On 21 February 2010 14:13, Michael Wood <esiot...@gmail.com> wrote:
> That does demonstrate the difference (or a difference), but I don't
> get 3 printlns.

Ouch, I actually posted the wrong version of the function. Here's an
improvement in the context of a REPL interaction:

1. ensure version:

user> (defn funk [r]
        (dosync
         (println (ensure r))
         (Thread/sleep 5000)
         (println (ensure r))))
#'user/funk
user> (def r (ref 1))
#'user/r
user> (.start (Thread. #(funk r)))
1
nil
user> (dosync (ref-set r 5))
1
5

2. deref version:

user> (defn funk [r]
        (dosync
         (println @r)
         (Thread/sleep 5000)
         (println @r)))
#'user/funk
user> (def r (ref 1))
#'user/r
user> (.start (Thread. #(funk r)))
1
nil
user> (dosync (ref-set r 5))
5
5
5

Note how the deref version prints more lines (because it retries the
transaction).

I'm using a newer commit (49a7d6b8e14050a45df5332e768ba6647752215d),
but this shouldn't make any difference.

Sincerely,
Michał

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