very well, especially not when coarbitrary is used,
+-- so we do not use this generator for all tests. Furthermore
+-- defaulting is turned off here and in Test.ChasingBottoms.Nat, and
+-- that should minimise surprises.
+
+largeNat :: Gen Nat
+largeNat = do
+  n <- choose (0, 2 * toInteger (maxBound :: Int))
+  return (fromInteger n)
+
hunk ./Test/ChasingBottoms/Nat/Tests.hs 56
-prop_Nat_Enum_succ (n :: Nat) = succ n == n + 1
-prop_Nat_Enum_pred (n :: Nat) = n > 0 ==> pred n == n - 1
+prop_Nat_Enum_succ =
+  forAll largeNat $ \n ->
+    succ n == n + 1
+prop_Nat_Enum_pred =
+  forAll largeNat $ \n ->
+    n > 0 ==> pred n == n - 1
}