Hi John, >> > While I'm on the topic, I recently wrote a tool that wanted to >> > traverse deep data structures as produced by haskell-src-exts. ?I >> > wound up with about 50 lines of case expressions and around the time >> > my hands were literally beginning to hurt decided that enough was >> > enough and I should try a generic approach. ?I heard uniplate was >> > pretty easy to use, and was pretty pleased to turn the entire thing >> > into a single line. ?It took me a little longer to figure out I needed >> > to use universeBi since all the examples were monotyped, but once I >> > did it Just Worked. ?Amazing. ?So thanks again! ?And maybe you could >> > mention universeBi in the instant introduction? >> >> Yes, I probably should - I'll try and get to that. Of course, I'd also >> happily accept a patch against >> http://community.haskell.org/~ndm/darcs/uniplate >> >> I use Uniplate inside HLint, and it's invaluable - there are a lot of >> times when List Comp + universeBi really hits the spot. > > Does Uniplate include an instance for: >> instance Uniplate a => Biplate [a] a
No, it only includes: instance Biplate [Char] Char where biplate (x:xs) = plate (:) |* x ||* xs biplate x = plate x I am slightly curious why I didn't include the more general a instead of Char version, but perhaps it doesn't quite work - polymorphic versions of the Direct instances can have problems if you pick weird types. I'll have a think, and if it does always work, I'll include it. Note that if you use the Typeable or Data versions this instance is automatically available. In practice I almost always end up using the Data versions of Uniplate, they require no instance definitions are are good to get started with - you can switch to Direct only if you need the additional performance. Thanks, Neil _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe