[Haskell-cafe] prettyprint with IO
warrensomebody at gmail.com
Fri Apr 13 07:02:52 CEST 2012
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.
On Apr 12, 2012, at 6:22 PM, Antoine Latter wrote:
> Hi Warren,
> On Thu, Apr 12, 2012 at 6:31 PM, Warren Harris <warrensomebody at 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.
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