30 lines
990 B
Haskell
30 lines
990 B
Haskell
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import Control.Monad (mapM_)
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import Data.List (nub)
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type Pair = (Integer, Integer)
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type Relation = (Pair, Pair)
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cartesianProduct :: [Integer] -> [Pair]
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cartesianProduct domain = [ (x,y) | x <- domain,
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y <- domain ]
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calculateRelations :: [Pair] -> (Pair -> Pair -> Bool) -> [Relation]
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calculateRelations set relation
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= nub [ (p1, p2) | p1 <- set,
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p2 <- set,
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relation p1 p2 ]
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getRelatedPairsOf :: Pair -> [Relation] -> [Pair]
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getRelatedPairsOf s r = [ p2 | (p1, p2) <- r,
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p1 == s ]
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main :: IO ()
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main = do
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let
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-- set a be the cartesian product of two lists of integers from 1 to and including 5
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setA = cartesianProduct [1..5]
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-- set r be the relation on a that satisfy the following condition
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r = calculateRelations setA (\(x,y) (u,v) -> x+y == u+v)
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-- filter out the equivalence classes of the following pairs
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mapM_ (print . flip getRelatedPairsOf r) [(1,3), (2,4), (1,1)]
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