player.hs

import qualified Data.Map as M

type Name = String
data Action = MadeShot | MissedShot | Rebound deriving (Show, Eq)
data Event = Event Name Action
type Players = M.Map Name (Int, Int, Int)

aggregate :: [Event] -> Players
aggregate = M.fromListWith f . map toPair
  where 
    f (a, b, c) (a', b', c') = (a+a', b+b', c+c')
    toPair (Event name action) = case action of
      MadeShot   -> (name, (1, 0, 0))
      MissedShot -> (name, (0, 1, 0))
      Rebound    -> (name, (0, 0, 1))
      
events = [Event "playera" MadeShot, Event "playera" MadeShot, Event "playerb" Rebound]

{-
> aggregate events
fromList [("playera",(2,0,0)),("playerb",(0,0,1))]
-}