clojure.core/make-hierarchy

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Type: function Added: Clojure 1.0 Examples: 3 Runnable: 0

([])

Creates a hierarchy object for use with derive, isa? etc.

Examples

by shockbob on 2011-08-21 . May have evaluation errors. ▶

;; use make-hierarchy to build your own local hierarchy for derive, isa?, etc. ;; instead of using the global hierarchy ;; note that the first ancestors call returns a nil since that type does not ;; exist in the global hierarchy (def h (make-hierarchy)) #'user/h (def h (derive h ::rect ::shape)) #'user/h (def h (derive h ::square ::rect)) #'user/h h {:parents {:user/square #{:user/rect}, :user/rect #{:user/shape}}, :ancestors {: user/square #{:user/shape :user/rect}, :user/rect #{:user/shape}}, :descendants {:user/rect #{:user/square}, :user/shape #{:user/square :user/rect}}} (ancestors ::square) nil (ancestors h ::square) #{:user/shape :user/rect}

by huahaiy on 2014-12-12 . May have evaluation errors. ▶

; the above hierarchy can be built together with a thread macro: (ns demo.core (:require [clojure.pprint :refer [pprint]])) (defn shapes-hierarchy [] (-> (make-hierarchy) (derive ::rect ::shape) (derive ::square ::rect))) (defn -main [& args] (pprint (shapes-hierarchy))) ;------------------------------------------------------- ; result (Clojure 1.10.2-alpha1 + Java 15) {:parents #:demo.core{:rect #{:demo.core/shape}, :square #{:demo.core/rect}}, :ancestors #:demo.core{:rect #{:demo.core/shape}, :square #{:demo.core/rect :demo.core/shape}}, :descendants #:demo.core{:shape #{:demo.core/rect :demo.core/square}, :rect #{:demo.core/square}}}

by fmnoise on 2018-01-18 . May have evaluation errors. ▶

;; hierarchy can be stored in atom for more flexibility (def service-types (atom (make-hierarchy))) (defn add-local! [service-type] (swap! service-types derive service-type ::local) (defn add-remote! [service-type] (swap! service-types derive service-type ::remote) (defmulti connect :service-type :hierarchy service-types) (defmethod connect ::remote [service] "Connecting to remote service") (defmethod connect ::local [service] "Connecting to local service") (add-remote! ::rest) (add-local! ::com+) (connect {:service-type ::rest}) ;; => "Connecting to remote service" (connect {:service-type ::com+}) ;; => "Connecting to local service"

See also

• clojure.core/isa? (2)
• clojure.core/derive (3)
• clojure.core/underive
• clojure.core/parents (1)
• clojure.core/descendants (1)
• clojure.core/ancestors (1)

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