Clojure

PersistentQueue doesn't implement java.util.List, causing nontransitive equality

Details

  • Type: Defect Defect
  • Status: Open Open
  • Priority: Major Major
  • Resolution: Unresolved
  • Affects Version/s: Release 1.4
  • Fix Version/s: None
  • Component/s: None
  • Labels:
  • Patch:
    Code and Test

Description

PersistentQueue implements Sequential but doesn't implement java.util.List. Lists form an equality partition, as do Sequentials. This means that you can end up with nontransitive equality:

(def q (conj clojure.lang.PersistentQueue/EMPTY 1 2 3))
;=> #user/q
(def al (doto (java.util.ArrayList.) (.add 1) (.add 2) (.add 3)))
;=> #user/al
(def v [1 2 3])
;=> #user/v
(= al v)
;=> true
(= v q)
;=> true
(not= al q)
;=> true

This happens because PersistentQueue is a Sequential but not a List, ArrayList is a List but not a Sequential, and PersistentVector is both.

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Dates

  • Created:
    Updated: