Declaratieve Talen/Oplossing haskell nqueens

nqueens::Int->[Int]

nqueens n = let list = [1..n] permlist = perms list in getoklist permlist

getoklist::Int->[Int]

getoklist [] = error "geen oplossing" getoklist (x:xs) | listok x = x | otherwise = getoklist xs

listok::[Int]->Bool

listok [] = True listok (a:as) = if (listok2 a as 1) == False then False else listok as

listok2::Int->[Int]->Int->Bool

listok2 _ [] _ = True listok2 a (b:bs) kol | a == (b+kol) = False | a == (b-kol) = False | otherwise = listok2 a bs (kol+1)

--Permuteer de lijst perms :: [k] -> k

perms [] = [[]] perms (x:xs) = concat (map (tussen x) (perms xs)) where

           tussen e [] = e
           tussen e (y:ys) = (e:y:ys) : map (y:) (tussen e ys)

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