On Thu, Dec 3, 2009 at 6:00 PM, Joachim Breitner
But when I uncommented the definition of toFoo and fromfoo, I got:
Demo.hs:11:9: Couldn't match expected type `Foo' against inferred type `Int' In the expression: id In the definition of `toFoo': toFoo = id In the second argument of `openNewtype', namely `[d| nullFoo :: Foo nullFoo = 0 toFoo :: Int -> Foo toFoo = id .... |]'
And just now, after writing half the code, I find out that $( fun [d|...|] ) runs the type checker on the declarations before passing them to fun, which of course kills my whole approach here, as only having the declarations pass through openNewType will make them type check.
Is there any way to pass declarations to a TH function so that their names are resolved, but their type is not checked (or, alternatively, type errors are ignored).
If not, what would be a sane work-around?
You could switch over to using a quasi-quoter. I think there's one on hackage for parsing haskell declarations you might be able to start with: http://hackage.haskell.org/package/haskell-src-meta More on GHC quasi-quotations: http://www.haskell.org/ghc/docs/latest/html/users_guide/template-haskell.htm... Antoine