[Haskell-cafe] "desactivate" my Show instance implementations temporarily

[Eric Kow]

On 23 Apr 2012, at 17:49, Evan Laforge wrote:
> I use a custom Pretty class along with HughesPJ, ala ghc's Outputable.
> It means I can omit data or print it out in a more readable form
> (even just rounding floats to %.03f can help a lot), and also get nice
> layout and wrapping.


I think I do something similar, although not hooking it up with a proper pretty printing library (that manages indentation etc), but which just stupid builds strings à  la Show.

http://hackage.haskell.org/packages/archive/GenI/latest/doc/html/NLP-GenI-Pretty.html

I wish I knew about a Commonly Agreed Idiom (or library) for just recursively creating human-friendly text, but I suspect I only say this because I don't have a clear picture what I'm really wishing for.  Does everybody just use HughesPJ?

I'll also mention that it took me a while to untangle all the various notions of showing things in my code.  Now it's

* Show: Haskell
* GraphvizShow: dot
* GeniShow: outputting structures in my custom text format
* Pretty: for talking to humans

Embarrassing to say that until recently my code was a random mismash of uses and unclear thinking.  For example, it hadn't occurred to me that I shouldn't define GeniShow in terms of other things (but vice versa) because I don't want to accidentally change my file format just because I was trying to make something prettier.  Oops.

-- 
Eric Kow <http://erickow.com>

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