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

Tom Ellis tom-lists-haskell-cafe-2013 at jaguarpaw.co.uk
Wed Apr 13 11:48:15 UTC 2016

On Wed, Apr 13, 2016 at 05:12:32PM +0530, Rustom Mody wrote:
> 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.
> 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.

On the contrary, you are out of sync with current Haskell :)  <$> is in the
latest Prelude.  Still, best practices should mandate that tutorials support
earlier releases of Haskell too, to avoid these types of confusion.

> Also I find no megaparsec on hoogle/hayoo

I recommend the Hoogle provided by Stackage.  It searches more packages by
default, including megaparsec.


(Alternatively, I think there is a magic incantation to make the haskell.org
Hoogle search more packages, but I don't know it).


More information about the Haskell-Cafe mailing list