Re: [Haskell-cafe] prettyprint with IO
Haskell-src-exts has had a monadic wrapper over HughesPJ for a long time. It is just a Reader (not a transformer) so it can handle user supplied spacing widths, etc. On 13 April 2012 06:02, Warren Harris warrensomeb...@gmail.com wrote: Thanks for the suggestions. No sooner did I send my message than I came to the same conclusion of creating a monadic version of the combinators to simplify the migration. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] prettyprint with IO
I wrote a parsec parser that does symbols lookups during the parsing process (ParsecT String Store IO a). Now I'd like to write a pretty printer that does the reverse. Unfortunately there doesn't appear to be a transformer version of Text.PrettyPrint.HughesPJ. Can anyone suggest a way to do this? Thanks, Warren ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] prettyprint with IO
Hi Warren, On Thu, Apr 12, 2012 at 6:31 PM, Warren Harris warrensomeb...@gmail.com wrote: I wrote a parsec parser that does symbols lookups during the parsing process (ParsecT String Store IO a). Now I'd like to write a pretty printer that does the reverse. Unfortunately there doesn't appear to be a transformer version of Text.PrettyPrint.HughesPJ. Can anyone suggest a way to do this? Thanks, It seems like the opposite would be a function of type 'a - Store - IO Doc'. Maybe a function of type 'a - ReaderT Store IO Doc' could be easier to work with. If you go this route you could write a lifted versions of (), (+), hcat etc. An example: () :: Applicative m = m Doc - m Doc - m Doc I haven't tried any of this, so I'm not sure if you would get any big win over just using the first suggestion (a function of type 'a - Store - IO Doc') and using the stock combinators and threading the store around by hand. But do let me know if something works out. Antoine ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] prettyprint with IO
On Thu, Apr 12, 2012 at 6:22 PM, Antoine Latter aslat...@gmail.com wrote: Hi Warren, On Thu, Apr 12, 2012 at 6:31 PM, Warren Harris warrensomeb...@gmail.com wrote: I wrote a parsec parser that does symbols lookups during the parsing process (ParsecT String Store IO a). Now I'd like to write a pretty printer that does the reverse. Unfortunately there doesn't appear to be a transformer version of Text.PrettyPrint.HughesPJ. Can anyone suggest a way to do this? Thanks, It seems like the opposite would be a function of type 'a - Store - IO Doc'. Maybe a function of type 'a - ReaderT Store IO Doc' could be easier to work with. If you go this route you could write a lifted versions of (), (+), hcat etc. An example: () :: Applicative m = m Doc - m Doc - m Doc On this note, there are various Wadler-Leijin pretty printers variants on hackage, some lifted into a monad so you can do effects, IO, or whatever. E.g. wl-pprint-extras. In my experience though WL gives worse results than H-PJ despite having some more powerful operators. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] prettyprint with IO
Antoine, Thanks for the suggestions. No sooner did I send my message than I came to the same conclusion of creating a monadic version of the combinators to simplify the migration. It actually worked out fairly well -- most of the code ported over to the monadic version unaltered. The only exception is with literal lists used by combinators such as 'sep', e.g. sep [...]. This has to become sep $ sequence [...] in order to convert the argument into the expected monad. I put my code up on github https://github.com/warrenharris/pretty/blob/master/src/Text/PrettyPrint/Reader.hs. If you can take a look, I'd appreciate your suggestions. Warren On Apr 12, 2012, at 6:22 PM, Antoine Latter wrote: Hi Warren, On Thu, Apr 12, 2012 at 6:31 PM, Warren Harris warrensomeb...@gmail.com wrote: I wrote a parsec parser that does symbols lookups during the parsing process (ParsecT String Store IO a). Now I'd like to write a pretty printer that does the reverse. Unfortunately there doesn't appear to be a transformer version of Text.PrettyPrint.HughesPJ. Can anyone suggest a way to do this? Thanks, It seems like the opposite would be a function of type 'a - Store - IO Doc'. Maybe a function of type 'a - ReaderT Store IO Doc' could be easier to work with. If you go this route you could write a lifted versions of (), (+), hcat etc. An example: () :: Applicative m = m Doc - m Doc - m Doc I haven't tried any of this, so I'm not sure if you would get any big win over just using the first suggestion (a function of type 'a - Store - IO Doc') and using the stock combinators and threading the store around by hand. But do let me know if something works out. Antoine ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
