derive

function

since v0.0-927

clojure.core/derive

Edit

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See Also:

• ancestors
• descendants
• isa?
• make-hierarchy

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Source docstring:

Establishes a parent/child relationship between parent and
tag. Parent must be a namespace-qualified symbol or keyword and
child can be either a namespace-qualified symbol or keyword or a
class. h must be a hierarchy obtained from make-hierarchy, if not
supplied defaults to, and modifies, the global hierarchy.

(defn derive
  ([tag parent]
   (assert (namespace parent))
   ;; (assert (or (class? tag) (and (instance? cljs.core.Named tag) (namespace tag))))
   (swap-global-hierarchy! derive tag parent) nil)
  ([h tag parent]
   (assert (not= tag parent))
   ;; (assert (or (class? tag) (instance? clojure.lang.Named tag)))
   ;; (assert (instance? clojure.lang.INamed tag))
   ;; (assert (instance? clojure.lang.INamed parent))
   (let [tp (:parents h)
         td (:descendants h)
         ta (:ancestors h)
         tf (fn [m source sources target targets]
              (reduce (fn [ret k]
                        (assoc ret k
                               (reduce conj (get targets k #{}) (cons target (targets target)))))
                      m (cons source (sources source))))]
     (or
      (when-not (contains? (tp tag) parent)
        (when (contains? (ta tag) parent)
          (throw (js/Error. (str tag "already has" parent "as ancestor"))))
        (when (contains? (ta parent) tag)
          (throw (js/Error. (str "Cyclic derivation:" parent "has" tag "as ancestor"))))
        {:parents (assoc (:parents h) tag (conj (get tp tag #{}) parent))
         :ancestors (tf (:ancestors h) tag td parent ta)
         :descendants (tf (:descendants h) parent ta tag td)})
      h))))

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