Haskell中是否有漂亮的打印（或显示）抽象？ [英] Is there a pretty printing (or showing) abstraction in Haskell?

问题描述

是否没有标准的方式来打印出最终用户消费的价值？ Show 显然更适合于调试的便利性，因为它的使用约定和 read（显示x ）== x 。

例如，至少没有像

$ b这样的简单包$ b

  class（Show a）=> PShow a where 
 pshow :: a  - > String 
 pshow = show 
 
 pprint ::（PShow a）=> a  - > IO（）
 pprint = putStrLn。 pshow 
  

其中实例的功能类似于

 实例PShow MyType其中
 pshow a = someUserFriendlyStringOf a 
  

请注意，我没有要求提供详尽的漂亮的打印和格式化功能（我看到几个包可以做到这一点），只是为了一个简单的抽象，它被广泛使用，允许漂亮的打印。有没有这样的事情？

解决方案

我刚做了一个 Hoogle 搜索 a - > String ，找到 Language.Haskell.Pretty 模块。

模块定义了三个简单函数：

prettyPrintStyleMode :: Pretty a =>样式 - > PPHsMode - > a - >字符串

使用给定样式和模式的漂亮打印。 p>

prettyPrintWithMode :: Pretty a => PPHsMode - > a - > String

使用默认样式和a

prettyPrint ::漂亮a => a - >字符串
使用默认样式漂亮地打印和defaultMode。

整个类型类似于你所要求的更复杂，但也许它有帮助

Is there no standard way to print out values for end-user consumption? Show is clearly more of a debugging convenience than something that would work for this purpose, given the conventions around its use and the constraint that read (show x) == x.

For example, isn't there at least a simple package like

class (Show a) => PShow a where 
    pshow :: a -> String
    pshow = show

pprint :: (PShow a) => a -> IO () 
pprint = putStrLn . pshow

where instances do something like

instance PShow MyType where
    pshow a = someUserFriendlyStringOf a

Note that I'm not asking for something that provides elaborate pretty printing and formatting functionality (I see several packages that do that) just for a simple abstraction that's widely used that allows for pretty printing. Is there something like this?

解决方案

I just did a Hoogle search for a -> String and found the Language.Haskell.Pretty module.

The module defines three simple functions:

prettyPrintStyleMode :: Pretty a => Style -> PPHsMode -> a -> String
pretty-print with a given style and mode.

prettyPrintWithMode :: Pretty a => PPHsMode -> a -> String
pretty-print with the default style and a given mode.

prettyPrint :: Pretty a => a -> String
pretty-print with the default style and defaultMode.

The whole typeclass seems to be a bit more complex than what you have asked for, but maybe it helps

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