On 20/11/13 19:36, juan.facorro wrote:
The value for all refs whose value you don't actually modify inside a
transaction should be obtained through ensure
<http://clojuredocs.org/clojure_core/clojure.core/ensure>if you want
to make sure :P their value won't be changed by a different
transaction, that way you get a consistent value when the current
transaction is finally committed.
ok this is an interesting and relevant for me comment....let's take a
step back. Assume the same bank from my previous example and consider
the following function:
(defn total!
"Sum all accounts safely with a consistent view even if other
transactions are still running."
[bank]
(dosync
(reduce +'
(map (comp :curr-balance second) *@bank*))))
What would be the implications of changing the bold bit to *(ensure bank) *?
On a slightly different note, is the mega-ref (the entire map in a ref)
approach generally suggested ? I initially had a map-ref with agents
inside (the accounts) but I find it a lot simpler to just have the
map-ref...what ref-granularity are people suggesting for the bank example?
Jim
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