deal with wrapping around

Author: MaximilianAlgehed

src/Constrained/NumOrd.hs

@@ -726,12 +726,12 @@ class HasDivision a where
     Specification a
   divideSpec a ts = fromSimpleRepSpec $ divideSpec (toSimpleRep a) ts
 
-instance {-# OVERLAPPABLE #-} (HasSpec a, Integral a, TypeSpec a ~ NumSpec a) => HasDivision a where
+instance {-# OVERLAPPABLE #-} (HasSpec a, MaybeBounded a, Integral a, TypeSpec a ~ NumSpec a) => HasDivision a where
   doDivide = div
 
   divideSpec 0 _ = TrueSpec
   -- TODO This is all wrong and hence the tests are all wrong
-  divideSpec a (NumSpecInterval ml mu) = typeSpec ts
+  divideSpec a (NumSpecInterval (unionWithMaybe max lowerBound -> ml) (unionWithMaybe min upperBound -> mu)) = typeSpec ts
     where
       ts | a > 0 = NumSpecInterval ml' mu'
          | otherwise = NumSpecInterval mu' ml'
@@ -740,13 +740,13 @@ instance {-# OVERLAPPABLE #-} (HasSpec a, Integral a, TypeSpec a ~ NumSpec a) =>
       adjustLowerBound l =
         let r = l `div` a in
         if r * a < l
-        then r + 1
+        then r + signum a
         else r
 
       adjustUpperBound u =
         let r = u `div` a in
         if r * a > u
-        then r - 1
+        then r - signum a
         else r
 
 instance HasDivision Float where

src/Constrained/Test.hs

@@ -49,6 +49,7 @@ import Prettyprinter
 import Test.QuickCheck hiding (Fun)
 import qualified Test.QuickCheck as QC
 import Data.Word
+import Data.Int
 
 -- | Check that a generator from a given `Specification` is sound, it never
 -- generates a bad value that doesn't satisfy the constraint
@@ -396,8 +397,12 @@ instance QC.Arbitrary TestableFn where
         TestableFn $ AddW @Int
       , TestableFn $ NegateW @Int
       , TestableFn $ MultW @Int
-      , TestableFn $ MultW @Float
+      , TestableFn $ MultW @Integer
+      -- These are representative of the bounded types
       , TestableFn $ MultW @Word8
+      , TestableFn $ MultW @Int8
+      , TestableFn $ MultW @Float
+      , TestableFn $ MultW @Double
       , TestableFn $ SizeOfW @(Map Int Int)
       , -- data BaseW
         TestableFn $ EqualW @Int