使用IO与Ncurses的

https://john-millikin.com/software/haskell-ncurses/reference/haskell-ncurses/latest/

对于一些简单的寻路教训的问题是我有一个随机的诠释，当然它返回一个IO诠释然后手段我有一个IO TerrianType然后导致一个IO阵列TerrianType

问题是我需要解决这些在主要，所以他们可以打印到屏幕使用drawString。我包括下面的代码：我想你混淆了[IO TerrianType]和IO [TerrianType]

module Main where 
    2 import UI.NCurses 
    3 import Control.Monad 
    4 import Control.Monad.IO.Class 
    5 import System.Random 
    6 
    7 -- Tutorials 
    8 -- working on several path findng algorithims 
    9 -- http://www.redblobgames.com/pathfinding/a-star/introduction.html 
10 
11 -- | The 'Compass' data type provides breadcrumbs from the goal to the start. 
12 data Compass = N | S | E | W deriving (Show, Eq) 
13 
14 -- | 'Cartogram' is a structure of compass directions that mirrors the terrian. 
15 type Cartogram = [Compass] 
16 
17 -- | 'TerrianType' determines how hard a cell is to traverse. 
18 data TerrianType = Sand | Forest | Goal deriving (Show, Eq) 
19 
20 -- | 'Terrian' is a collection of TerrianTypes with a single goal. 
21 type Terrian = [IO TerrianType] 
22 
23 -- | 'roll' gets a random int from 1 to the parameter 
24 roll :: Int -> IO Int 
25 roll m 
26  | m <= 0 = getStdRandom (randomR (1,1)) 
27  | m > 0 = getStdRandom (randomR (1,m)) 
28 
29 -- | 'getRandomTerrian' gets a random TerrianType 
30 getRandomTerrian :: IO TerrianType 
31 getRandomTerrian = do 
32  r <- roll 3 
33  case r of 
34  1 -> return Forest 
35  2 -> return Sand 
36  3 -> return Goal 
37  _ -> return Sand 
38 
39 -- | 'constructTerrian' constructs a Terrian array of random TerrianTypes 
40 constructTerrian :: Int -> Int -> Terrian 
41 constructTerrian n1 n2 = take (n1 * n2) $ repeat getRandomTerrian 
42 
43 drawShow a = (drawString . show) a 
44 
45 --showString :: t -> String 
46 --showString t = show t 
47 
48 main :: IO() 
49 main = do 
50  runCurses $ do 
51  setEcho False 
52  w <- defaultWindow 
53  updateWindow w $ do 
54   moveCursor 1 1 
55   mapM drawShow (constructTerrian 5 5) 
56  render 
57  waitFor w (\ev -> ev == EventCharacter 'q' || ev == EventCharacter 'Q')58 
59 waitFor :: Window -> (Event -> Bool) -> Curses() 
60 waitFor w p = loop where 
61  loop = do 
62  ev <- getEvent w Nothing 
63  case ev of 
64   Nothing -> loop 
65   Just ev' -> if p ev' then return() else loop 

• No instance for (Show (IO TerrianType)) 
     arising from a use of ‘drawShow’ 
• In the first argument of ‘mapM’, namely ‘drawShow’ 
     In a stmt of a 'do' block: mapM drawShow (constructTerrian 5 5) 
     In the second argument of ‘($)’, namely 
     ‘do { moveCursor 1 1; 
       mapM drawShow (constructTerrian 5 5) }’

来源

2017-05-06 liminal18

。

在您的代码中，您生成了一个[IO TerrianType]，它是IO操作的列表。当你mapM那，你必须运行如果你想访问他们的TerrianType并打印它的行动。

所以，你可能需要像

drawShow :: (IO TerrianType) -> IO() 
drawShow a = a >>= drawString . show

但是，我不知道是否[IO TerrianType]是开始用正确的事情。除了使用

constructTerrian :: Int -> Int -> [IO TerrianType]

，你现在正在做的，你应该移到

constructTerrian :: Int -> Int -> IO [TerrianType]

，并相应地修改代码。第一个代码不计算随机值，但仅返回将滚动随机值的IO操作列表。也许你现在想要滚动它们，并产生一个值列表，正如第二种类型所暗示的那样。

来源

2017-05-06 09:50:23 chi

嘿泰克斯我会给那一枪。不知道我是否可以做IO [TerrianType]，因为IO来自随机Int，但会尝试 – liminal18

是：无法匹配预期类型'IO Terrian' 与实际类型'[IO TerrianType]' •在表达式中：采取（n1 * n2）$重复getRandomTerrian – liminal18

好越来越近谢谢。 – liminal18

使用IO与Ncurses的

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