Have you looked at the proposed view patterns? It seems like it would cover the case you gave here. I don't know if there's work being done in this area though.
http://hackage.haskell.org/trac/ghc/wiki/ViewPatterns //Gundberg > Hi, > Lately I have been using pattern guards more than usual and I find > that occasionally I need to nest them (i.e., I have alternatives with > a common prefix). This seems to happen when I need to do some > preliminary checking, followed by some decision making. Here is an > example: > > server text > | Just xs <- parse text > , | "field1" `elem` xs = ... do one thing ... > | "field2" `elem` xs = ... do something else ... > > server _ = ... invalid request ... > > As far as I can see this should be a fairly simple change to the > pattern bindings extension. Would anyone else find this a useful > feature, and if so what syntax should we use? > > -Iavor > _______________________________________________ > Haskell mailing list > Haskell@haskell.org > http://www.haskell.org/mailman/listinfo/haskell > _______________________________________________ Haskell mailing list Haskell@haskell.org http://www.haskell.org/mailman/listinfo/haskell
