[taliesinb]

Yes, Associations use the same basic algorithm as Scala and Clojure's hashmaps, and are indeed persistent.

And b[x] there gives 1 as you would expect.

[davorak]

Do you know when that change was put into place? I have been using Mathematica sense version 5 and my intuition was that `b[x] == 3`. Testing in mathematica 8 which I have on hand confirms this.

[taliesinb]

Mathematica 8 doesn't have associations, so you must be testing symbol assignments.

Write a = <||> before running the above code to test this on associations; associations are persistent, the symbol table is not.