Merge pull request #5 from joneshf/master

Added group, groupBy and span.

Author: paf31

README.md

@@ -43,6 +43,12 @@
 
     findLastIndex :: forall a. (a -> Prim.Boolean) -> [a] -> Prim.Number
 
+    group :: forall a. (Eq a) => [a] -> [[a]]
+
+    group' :: forall a. (Ord a) => [a] -> [[a]]
+
+    groupBy :: forall a. (a -> a -> Prim.Boolean) -> [a] -> [[a]]
+
     head :: forall a. [a] -> Maybe a
 
     init :: forall a. [a] -> Maybe [a]
@@ -75,6 +81,8 @@
 
     sortBy :: forall a. (a -> a -> Ordering) -> [a] -> [a]
 
+    span :: forall a. (a -> Prim.Boolean) -> [a] -> { rest :: [a], init :: [a] }
+
     tail :: forall a. [a] -> Maybe [a]
 
     take :: forall a. Prim.Number -> [a] -> [a]

src/Data/Array.purs

@@ -30,6 +30,10 @@ module Data.Array
   , nubBy
   , sort
   , sortBy
+  , group
+  , group'
+  , groupBy
+  , span
   ) where
 
 import Data.Maybe
@@ -283,6 +287,28 @@ foreign import sortJS
   \  };\
   \}" :: forall a. (a -> a -> Number) -> [a] -> [a]
 
+group :: forall a. (Eq a) => [a] -> [[a]]
+group xs = groupBy (==) xs
+
+-- | Performs a sorting first.
+group' :: forall a. (Ord a) => [a] -> [[a]]
+group' = group <<< sort
+
+groupBy :: forall a. (a -> a -> Boolean) -> [a] -> [[a]]
+groupBy = go []
+  where
+  go :: forall a. [[a]] -> (a -> a -> Boolean) -> [a] -> [[a]]
+  go acc _  []     = reverse acc
+  go acc op (x:xs) = let sp = span (op x) xs in
+                     go ((x:sp.init):acc) op sp.rest
+
+span :: forall a. (a -> Boolean) -> [a] -> { init :: [a], rest :: [a] }
+span = go []
+  where
+  go :: forall a. [a] -> (a -> Boolean) -> [a] -> { init :: [a], rest :: [a] }
+  go acc p (x:xs) | p x = go (x:acc) p xs
+  go acc _ xs           = { init: reverse acc, rest: xs }
+
 instance functorArray :: Functor [] where
   (<$>) = map