Paul Callaghan paulcc

## gist:8142387

      
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              December 27, 2013 03:57
            
              
                Paul Callaghan's FP/DT articles
              
          
http://pragprog.com/magazines/2012-08/thinking-functionally-with-haskell
http://pragprog.com/magazines/2012-09/thinking-functionally-with-haskell
http://pragprog.com/magazines/2012-10/thinking-functionally-with-haskell
http://pragprog.com/magazines/2012-11/thinking-functionally-with-haskell
http://pragprog.com/magazines/2012-12/web-programming-in-haskell
http://pragprog.com/magazines/2013-01/web-programming-in-haskell-part-ii
http://pragprog.com/magazines/2013-03/uncle-bob-and-functional-programming
http://pragprog.com/magazines/2013-04/dependent-types
http://pragprog.com/magazines/2013-05/dependent-types-part-ii
http://pragprog.com/magazines/2013-06/unification


## group_on-full-example.hs
-- compiles with ghc(i) 7.4.1
import Data.Map (Map, empty, insertWith, toList)
import Data.List(groupBy, group, sortBy, sort)

{- To recap from the main article, we want to define "group_on" via "groupBy", so that its
   type is something like (b -> b -> Bool) -> (a -> b) -> [a] -> [(b, [a])]

   The method here is to work with a concrete example and gradually massage it
   into the form we want - using the REPL
	-- compiles with ghc(i) 7.4.1
	import Data.Map (Map, empty, insertWith, toList)
	import Data.List(groupBy, group, sortBy, sort)

	{- To recap from the main article, we want to define "group_on" via "groupBy", so that its
	type is something like (b -> b -> Bool) -> (a -> b) -> [a] -> [(b, [a])]

	The method here is to work with a concrete example and gradually massage it
	into the form we want - using the REPL