haskell remove element from list code example

Example 1: delete a as haskell

removeItem _ []                 = []
removeItem x (y:ys) | x == y    = removeItem x ys
                    | otherwise = y : removeItem x ys

Example 2: remove first element list haskell

a = [1, 2, 3, 4]
b = tail a
  
-- b == [2, 3, 4]