module Lib
    ( isCongruent,
      filterByPredicate
    ) where

isCongruent :: Int -> Int -> Int -> Bool
isCongruent a b d = a `mod` d + 1 == b `mod` d


filterByPredicate :: (a -> Bool) -> [a] -> [a]
filterByPredicate _ [] = []
filterByPredicate predicate (x:xs) 
    | predicate x = x : filteredTail
    | otherwise = filteredTail
    where
        filteredTail = filterByPredicate predicate xs