-- 4.5.1 基本的なリストの処理 myLength :: [a] -> Int myLength [] = 0 myLength (_:xs) = 1 + myLength xs myNull :: [a] -> Bool myNull [] = True myNull _ = False myHead :: [a] -> a myHead (x:_) = x myHead [] = error "empty list" myTail :: [a]…