Move toward indexed external placements

2021-11-15 19:36:31 +00:00
parent 59dc24aff6
commit a7f2b5f3ea
9 changed files with 63 additions and 32 deletions
@@ -6,6 +6,7 @@ module Padding
    , midPadL
    , rotU
    , rotD
+    , rotListAt
    )
    where
 leftPad :: Int -> a -> [a] -> [a]
@@ -37,3 +38,11 @@ rotD :: [a] -> [a]
 {-# INLINE rotD #-}
 rotD [] = []
 rotD xs = last xs : init xs
+
+rotListAt :: Eq a => a -> [a] -> [a]
+rotListAt x' xs = f x' xs []
+  where
+    f x (y:ys) zs
+        | y == x    = y:ys ++ zs
+        | otherwise = f x ys (y:zs)
+    f _ [] zs = zs