[core libraries] Future of "Text.Show.Functions" module

[Andreas Abel]

Strongly +1 for Show printing valid Haskell.

I'd implement showing for functions as

   data Function = Function

   instance Show (a -> b) where
     show f = "Function"

(I would not assume Haskellers expect a Show-ed function to be Read-able.)

For simple user-friendly display we should add a class to Text.PrettyPrint

   class Pretty a where
     pretty     :: a -> Doc
     pretty     = text . prettyShow

     prettyShow :: a -> String
     prettyShow = render . pretty

This class should become standard for implementing simple pretty 
printing (instead of the abuse of Show).

Cheers,
Andreas


On 19.10.2014 17:36, Brandon Allbery wrote:
> On Sun, Oct 19, 2014 at 8:59 AM, Michael Snoyman <michael at snoyman.com
> <mailto:michael at snoyman.com>> wrote:
>
>     I think this really brings up the question of what `Show` should be
>     used for. If the goal is to be simple serialization with `Read` as
>     the inverse[1], then this is clearly a nonsense instance and
>     shouldn't be included.
>
>
> I think I've said before that it would be nice if we had a specific
> class for debugging displays, given that Read/Show are generally
> oriented toward serialization. Sadly, this would end up requiring a lot
> of repetition, since you couldn't sanely fall back on a default Show
> instance to get a notional Gist (or whatever) instance.



-- 
Andreas Abel  <><      Du bist der geliebte Mensch.

Department of Computer Science and Engineering
Chalmers and Gothenburg University, Sweden

andreas.abel at gu.se
http://www2.tcs.ifi.lmu.de/~abel/