Split Dodge.Base

src/ListHelp.hs

@@ -4,6 +4,9 @@ module ListHelp
     , insertOver
     , swapIndices
     , (!?)
+    , safeHead
+    , safeUncons
+    , errorHead
     )where
 import Data.List
 
@@ -31,3 +34,15 @@ xs !? n
                                    0 -> Just x
                                    _ -> r (k-1)) (const Nothing) xs n
 {-# INLINABLE (!?) #-}
+
+safeHead :: [a] -> Maybe a
+safeHead (x:_) = Just x
+safeHead _ = Nothing
+
+safeUncons :: [a] -> Maybe (a,[a])
+safeUncons (x:xs) = Just (x,xs)
+safeUncons _ = Nothing
+
+errorHead :: String -> [a] -> a
+errorHead _ (x:_) = x
+errorHead s [] = error s