Add takeWhile and dropWhile

purescript · Jan 24, 2015 · f527161 · f527161
1 parent 00ff8d2
commit f527161
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diff --git a/README.md b/README.md
@@ -49,6 +49,8 @@
 
     drop :: forall a. Number -> [a] -> [a]
 
+    dropWhile :: forall a. (a -> Boolean) -> [a] -> [a]
+
     elemIndex :: forall a. (Eq a) => a -> [a] -> Number
 
     elemLastIndex :: forall a. (Eq a) => a -> [a] -> Number
@@ -107,6 +109,8 @@
 
     take :: forall a. Number -> [a] -> [a]
 
+    takeWhile :: forall a. (a -> Boolean) -> [a] -> [a]
+
     updateAt :: forall a. Number -> a -> [a] -> [a]
 
     zipWith :: forall a b c. (a -> b -> c) -> [a] -> [b] -> [c]

diff --git a/src/Data/Array.purs b/src/Data/Array.purs
@@ -41,6 +41,8 @@ module Data.Array
   , group'
   , groupBy
   , span
+  , dropWhile
+  , takeWhile
   ) where
 
 import Control.Alt
@@ -354,6 +356,12 @@ span = go []
   go acc p (x:xs) | p x = go (x:acc) p xs
   go acc _ xs           = { init: reverse acc, rest: xs }
 
+takeWhile :: forall a. (a -> Boolean) -> [a] -> [a]
+takeWhile p xs = (span p xs).init
+
+dropWhile :: forall a. (a -> Boolean) -> [a] -> [a]
+dropWhile p xs = (span p xs).rest
+
 instance functorArray :: Functor [] where
   (<$>) = map