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import Data.Ord | |
import Data.List | |
nubSimple :: [Int] -> [Int] | |
nubSimple = map head . group . sort | |
nubStable :: [Int] -> [Int] | |
nubStable = map fst . sortBy (comparing snd). map head . | |
groupBy ((. fst).(==).fst) . sort . flip zip [0..] |
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import Control.Arrow ((&&&)) | |
import Data.String (unlines) | |
import Data.List (unfoldr,foldl') | |
histogram :: [Int] -> String | |
histogram = graph . histo | |
histo :: [Int] -> [Int] | |
histo = foldl' oplus [0,0,0,0,0,0,0,0,0,0] | |
where oplus xs i = zipWith ($) (replicate i id ++ [(1+)] ++ repeat id) xs |
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{- | |
Richard Bird's quick algorithm for generating prime numbers. | |
Note that the usual "one-liner" Haskell definition of the | |
sieve is not an honest implementation of the sieve of Eratosthenes. | |
The following algorithm by Bird is a more faithful implementation | |
that is not asymptotically the best, but practically | |
fast enough. Further more, we can reuse the "union" function. | |
For more info see: Melissa E. O’Neill, The genuine sieve of |
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{- | |
A program searching for solutions of a board puzzle | |
given by a friend. | |
The aim is to fill in a 8 by 8 square using the | |
given 8 pieces. Each piece has a particular shape and | |
can be rotated and flipped. | |
I am not satisfied with this program yet. The program |