addElem::Integer -> [(Integer, Integer)] -> [(Integer, Integer)]
addElem a [] = [(a,1)]
addElem a (x:xs) = let (elem, count) = x
                   in if (elem == a)
                      then (elem, count+1):xs
                      else (a, 1):x:xs


countOccurs :: [Integer] -> [(Integer, Integer)]
countOccurs l = foldr addElem [] l