http://www.seas.upenn.edu/~cis194/spring13/hw/03-rec-poly.pdf

gistfile1.hs

-- Homework 3 - http://www.seas.upenn.edu/~cis194/spring13/hw/03-rec-poly.pdf

module Golf where

import Data.List

skips :: [a] -> [[a]]
skips xs  = map (\(i,x) -> takeNth i x) $ zipWith (\_ b -> (b, xs)) xs [1..]

takeNth :: Int -> [a] -> [a]
takeNth n xs = [y | (i,y) <- zip [1..] xs, i `mod` n == 0]

localMaxima :: [Integer] -> [Integer]
localMaxima a = [y | (x:y:z:_) <- tails a, x < y && y > z]

writeOneLine :: [Integer] -> String
writeOneLine xs = (map f [0..9]) ++ "\n"
    where f x | elem x xs = '*'
              | otherwise = ' '

writeLines :: [Integer] -> String
writeLines [] = ""
writeLines xs = writeLines (xs \\ uniques) ++ (writeOneLine uniques)
     where uniques = nub xs

histogram :: [Integer] -> String
histogram xs = (writeLines xs) ++ 
               "==========\n"  ++ 
               "0123456789\n"