From 5dd8d0a8444f6f42bf3115ff4e310208f29af9dd Mon Sep 17 00:00:00 2001
From: Gary Burgess <gary.burgess@gmail.com>
Date: Sat, 4 Apr 2015 23:00:38 +0100
Subject: [PATCH 1/2] Add Arb/CoArb instances for Unit and Ordering

---
 README.md                | 34 +++++++++++++++++++++++++++++++---
 src/Test/QuickCheck.purs | 27 +++++++++++++++++++++++----
 2 files changed, 54 insertions(+), 7 deletions(-)

diff --git a/README.md b/README.md
index 75c7bea..8fe8661 100755
--- a/README.md
+++ b/README.md
@@ -28,11 +28,11 @@ class Arbitrary t where
   arbitrary :: Gen t
 ```
 
-The `Arbitrary` class represents those types whose values can be 
+The `Arbitrary` class represents those types whose values can be
 _randomly-generated_.
 
 `arbitrary` uses the `Gen` monad to express a random generator for
-the type `t`. Combinators in the `Test.QuickCheck.Gen` 
+the type `t`. Combinators in the `Test.QuickCheck.Gen`
 module can be used to construct random generators.
 
 #### `CoArbitrary`
@@ -138,6 +138,34 @@ instance coarbString :: CoArbitrary String
 ```
 
 
+#### `arbUnit`
+
+``` purescript
+instance arbUnit :: Arbitrary Unit
+```
+
+
+#### `coarbUnit`
+
+``` purescript
+instance coarbUnit :: CoArbitrary Unit
+```
+
+
+#### `arbOrdering`
+
+``` purescript
+instance arbOrdering :: Arbitrary Ordering
+```
+
+
+#### `coarbOrdering`
+
+``` purescript
+instance coarbOrdering :: CoArbitrary Ordering
+```
+
+
 #### `AlphaNumString`
 
 ``` purescript
@@ -145,7 +173,7 @@ newtype AlphaNumString
   = AlphaNumString String
 ```
 
-A newtype for `String` whose `Arbitrary` instance generated random 
+A newtype for `String` whose `Arbitrary` instance generated random
 alphanumeric strings.
 
 #### `arbAlphaNumString`
diff --git a/src/Test/QuickCheck.purs b/src/Test/QuickCheck.purs
index ad83f31..0a03bf5 100644
--- a/src/Test/QuickCheck.purs
+++ b/src/Test/QuickCheck.purs
@@ -35,11 +35,11 @@ import qualified Data.String.Unsafe as SU
 
 import Test.QuickCheck.Gen
 
--- | The `Arbitrary` class represents those types whose values can be 
+-- | The `Arbitrary` class represents those types whose values can be
 -- | _randomly-generated_.
--- | 
+-- |
 -- | `arbitrary` uses the `Gen` monad to express a random generator for
--- | the type `t`. Combinators in the `Test.QuickCheck.Gen` 
+-- | the type `t`. Combinators in the `Test.QuickCheck.Gen`
 -- | module can be used to construct random generators.
 class Arbitrary t where
   arbitrary :: Gen t
@@ -100,7 +100,26 @@ instance arbString :: Arbitrary String where
 instance coarbString :: CoArbitrary String where
   coarbitrary s = coarbitrary $ (S.charCodeAt 0 <$> S.split "" s)
 
--- | A newtype for `String` whose `Arbitrary` instance generated random 
+instance arbUnit :: Arbitrary Unit where
+  arbitrary = return unit
+
+instance coarbUnit :: CoArbitrary Unit where
+  coarbitrary _ = perturbGen 1
+
+instance arbOrdering :: Arbitrary Ordering where
+  arbitrary = do
+    n <- (3 *) <$> uniform
+    return $ case n of
+      _ | n < 1 -> LT
+        | n < 2 -> EQ
+        | otherwise -> GT
+
+instance coarbOrdering :: CoArbitrary Ordering where
+  coarbitrary LT = perturbGen 1
+  coarbitrary EQ = perturbGen 2
+  coarbitrary GT = perturbGen 3
+
+-- | A newtype for `String` whose `Arbitrary` instance generated random
 -- | alphanumeric strings.
 newtype AlphaNumString = AlphaNumString String
 

From 4ca4c03d411dab392f253c764b4fe3476efbc4de Mon Sep 17 00:00:00 2001
From: Gary Burgess <gary.burgess@gmail.com>
Date: Sun, 5 Apr 2015 00:36:48 +0100
Subject: [PATCH 2/2] Better Ordering instance

---
 src/Test/QuickCheck.purs | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/Test/QuickCheck.purs b/src/Test/QuickCheck.purs
index 0a03bf5..ba0c5b2 100644
--- a/src/Test/QuickCheck.purs
+++ b/src/Test/QuickCheck.purs
@@ -108,11 +108,11 @@ instance coarbUnit :: CoArbitrary Unit where
 
 instance arbOrdering :: Arbitrary Ordering where
   arbitrary = do
-    n <- (3 *) <$> uniform
+    n <- chooseInt 1 3
     return $ case n of
-      _ | n < 1 -> LT
-        | n < 2 -> EQ
-        | otherwise -> GT
+      1 -> LT
+      2 -> EQ
+      3 -> GT
 
 instance coarbOrdering :: CoArbitrary Ordering where
   coarbitrary LT = perturbGen 1