On 30 October 2014 11:00, Tobias Florek haskell@ibotty.net http://mailto:haskell@ibotty.net wrote: Quoting Christopher Done (2014-10-29 23:07:54) Well, I think fromList [(1, ‘a’)] is kind of unhelpful: 1. It almost never is a straight copy/paste, you will have to go and add M. to the fromList. Chris Done is hinting at a shortcoming to the usage of Show in the sense of Jeremy Shaw’s ShowExpr: It does not support qualified imports at all. It might be nice to append a My.Module to each function in show‘s output whenever a module is meant to be imported qualified. There might be some heuristics on when that’s the case (hiding parts of Prelude), but that’s certainly something only the compiler (or TH) can do. Technically Data.Typeable has this information:
tyConModule (typeRepTyCon (typeOf (S.fromList [()])))"Data.Set.Base" tyConName (typeRepTyCon (typeOf (S.fromList [()])))"Set" tyConPackage (typeRepTyCon (typeOf (S.fromList [()])))"containers-0.5.5.1"
Data.Generics.Text http://hackage.haskell.org/package/syb-0.3.6/docs/Data-Generics-Text.html can give a more structured output (though it doesn’t), but then there lies the issue:
gshow TruncatedArchive
<interactive>:25:1: No instance for (Data FormatError) arising from a use of ‘gshow’ In the expression: gshow TruncatedArchive In an equation for ‘it’: it = gshow TruncatedArchive Hardly any data types are actually instances of Data. And the ones that are can often be bogus, even “standard” ones like Data.Vector and Data.Text:
gshow (V.fromList [1]) "(*** Exception: toConstr
gshow (T.pack "x") "(*** Exception: Data.Text.Text.toConstr
So while Data.Data could be a perfect solution for printing, at the moment it can’t be relied upon to exist.