Merge pull request #3 from purescript/docs

Docs pending laws

Author: paf31

README.md

@@ -2,13 +2,28 @@
 
 ## Module Data.Unfoldable
 
+
+This module provides a type class for _unfoldable functors_, i.e.
+functors which support an `unfoldr` operation.
+
+This allows us to unify various operations on arrays, lists,
+sequences, etc.
+
 #### `Unfoldable`
 
 ``` purescript
 class Unfoldable t where
   unfoldr :: forall a b. (b -> Maybe (Tuple a b)) -> b -> t a
 ```
 
+This class identifies data structures which can be _unfolded_,
+generalizing `unfoldr` on arrays.
+
+The generating function `f` in `unfoldr f` in understood as follows:
+
+- If `f b` is `Nothing`, then `unfoldr f b` should be empty.
+- If `f b` is `Just (Tuple a b1)`, then `unfoldr f b` should consist of `a`
+  appended to the result of `unfoldr f b1`.
 
 #### `unfoldableArray`
 

src/Data/Unfoldable.purs

@@ -1,3 +1,9 @@
+-- | This module provides a type class for _unfoldable functors_, i.e.
+-- | functors which support an `unfoldr` operation.
+-- |
+-- | This allows us to unify various operations on arrays, lists,
+-- | sequences, etc.
+
 module Data.Unfoldable where
 
 import Data.Maybe
@@ -6,6 +12,14 @@ import Data.Array.ST
 import Control.Monad.Eff
 import Control.Monad.ST
 
+-- | This class identifies data structures which can be _unfolded_,
+-- | generalizing `unfoldr` on arrays.
+-- |
+-- | The generating function `f` in `unfoldr f` in understood as follows:
+-- |
+-- | - If `f b` is `Nothing`, then `unfoldr f b` should be empty.
+-- | - If `f b` is `Just (Tuple a b1)`, then `unfoldr f b` should consist of `a`
+-- |   appended to the result of `unfoldr f b1`.
 class Unfoldable t where
   unfoldr :: forall a b. (b -> Maybe (Tuple a b)) -> b -> t a