On 19-03-17 02:08:56, Rahul Muttineni wrote: > Syd, can you tell us what kind of things you were trying to print out?
Maybe I wasn't very clear. I'm trying to visualise the internal structure of some of the typechecker's output. I specifically do NOT need to see the output of Outputable's functions. They show the human-readibly version and not the internal structure. Does that answer your question? > Hope that helps, > Rahul > > On Sun, Mar 19, 2017 at 1:14 AM, Edward Z. Yang <[email protected]> wrote: > > > We can't add Show instances for these types because many types > > below them, e.g., Type, are cyclic, and would result in infinite > > output. > > > > Perhaps we can add a new type class which a) faithfully represents > > the Haskell syntax, but b) can deal with cyclic data. I think that's > > something people would like (extra compilation time not withstanding). > > But it sounds annoying to do since the deriving mechanism is not going > > to help you. > > > > Edward > > > > Excerpts from Tom Sydney Kerckhove's message of 2017-03-18 14:03:48 +0100: > > > Dear GHC Devs, > > > > > > I am trying to use GHC as a library but I'm having a lot of trouble with > > > understanding what everything means. > > > Up to now, I have been able to figure out what to do by reading the > > > sources, but it ocured to me that much of my struggles could have been > > > mitigated if the relevant types had Show instances. > > > > > > I am specifically talking about the types concerning type checking. > > > TypecheckedModule and everything below that. > > > I am aware that most of the types have an Outputable instance, but > > > there are two problems with that: > > > > > > - 'Outputting' a value requires DynFlags. (yes, I know about pprTrace) > > > - These instances are not intended to show the internal structure of a > > > value, but rather a 'human readable' representation of a value. > > > > > > My questions for you: > > > > > > - Is there a reason that there are no derived 'Show' instances for most > > > types? > > > - Would you accept a diff that adds these? > > > > > > Thank you for your time. > > > > > _______________________________________________ > > ghc-devs mailing list > > [email protected] > > http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs > > > > > > -- > Rahul Muttineni -- Tom Sydney Kerckhove
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