什么是等待并检测Haskell中的按键的简单方法？ [英] What is a simple way to wait for and then detect keypresses in Haskell?

问题描述

我对Haskell很新，所以我正在寻找一种简单的方法来检测按键，而不是使用 getLine 。

如果有人知道任何图书馆或者一些伎俩，那就太好了！

如果有更好的地方如果你不想阻止，你可以使用 code> hReady 来检测一个键是否被按下。这对于想要程序运行的游戏很有用，并且在发生游戏时暂停游戏就可以进行按键操作。

这是一个便利功能：

  ifReadyDo :: Handle  - > IO a  - > IO（也许a）
 ifReadyDo hnd x = hReady hnd>> = f 
其中f True = x>> = return。只要
f _ = return Nothing 
  

可以这样使用：

  stdin`ifReadyDo` getChar 
  

返回一个 Maybe 即如果按下了一个键，并且 Nothing code>否则。

I'm pretty new to Haskell, so I'm looking for a simple-ish way to detect keypresses, rather than using getLine.

If anyone knows any libraries, or some trick to doing this, it would be great!

And if there is a better place to ask this, please direct me there, I'd appreciate it.

解决方案

If you don't want blocking you can use hReady to detect whether a key has been pressed yet. This is useful for games where you want the program to run and pick up a key press whenever it has happened without pausing the game.

Here's a convenience function I use for this:

ifReadyDo :: Handle -> IO a -> IO (Maybe a)
ifReadyDo hnd x = hReady hnd >>= f
   where f True = x >>= return . Just
         f _    = return Nothing

Which can be used like this:

stdin `ifReadyDo` getChar

Returning a Maybe that is Just if a key was pressed and Nothing otherwise.

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