MA0301/exercise5/scripts/ex8.hs

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2021-03-24 11:48:48 +01:00
import Control.Monad (mapM_)
import Data.List (partition)
-- | Split off any nums that satisfy the relation and return the split and the rest in a tuple
splitOffRelatedNums :: (Integer -> Integer -> Bool) -> [Integer] -> ([Integer],[Integer])
splitOffRelatedNums relation nums = partition (relation x) nums
where
x = head nums
-- | Split off equivalence groups until there are no more that satisfy the condition
getEquivalenceClasses :: (Integer -> Integer -> Bool) -> [Integer] -> [[Integer]]
getEquivalenceClasses relation nums
= case nums of
[] -> []
nums -> x : getEquivalenceClasses relation xs
where
(x,xs) = splitOffRelatedNums relation nums
main :: IO ()
main = do
let
setA = [1..7]
relation :: Integer -> Integer -> Bool
relation x y = (x - y) `mod` 3 == 0
mapM_ print $ getEquivalenceClasses relation setA