Hi TP, On 17/05/13 15:32, TP wrote: | [...] | | So I modify my code by removing "deriving Show", and adding the line: | ---------------------------- | instance Show (Person gender) | ---------------------------- | | But now, I obtain: | | $ runghc test_show.hs | GHC stack-space overflow: current limit is 536870912 bytes. | Use the `-K<size>' option to increase it. | | Why (I imagine this is because there is an infinite loop in the construction | of the show function)? Is there any workaround? To use standalone deriving, you need to write
deriving instance Show (Person gender)
and everything will work fine. By writing
instance Show (Person gender)
you are instead giving an instance with no methods, and the default methods in the Show class contain a loop (so that one can define either show or showsPrec). Hope this helps, Adam P.S. You might like to check out the new DataKinds extension, which would allow Male and Female to be data constructors rather than type constructors. -- The University of Strathclyde is a charitable body, registered in Scotland, with registration number SC015263.