{- |

Module : $Header$

Description : Utils extending Data.List and Data.Set

Copyright : (c) Immanuel Normann, Uni Bremen 2007

License : GPLv2 or higher, see LICENSE.txt

Maintainer : inormann@jacobs-university.de

Stability : provisional

Portability : portable

-}

module Search.Data.ListSet where

import qualified Data.List as L

import qualified Data.Set as S

completeCols :: (Ord b) => [[(a,b)]] -> S.Set b

completeCols matrix = intersections (map sndsOf matrix)

where sndsOf row = S.fromList (map snd row)

intersections :: (Ord a) => [S.Set a] -> S.Set a

intersections [] = S.empty

intersections family = foldl1 S.intersection family

s1 = S.fromList [1,2,3]

s2 = S.fromList [2,3,4]

s3 = S.fromList [3,4,5]

s4 = S.fromList [4,5,6]

s = [s1,s2,s3,s4]

{-

*Data.ListSet> intersections [s1,s2]

fromList [2,3]

*Data.ListSet> intersections [s1,s2,s3]

fromList [3]

*Data.ListSet> intersections [s1,s2,s4]

fromList []

-}