[Haskell-cafe] Finding way around libraries (was parsec reorganization)

[Michael Snoyman]

On Wed, Apr 13, 2016 at 2:42 PM, Rustom Mody <rustompmody at gmail.com> wrote:

> On Wed, Mar 30, 2016 at 10:06 PM, Joe Hillenbrand <joehillen at gmail.com>
> wrote:
>
>> Parsec isn't as maintained as Megaparsec
>> <https://mrkkrp.github.io/megaparsec/>.
>>
>> I recommend checking out the tutorials here
>> <https://mrkkrp.github.io/megaparsec/tutorials.html>.
>>
>
> So under the advice to use megaparsec instead of parsec, I tried the
> examples here:
> https://mrkkrp.github.io/megaparsec/tutorials/fun-with-the-recovery-feature.html
>
> Got a page full of errors starting:
>
> fpl.hs:42:20: Not in scope: ‘<$>’ …
>     Perhaps you meant one of these:
>
> On a hunch I changed
> import Control.Applicative (empty)
> to
> import Control.Applicative
>
> and then it started working.
>

This specific case is most likely due to different versions of GHC being
used. Since 7.10, Prelude exports <$>. To avoid these kinds of problems,
I've started including Stack script interpreter lines at the beginning of
examples to encode exactly which version of GHC and other packages the
example was tested with. In fact, I wrote a blog post about it last week:

http://www.yesodweb.com/blog/2016/04/stackifying-the-cookbook

Michael


> I can only expect that if megaparsec's own official tutorials are thus out
> of sync with current haskell, then parsec's will be even more so.
>
>
> Also I find no megaparsec on hoogle/hayoo
>
> So how does one go about handling the dilemma:
>   - megaparsec : in development but undocumented on hayoo/hoohle
>   - parsec : documented but bitrotten
>
> What/how do haskell pros go about handling such
>
> Thanks
> Rusi
>
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