Question

我有一个我用Haskell编写的程序，除了IO之外的所有东西都在工作。 IO旨在执行以下操作： - 从用户那里接收一个号码 - 如果此数字为正数，请将多行读入列表，然后获取数字并创建列表并将其传递给将返回输出的函数 - 如果此数字为负数，则仅读取下一行，并取数字和该行并将其传递给返回其他输出的函数

我一直在使用“解释（unlines。地图程序。行）”代码来进行测试，但我不知道如何让它处理多行输入（特别是当行数没有时）常数）

我将不胜感激任何帮助

啊，是的，程序循环

更多细节：程序本身处理四叉树。输入可以是这样的： 8 00000000 00111111 00001111 00001111 00011111 00111100 00111000 在这种情况下，程序会看到8，图片的大小，并构建其相应的四叉树。输出相当复杂，但基本上它将它变成四叉树结构的文本表示。

当前节目：

module Main where

main = interact (unlines . map program . lines) -- the IO here is bologna, as it doesn't do anything with the user input
--turns ones and zeros into easier to distinguish characters
replace 0 = '.'
replace 1 = '*'
program x = display (toArray 8 (t2)) -- just a test case to see if the important functions work, as well as a placeholder for real IO, hopefully
data Quadtree a = Tip | Node a (Quadtree a) (Quadtree a) (Quadtree a) (Quadtree a) -- the quadtree datastructure
leaf x = Node x Tip Tip Tip Tip -- saves some typing
-- this function takes a quadtree and returns a 2-dimensional list of binary digits to draw the picture
toArray a (Node x Tip Tip Tip Tip) = replicate a (replicate a x) 
toArray a (Node x b c d e) = (zipWith (++) (toArray (div a 2) b) (toArray (div a 2) c)) ++ (zipWith (++) (toArray (div a 2) d) (toArray (div a 2) e))
display x = unlines (map (map replace) x) -- gives a printable form of the two dimensional array
-- function that turns a number from base five
basefive x
    | x < 5 = x
    | x >= 5 = basefive (div x 5) * 10 + (mod x 5)
-- inserts into quadtree
insert [] (Node 0 Tip Tip Tip Tip) = Node 1 Tip Tip Tip Tip
insert (x:xs) (Node 0 Tip Tip Tip Tip)
    | x == '1' = Node 2 (insert xs (leaf 0)) (leaf 0) (leaf 0) (leaf 0)
    | x == '2' = Node 2 (leaf 0) (insert xs (leaf 0)) (leaf 0) (leaf 0)
    | x == '3' = Node 2 (leaf 0) (leaf 0) (insert xs (leaf 0)) (leaf 0)
    | x == '4' = Node 2 (leaf 0) (leaf 0) (leaf 0) (insert xs (leaf 0))
insert (x:xs) (Node a b c d e)
    | x == '1' = Node a (insert xs b) c d e
    | x == '2' = Node a b (insert xs c) d e
    | x == '3' = Node a b c (insert xs d) e
    | x == '4' = Node a b c d (insert xs e)
-- builds quadtree from scratch
insertall [] x = x
insertall (x:xs) y = insert x (insertall xs y)
s1 = "9 14 17 22 23 44 63 69 88 94 113" -- the example quadtree "path"; it represents the structure
s2 = ["00000000","00000000","00001111","00001111","00011111","00111111","00111100","00111000"] -- this represents the image
-- function which splits a list in half
split :: [a] -> ([a],[a])
split xs = go xs xs where
  go (x:xs) (_:_:zs) = (x:us,vs) where (us,vs)=go xs zs
  go    xs   _       = ([],xs)
quarter a b c = ((a . split) (map (b . split) c)) -- function which quarters a 2 dimensional list
-- function which takes a 2 dimensional array and returns its tree
toTree a x
    | x == replicate a (replicate a '1') = (leaf 1)
    | x == replicate a (replicate a '0') = (leaf 0)
    | otherwise = Node 2 (toTree (div a 2) (quarter fst fst x)) (toTree (div a 2) (quarter fst snd x)) (toTree (div a 2) (quarter snd fst x)) (toTree (div a 2) (quarter snd snd x))
t2 = toTree 8 s2

s1和s2都是样本用户输入;抛出的随机八个是四叉树图像的大小，它应该也是由用户提供的

Answer 1

所以你真的有一个函数规范：

从用户接收一个数字 - 如果此数字为正数，请将多行读入列表，然后取出数字并创建列表并将其传递给将返回输出的函数 - 如果此数字为负数而不是，只读取下一行，并取数字和该行并将其传递给返回其他输出的函数。

我们可以直接写出这个功能。

interactiveFun f g = do
       let readInt :: String -> Int
           readInt = read
       x <- fmap readInt getLine
       if x > 0
           then print . f . map readInt =<< replicateM x getLine
           else print . g x . readInt =<< getLine

修改：<$>与中缀fmap相同，来自Control.Applicative。它惯用的Haskell，但我为了简单起见我编辑了它。 replicateM来自Control.Monad。您应该导入并使用它 - 许多日常Haskell函数来自Prelude之外的基本库。所有这些基础库都是标准的一部分，可移植，有用，应该大量使用。

Haskell的输入和输出？

1 个答案: