<aside> This is almost a reprise of a question that came up back in July [1]. At the time, Mark Jones posted a reference [2], but I'm not seeing how it is relevant to this issue of case expressions. [1] http://haskell.org/pipermail/haskell-cafe/2003-July/004708.html [2] ftp://ftp.research.bell-labs.com/dist/smlnj/papers/92-tr-aitken.ps </aside> The following code works, but it seems a bit clumsy: [[ mapXsdBoolean = DatatypeMap { -- mapL2V :: String -> Maybe Bool mapL2V = \s -> case s of s | matchT s -> Just True | matchF s -> Just False | otherwise -> Nothing -- mapV2L :: Bool -> Maybe String , mapV2L = Just . (\b -> if b then "true" else "false") } ]] The case expression seems rather an unwieldy way of getting guards into an expression. If this was an ordinary variable declaration rather than a field definition, I'd use a function definition with guards, but I can't see how to make that work with a lambda expression. Is there a neater way? And a supplementary question... do the prelude or standard libraries define any function like this: cond :: Bool -> a -> a -> a cond True a _ = a cond False _ b = b #g ------------ Graham Klyne For email: http://www.ninebynine.org/#Contact