PredicateSet.hs

module Main where
    main = putStrLn (show (fforall (\x -> (x >= -1000)) (setInt)))

    type Set a = a -> Bool

    setInt :: Set Int
    setInt = \x -> True

    --filtering the range with the set function and checking if all elements from the set satisfy the predicate
    fforall :: Restrict a => (a -> Bool) -> Set a -> Bool
    fforall pred set = all pred (filter set range)

    -- Typeclass used to restrict the forall search to a given list of items
    class Restrict a where
        range :: [a]

    instance Restrict Int where
        range = [-1000 .. 1000]