(let hooks {}
  (def hook-names ()
    (hash-keys hooks))

  (def hooks-for (hook-name)
    hooks.,hook-name)

  (def add-hook (hook-name f)
    (hash-cons hooks hook-name f))

  (def clear-hooks (hook-name)
    (= hooks.,hook-name nil))

  (def remove-hook (hook-name f)
    (= hooks.,hook-name
       (collect (curry !eq? f)
               hooks.,hook-name)))

  (def run-hooks (hook-name . args)
    (each hook (hooks-for hook-name)
          (apply hook args))))