[Haskell-cafe] Monadic parser vs. combinator parser

[Doaitse Swierstra]

On Jan 31, 2013, at 10:47 , Jan Stolarek <jan.stolarek at p.lodz.pl> wrote:

> Thanks for replies guys. I indeed didn't notice that there are monads and applicatives used in 
> this parser. My thought that monadic parsers are more verbose came from Hutton's paper where the 
> code is definitely less readable than in example I provided.
> 
> There is one more thing that bothers me. It is easy to write a parser that returns Nothing when 
> parsing fails. But I can't figure out a way to add meaningful error messages so that the user 
> knows where did the parsing fail. I experimented with using Either so that I can use Left to pass 
> error messages but this turned out to be inflexible and clutered the code. I will be greatful for 
> any ideas.

Use the uu-parsinglib library, which provides error messages, repairs your errors and using its idioms definition you can even write:

inParens c = iI '(' c ')' Ii

I think you cannot get it shorter and with more functionality.

 Doaitse


> Janek
> 
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