Merge pull request #33 from sharkdp/fix-oneOf

Include upper boundery in chooseInt, fixes #31

Author: garyb

docs/Test/QuickCheck.md

@@ -21,15 +21,15 @@ main = quickCheck \n -> n + 1 > n
 #### `QC`
 
 ``` purescript
-type QC a = forall eff. Eff (console :: CONSOLE, random :: RANDOM, err :: EXCEPTION | eff) a
+type QC eff a = Eff (console :: CONSOLE, random :: RANDOM, err :: EXCEPTION | eff) a
 ```
 
 A type synonym which represents the effects used by the `quickCheck` function.
 
 #### `quickCheck`
 
 ``` purescript
-quickCheck :: forall prop. (Testable prop) => prop -> QC Unit
+quickCheck :: forall eff prop. (Testable prop) => prop -> QC eff Unit
 ```
 
 Test a property.
@@ -40,7 +40,7 @@ prints the test results to the console.
 #### `quickCheck'`
 
 ``` purescript
-quickCheck' :: forall prop. (Testable prop) => Int -> prop -> QC Unit
+quickCheck' :: forall eff prop. (Testable prop) => Int -> prop -> QC eff Unit
 ```
 
 A variant of the `quickCheck` function which accepts an extra parameter

docs/Test/QuickCheck/Gen.md

@@ -102,7 +102,8 @@ with uniform probability.
 chooseInt :: Int -> Int -> Gen Int
 ```
 
-Create a random generator which chooses an integer from a range.
+Create a random generator which chooses uniformly distributed
+integers from the closed interval `[a, b]`.
 
 #### `oneOf`
 

src/Test/QuickCheck/Gen.purs

@@ -83,14 +83,15 @@ choose a b = (*) (max - min) >>> (+) min <$> uniform where
   min = M.min a b
   max = M.max a b
 
--- | Create a random generator which chooses an integer from a range.
+-- | Create a random generator which chooses uniformly distributed
+-- | integers from the closed interval `[a, b]`.
 chooseInt :: Int -> Int -> Gen Int
 chooseInt a b = clamp <$> lcgStep
   where
   clamp :: Int -> Int
-  clamp x = case x `mod` (b - a) of
+  clamp x = case x `mod` (b - a + one) of
               r | r >= 0 -> a + r
-                | otherwise -> b + r
+                | otherwise -> b + r + one
 
 -- | Create a random generator which selects and executes a random generator from
 -- | a non-empty collection of random generators with uniform probability.