Hi, I'd like to propose an extremely simple extension to ghc's record disambiguation rules,
I wonder if John is teasing us? Nothing wrt to records is simple (IMHO). John seems to be unaware of the threads on 'Records in Haskell' (ghc-users) or 'Type-Directed Name Resolution' (cafe) that have been storming for the last few months. He refers to a web page ...
ideally it would be combined with the 'update' and 'label-based pattern-matching' extensions from this page http://hackage.haskell.org/trac/haskell-prime/wiki/ExistingRecords
... which is several years old, requesting features that have been largely delivered in ghc's -XDIsambiguateRecordFields, -XNamedFieldPuns, and -XRecordWildCards.
my motivation is that I often have record types with multiple constructors but common fields.
Perhaps this is a different requirement to those threads above? Most are dealing with the namespacing problem of common fields in different record types. I think John means common fields under different constructors within the same type(?).
so, my proposal is that when you come across something like
(e::RecType) { blah = foo }
(with an explicit type signature like shown)
It's certainly an innovation to go looking for an explicit type sig. within an expression. Does anything else in Haskell do that?
It ... would be a new thing for patterns which generally don't allow type signatures there.
It sidesteps type checker interactions by only being triggered when an explicit type annotation is included.
John
"Extremely simple"? I don't think so. I've added a suggested approach to approximate what John is asking for to my DORF proposal. http://hackage.haskell.org/trac/ghc/wiki/Records/DeclaredOverloadedRecordFie... -- as a **speculative** **future** development. The ease with which I could do that (both a polymorphic record update _and_ polymorphic record pattern match) suggests my proposal is powerful enough to achieve the limited aims for the namespacing issue, with some headroom. -- But then I would say that, wouldn't I! (By the way, none of the 'Records in Haskell' proposals describe themselves as "extremely simple". http://hackage.haskell.org/trac/ghc/wiki/Records AntC -- View this message in context: http://haskell.1045720.n5.nabble.com/simple-extension-to-ghc-s-record-disamb... Sent from the Haskell - Glasgow-haskell-users mailing list archive at Nabble.com.