-- returns a list where all elements are replaced by the last element
multlast :: [a] -> [a]
multlast [] = []
multlast [a] = [a]
multlast [a,b] = [b,b]
multlast [a,b,c] = [c,c,c]
multlast [a,b,c,d] = [d,d,d,d]