Dimitri,

Thanks for taking the time and effort to respond. Your comments have clarified some of my confusion. My motivation is that I am trying to implement the code from a paper with the following data and classes:

{-# LANGUAGE MultiParamTypeClasses #-}

data TimeFacts t = Bef (t, t, TimeFacts t) | New

class SetClass t where

class SetClass t => Time l t where

class Time l t => TimeE l t where

class Time l t => TimeTO l t where

However I cannot get the instances to compile:

instance SetClass (TimeFacts t) where -- OK

instance (SetClass t) => Time TimeFacts t where -- Expecting one more argument to 'TimeFacts'

instance TimeE TimeFacts t where -- Expecting one more argument to 'TimeFacts'

instance TimeTO TimeFacts t where -- Expecting one more argument to 'TimeFacts'

Note, I am only using the headings for the classes and instances, which should be OK.

Any pointers to a solution would be much appreciated.

Regards,

Pat

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