Removes a parent/child relationship between parent and
tag. h must be a hierarchy obtained from make-hierarchy, if not
supplied defaults to, and modifies, the global hierarchy.
;; create a simple hierarchy using the global hierarchy
;; and demonstrate how underive is used
user=> (derive ::dog ::animal)
nil
user=> (derive ::spaniel ::dog)
nil
user=> (derive ::tabby ::dog)
nil
user=> (ancestors ::tabby)
#{:user/dog :user/animal}
user=> (underive ::tabby ::dog)
nil
user=> (ancestors ::tabby)
nil
user=>
Source
clojure/core.clj:4967
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(defn underive
"Removes a parent/child relationship between parent and
tag. h must be a hierarchy obtained from make-hierarchy, if not
supplied defaults to, and modifies, the global hierarchy."
{:added "1.0"}
([tag parent] (alter-var-root #'global-hierarchy underive tag parent) nil)
([h tag parent]
(let [parentMap (:parents h)
childsParents (if (parentMap tag)
(disj (parentMap tag) parent) #{})
newParents (if (not-empty childsParents)
(assoc parentMap tag childsParents)
(dissoc parentMap tag))
deriv-seq (flatten (map #(cons (key %) (interpose (key %) (val %)))
(seq newParents)))]
(if (contains? (parentMap tag) parent)
(reduce1 #(apply derive %1 %2) (make-hierarchy)
(partition 2 deriv-seq))
h))))
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