lookup :: Eq a => a -> [(a, b)] -> Maybe b
undefined :: (forall a. a -> a) -> a
  :: (?callStack::CallStack) => (forall a1. a1 -> a1) -> a
lookup ∷ Eq a ⇒ a → [(a, b)] → Maybe b
undefined :: (forall a. a -> a) -> a
  ∷ (?callStack::CallStack) ⇒ (∀ a1. a1 → a1) → a
lookup :: Eq a => a -> [(a, b)] -> Maybe b
undefined :: (forall a. a -> a) -> a
  :: (?callStack::CallStack) => (forall a1. a1 -> a1) -> a