Add Lazy

Author: garyb

README.md

@@ -17,9 +17,9 @@
 
 ### Values
 
-    many :: forall f a. (Alternative f) => f a -> f [a]
+    many :: forall f a. (Alternative f, Lazy1 f) => f a -> f [a]
 
-    some :: forall f a. (Alternative f) => f a -> f [a]
+    some :: forall f a. (Alternative f, Lazy1 f) => f a -> f [a]
 
 
 ## Module Control.Apply
@@ -56,6 +56,17 @@
     join :: forall a m. (Bind m) => m (m a) -> m a
 
 
+## Module Control.Lazy
+
+### Type Classes
+
+    class Lazy a where
+      defer :: (Unit -> a) -> a
+
+    class Lazy1 a where
+      defer1 :: forall t. (Unit -> a t) -> a t
+
+
 ## Module Control.Monad
 
 ### Values

src/Control/Alternative.purs

@@ -1,12 +1,14 @@
 module Control.Alternative where
 
 import Control.Alt
+import Control.Lazy
 import Control.Plus
 
 class (Applicative f, Plus f) <= Alternative f
 
-some :: forall f a. (Alternative f) => f a -> f [a]
-some v = (:) <$> v <*> many v
+some :: forall f a. (Alternative f, Lazy1 f) => f a -> f [a]
+some v = (:) <$> v <*> defer1 (\_ -> many v)
 
-many :: forall f a. (Alternative f) => f a -> f [a]
+many :: forall f a. (Alternative f, Lazy1 f) => f a -> f [a]
 many v = some v <|> pure []
+

src/Control/Lazy.purs

@@ -0,0 +1,7 @@
+module Control.Lazy where
+
+class Lazy a where
+  defer :: (Unit -> a) -> a
+
+class Lazy1 a where
+  defer1 :: forall t. (Unit -> a t) -> a t