module Exercise_6 where

import Data.List
import Data.Ratio

{-WETT-}

{-
http://zvon.org/other/haskell/Outputlist/find_f.html => Maybe
a) Nothing -> Kein Suchergebnis
b) Just val -> Ergebnis val

n : ... 
Laziness := 
    https://piazza.com/class/k0p7t3553ta63i?cid=247
    https://www.schoolofhaskell.com/school/starting-with-haskell/introduction-to-haskell/6-laziness
-}
traceFractran :: [Rational] -> Integer -> [Integer]
traceFractran fs n = n : res
    where 
        res = case find (\f -> mod n (denominator f) == 0) fs of
            Just val -> traceFractran fs $ round $ val * (n%1)
            Nothing -> []
{-TTEW-}