Hello,

On Fri, Mar 8, 2013 at 1:39 AM, Simon Peyton-Jones <simonpj@microsoft.com> wrote:

What I would like to see is something like:

HsApp (HsApp (HsApp (HsVar "foldl'") (HsVar "+")) (HsLit 0)) (HsVar "xs")

We could derive ‘Show’ on everything but that would generate a LOT of new code, that would seldom be used. Also ‘Show’ doesn’t pretty-print so the result would be illegible.

I have a package called "pretty-show", which can convert standard `Show` instances into human-readable form, and it can also produce HTML renditions of `Show`-ed data structures. It is very useful for debugging or learning a new code base.

I’m a bit dubious. Maybe a better thing might be to improve the existing pretty-printer so it gave you the cues you are looking for?

Agreed that this is probably a better solution, although having derived `Show` instances would allow one to see exactly what data-structure was produced at some point, which can be helpful when figuring out how some part of GHC works.

-Iavor