2008/7/10 Ron Alford <[EMAIL PROTECTED]>: > Ok, I'm closer, but I'm running into a problem with typeOf and lists, > of all things: > *WouterTest> typeOf (eVar "v" :: TermExpr) > Planning.Wouter.Expr (Planning.Wouter.:+: WouterTest.Const WouterTest.Var) > *WouterTest> typeOf ([eVar "v"] :: [TermExpr]) > *** Exception: Prelude.undefined > > I'm pretty sure this is the culprit for getName: > *WouterTest> getName testNamed > "*** Exception: Prelude.undefined > > Any hints? > > Also, anyone have hints for how to get automatic derivation of Data (Expr f) ? > I don't want to proliferate the last lines: > deriving instance Data (Expr (And :+: Atomic (Expr (Const :+: Var)))) > deriving instance Data (Expr (Const :+: Var)) > >
I screwed up the example code - it typechecks, but it'll fail at runtime. If you say: > Inr x = undefined and then try to pass 'x' off to another function, you're trying to evaluate the "undeifned", which is a runtime error. You'll want something more like: typeOf1 in@(InR f) = [...] where InL f = (InL undefined) `asTypeOf` in This is approaching silliness, but I've tested the code this time around - so it should even work. -Antoine _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
