[Haskell-beginners] Constructor classes and type classes.

[PATRICK BROWNE]

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
<http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.36.9395> 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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