haskell - How to use a specific constructor from a datatype while there are multiple possible type constructor -


i have following data types , create instance of sport don't know how call type football data type sport. 

`data football  = football { players       :: players     , stadium       :: stadium  }       data tennis  = tennis { players1      :: players     , stadium1      :: stadium  } data sport = sf  football  | st tennis

when do: 

instance show => show (sport a) show football{..} = "<== football ==>" show tennis{..} = "<== tennis ==>"

i error message: couldn't match expected type ‘sport a’ actual type ‘football t6’ tryed other ways , check other example figure out how it... 1 have idea?

thanks in advance :)

you need parentheses here

data sport = sf (football a) | st (tennis a)

then need pattern match against sports, not other types:

instance show => show (sport a)   show (sf football{..}) = "<== football ==>"   show (st tennis{..}) = "<== tennis ==>"

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