有没有一种确定的方法来编写可以重建其确切输入的解析器？ [英] Is there an established way to write parsers that can reconstruct their exact input?

问题描述

假设我想用语言 X 解析文件。真的，我只对其中的一小部分信息感兴趣。为了这个目的，在Haskell的许多eDSL之一中编写解析器是很容易的。（例如Megaparsec）。
$ b $ pre $ data $ Foo = Foo Int - 我所追求的信息。

parseFoo :: Parsec Text Foo
parseFoo = ...

<这很容易产生一个函数 getFoo :: Text - >也许Foo 。

但现在我也想修改的来源， Foo 信息，即基本上我想实现

  changeFoo ::（Foo  - > Foo） - >文字 - >文本
  

与属性

  changeFoo id≡id 
 getFoo。 changeFoo f≡fmap f。 getFoo 
  

可以通过将解析器的结果更改为类似镜头的结果来执行此操作

  parseFoo :: Parsec文本（Foo，Foo  - >文本）
 parseFoo = ... 
  

但这会使定义变得更加繁琐–我不能再掩盖不相关的信息，但需要存储每个字符串子匹配的匹配并手动重新组装。

这可以通过将字符串重组保留在解析器monad周围的 StateT 层中来实现某种程度的自动化，但我不能仅仅使用现有的原语解析器。 / p>

是否存在此问题的解决方案？

解决方案

双向转型的情况？例如， http://ceur-ws.org/Vol-1571/

特别是Rendel和Osterman的Invertible Syntax Descriptions：Unifying Parsing和Pretty Printing
http://dblp.org/rec/conf/haskell/RendelO10 ，Haskell Symposium 2010（参见 http://lambda-the-ultimate.org/node/4191 ）

Say I want to parse a file in language X. Really, I'm only interested in a small part of the information within. It's easy enough to write a parser in one of Haskell's many eDSLs for that purpose (e.g. Megaparsec).

data Foo = Foo Int  -- the information I'm after.

parseFoo :: Parsec Text Foo
parseFoo = ...

That readily gives rise to a function getFoo :: Text -> Maybe Foo.

But now I would also like to modify the source of the Foo information, i.e. basically I want to implement

changeFoo :: (Foo -> Foo) -> Text -> Text

with the properties

changeFoo id ≡ id
getFoo . changeFoo f ≡ fmap f . getFoo

It's possible to do that by changing the result of the parser to something like a lens

parseFoo :: Parsec Text (Foo, Foo -> Text)
parseFoo = ...

but that makes the definition a lot more cumbersome – I can't just gloss over irrelevant information anymore, but need to store the match of every string subparse and manually reassemble it.

This could be somewhat automated by keeping the string-reassembage in a StateT layer around the parser monad, but I couldn't just use the existing primitive parsers.

Is there an existing solution for this problem?

解决方案

Is this a case of "bidirectional transformation"? E.g., http://ceur-ws.org/Vol-1571/

In particular, "Invertible Syntax Descriptions: Unifying Parsing and Pretty Printing" by Rendel and Osterman http://dblp.org/rec/conf/haskell/RendelO10 , Haskell Symposium 2010 (cf. http://lambda-the-ultimate.org/node/4191 )

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