rapid_check_4_result_tree_helper.hs

buildTree :: Shrink a -> a -> Tree a
buildTree shrinker = build where
  build x = Tree x (map build (shrinker x))

addCounterExample :: (Show a) => a -> Tree Result -> Tree Result
addCounterExample arg = fmap (\r -> overFailure r addToFailure)
  where addToFailure f = f { counterExample = show arg : counterExample f }