Alex Osborne wrote:
> Chick Corea wrote:
>> If I understand correctly, the "(binding ...)" macro specifically
>> applies to
>> "Variables", one of Clojure's STM types, thus has dynamic, thead-local
>> scope. Is that right? In which case, it may hide a lexical binding ?
>
> Yes, I think you are basically correct. Maybe this example will help:
No it won't because I totally messed it up (copy-paste errors). Sorry,
I'm not completely awake yet. What I meant was:
(def x 5) ; thread-global nearly immutable root binding
(binding [x 7] ; creates a thread-local binding for x
(set! x 9) ; changes the thread-local binding
(let [t (Thread. (fn []
(println "x in other thread:" x)
(set! x 25)))]
(.start t)
(.join t))
(println "x in main thread:" x)
(def x 72) ; change root-bindings (don't do this!)
(println "x in main thread after 2nd def:" x))
(println "x outside binding:" x)
Output:
x in other thread: 5
Exception in thread "Thread-188" java.lang.RuntimeException:
java.lang.IllegalStateException: Can't change/establish root binding of:
x with set
x in main thread: 9
x in main thread after 2nd def: 9
x in outside binding: 72
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