Merge pull request #4 from purescript/alternative

Add Alt, Plus, MonadPlus, update Alternative

Author: garyb

README.md

@@ -11,6 +11,8 @@
 
 ### Type Class Instances
 
+    instance altMaybe :: Alt Maybe
+
     instance alternativeMaybe :: Alternative Maybe
 
     instance applicativeMaybe :: Applicative Maybe
@@ -25,8 +27,12 @@
 
     instance monadMaybe :: Monad Maybe
 
+    instance monadPlusMaybe :: MonadPlus Maybe
+
     instance ordMaybe :: (Ord a) => Ord (Maybe a)
 
+    instance plusMaybe :: Plus Maybe
+
     instance showMaybe :: (Show a) => Show (Maybe a)
 
 

bower.json

@@ -16,5 +16,8 @@
     "bower.json",
     "Gruntfile.js",
     "package.json"
-  ]
+  ],
+  "dependencies": {
+    "purescript-control": "~0.2.0"
+  }
 }

src/Data/Maybe.purs

@@ -1,54 +1,65 @@
 module Data.Maybe where
 
-  data Maybe a = Nothing | Just a
-
-  maybe :: forall a b. b -> (a -> b) -> Maybe a -> b
-  maybe b _ Nothing = b
-  maybe _ f (Just a) = f a
-
-  fromMaybe :: forall a. a -> Maybe a -> a
-  fromMaybe a = maybe a (id :: forall a. a -> a)
-
-  isJust :: forall a. Maybe a -> Boolean
-  isJust = maybe false (const true)
-
-  isNothing :: forall a. Maybe a -> Boolean
-  isNothing = maybe true (const false)
-  
-  instance functorMaybe :: Functor Maybe where
-    (<$>) fn (Just x) = Just (fn x)
-    (<$>) _  _        = Nothing
-  
-  instance applyMaybe :: Apply Maybe where
-    (<*>) (Just fn) x = fn <$> x
-    (<*>) Nothing   _ = Nothing
-    
-  instance applicativeMaybe :: Applicative Maybe where
-    pure = Just
-    
-  instance alternativeMaybe :: Alternative Maybe where
-    empty = Nothing
-    (<|>) Nothing r = r
-    (<|>) l       _ = l
-    
-  instance bindMaybe :: Bind Maybe where
-    (>>=) (Just x) k = k x
-    (>>=) Nothing  _ = Nothing
-
-  instance monadMaybe :: Monad Maybe
-
-  instance showMaybe :: (Show a) => Show (Maybe a) where
-    show (Just x) = "Just (" ++ show x ++ ")"
-    show Nothing  = "Nothing"
-
-  instance eqMaybe :: (Eq a) => Eq (Maybe a) where
-    (==) Nothing   Nothing   = true
-    (==) (Just a1) (Just a2) = a1 == a2
-    (==) _         _         = false
-    (/=) a b = not (a == b)
-
-  instance ordMaybe :: (Ord a) => Ord (Maybe a) where
-    compare (Just x) (Just y) = compare x y
-    compare Nothing  Nothing  = EQ
-    compare Nothing  _        = LT
-    compare _        Nothing  = GT
+import Control.Alt
+import Control.Plus
+import Control.Alternative
+import Control.MonadPlus
+
+data Maybe a = Nothing | Just a
+
+maybe :: forall a b. b -> (a -> b) -> Maybe a -> b
+maybe b _ Nothing = b
+maybe _ f (Just a) = f a
+
+fromMaybe :: forall a. a -> Maybe a -> a
+fromMaybe a = maybe a (id :: forall a. a -> a)
+
+isJust :: forall a. Maybe a -> Boolean
+isJust = maybe false (const true)
+
+isNothing :: forall a. Maybe a -> Boolean
+isNothing = maybe true (const false)
+
+instance functorMaybe :: Functor Maybe where
+  (<$>) fn (Just x) = Just (fn x)
+  (<$>) _  _        = Nothing
+
+instance applyMaybe :: Apply Maybe where
+  (<*>) (Just fn) x = fn <$> x
+  (<*>) Nothing   _ = Nothing
+
+instance applicativeMaybe :: Applicative Maybe where
+  pure = Just
+
+instance altMaybe :: Alt Maybe where
+  (<|>) Nothing r = r
+  (<|>) l       _ = l
+
+instance plusMaybe :: Plus Maybe where
+  empty = Nothing
+
+instance alternativeMaybe :: Alternative Maybe
+
+instance bindMaybe :: Bind Maybe where
+  (>>=) (Just x) k = k x
+  (>>=) Nothing  _ = Nothing
+
+instance monadMaybe :: Monad Maybe
+
+instance monadPlusMaybe :: MonadPlus Maybe
+
+instance showMaybe :: (Show a) => Show (Maybe a) where
+  show (Just x) = "Just (" ++ show x ++ ")"
+  show Nothing  = "Nothing"
+
+instance eqMaybe :: (Eq a) => Eq (Maybe a) where
+  (==) Nothing   Nothing   = true
+  (==) (Just a1) (Just a2) = a1 == a2
+  (==) _         _         = false
+  (/=) a b = not (a == b)
+
+instance ordMaybe :: (Ord a) => Ord (Maybe a) where
+  compare (Just x) (Just y) = compare x y
+  compare Nothing  Nothing  = EQ
+  compare Nothing  _        = LT
+  compare _        Nothing  = GT