Am Dienstag, 23. März 2004 12:31 schrieben Sie:
Op zo 21-03-2004, om 18:54 schreef Wolfgang Jeltsch:
Hello,
I'm trying to use GHC's deriving mechanism for newtypes in the following way: class C a b instance C [a] Char newtype T = T Char deriving C [a] Unfortunately, this isn't possible. Is there a reason for this? Can I circumvent this restriction?
You can use the deriving mechanism for user-defined class such as the class C above. (see http://www.haskell.org/onlinereport/decls.html#derived-decls)
Since you refer to The Haskell Report, I think that you wanted to say: "You can *not* use the deriving mechanism..." But you *can* use it if you use -fglasgow-exts. I was refering to GHC's extension concerning deriving and newtypes.
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Instead of the deriving construct, you could use the tool DrIFT (http://repetae.net/john/computer/haskell/DrIFT/)
I don't want to have a tool involved.
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Greetings Arjan
Wolfgang