Haskell：在水平线上移动图像 [英] Haskell: moving image on horizontal line

问题描述

Im对于Haskell来说是新的，并且正在使用表示为类型Img = [String]
我想用一个换行向左或向右移动一行或多行图像。

我已经管理图像向上或向下移动，代码如下：

  moveVer :: Int  - > Img  - > Img 
 moveVer n xs = take len $ drop（mod n len）$ cycle xs 
 where len = length xs 
 
 img 1 = XXXXXX OUTPUT =（moveVer（3）（ img 1））= XX 
 XX XX 
 XX XXXXXX 
 XX XXXXXX 
 XXXXXX XX 
  

现在我正在尝试做同样的事情，但水平移动图像（向左或向右）。
函数定义 moveHor :: Int - > Img - > Img

解决方案

基本算法与垂直移位函数相同，因为 String 也是一个字符列表， [Char] 。

你可以将算法概括为 move 函数，因为 moveVer 的代码实际上只需要一个列表并且不依赖于 Img ：

move :: Int - > [a] - > [a]
move n xs = take len $ drop（mod n len）$ cycle xs
where len = length xs


现在您可以用 move ：来重写您的 moveVer / p>

moveVer :: Int - > Img - > Img
moveVer = move


由于字符串只是一个字符列表，所以可以映射到字符串列表并使用 move 函数来执行水平移动。

  moveHor :: Int  - > Img  - > Img 
 moveHor n = map $ move n 
  

Im new to Haskell and am working with images represented as type Img = [String]. I want to move the image either left or right by 1 or more rows with a wrap.

i've manged to move the images up or down, code below:

moveVer :: Int -> Img -> Img
moveVer n xs = take len $ drop (mod n len) $ cycle xs
      where len = length xs

img 1 = XXXXXX       OUTPUT = (moveVer (3)(img 1))  = XX
          XX                                          XX
          XX                                        XXXXXX  
          XX                                        XXXXXX
        XXXXXX                                        XX

Now i'm trying to do the same thing but move the image horizontally (left or right). function to defined moveHor :: Int -> Img -> Img

解决方案

The fundamental algorithm is the same as your vertical shift function, since String is also a list of characters, [Char].

You can generalize your algorithm to a move function since the code for moveVer really only requires a list and has no dependency on Img:

move :: Int -> [a] -> [a]
move n xs = take len $ drop (mod n len) $ cycle xs
  where len = length xs

Now you can rewrite your moveVer function in terms of move:

moveVer :: Int -> Img -> Img
moveVer = move

And since a string is just a List of characters, you can map over the list of strings and use the move function to do your horizontal movement.

moveHor :: Int -> Img -> Img
moveHor n = map $ move n

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