用模式匹配或功能的組合物實施revmap功能

Question

高階函數映射定義：

map :: (a -> b) -> [a] -> [b] 
map f [] = [] 
map f (x:xs) = f x:map f xs 

然後如何編寫與圖形匹配用revmap功能/功能使用組合物？

Answer 1

假設你想要的東西像OCaml中的rev_map功能：

revmap :: (a -> b) -> [a] -> [b] 
revmap f xs = go xs [] 
    where 
    go [] acc  = acc 
    go (x:xs) acc = go xs (f x : acc)