clojure.core/ref-min-history

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Type: function Added: Clojure 1.1 Examples: 2 Runnable: 0

([ref] [ref n])

Gets the min-history of a ref, or sets it and returns the ref

Examples

by reborg on 2019-02-17 . May have evaluation errors. ▶

(def r (ref 0)) (ref-min-history r) ;; 0 (ref-min-history r 1) ; setter ;; #object[clojure.lang.Ref 0x1f3f02ee {:status :ready, :val 0}] (ref-min-history r) ; getter ;; 1

by reborg on 2019-02-17 . May have evaluation errors. ▶

;; Setting the min history > 0 ;; prevents read faults and related TX restart. ;; Here T2 changes r after T1 started but haven't deref r yet. (def r (ref 0)) ; min-history is zero (future (dosync (println "-Tx starting-") (Thread/sleep 10000) (println "T1:" @r))) ;; -Tx starting- (future (dosync (println "T2:" (alter r inc)))) ;; T2: 1 ;; -Tx starting- ;; T1: 1 ;; Here T1 has one ref history value available and ;; does not restart. (def r (ref 0)) (ref-min-history r 1) (future (dosync (println "-Tx starting-") (Thread/sleep 10000) (println "T1:" @r))) ;; -Tx starting- (future (dosync (println "T2:" (alter r inc)))) ;; T2: 1 ;; T1: 0

See also

• clojure.core/ref (1)
• clojure.core/ref-max-history
• clojure.core/ref-history-count (0)

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