mapreduce.elm

-- Goal: In point-free style
mapReduce : (a -> b) -> (List b -> c) -> List a -> c

-- Simple
mapReduce mapper reducer list 
  = reducer (List.map mapper list) 
  
-- Remove the last argument via composition
mapReduce mapper reducer 
  = reducer << List.map mapper
  
-- Flip direction of composition
mapReduce mapper reducer = 
  List.map mapper >> reducer 
  
-- Make composition operator into a function
mapReduce mapper reducer = 
  (>>) (List.map mapper) reducer
  
-- Remove the last argument
mapReduce mapper = 
  (>>) (List.map mapper)
  
-- Use composition to remove the last argument
mapReduce =
  (>>) << List.map