It's also doable with just swap!, fwiw:
(defn make-blah [xs]
(let [a (atom [nil xs])]
(fn []
(first (swap! a
(fn [[_ tail]]
[(first tail) (next tail)]))))))
Dave
On Thu, Dec 5, 2013 at 12:43 PM, Mark Engelberg <[email protected]>wrote:
> Although I think that a ref is the right tool for this purpose, for the
> sake of completeness, I'll illustrate the threadsafe way to use an atom
> here:
>
> (defn make-blah [v]
> (let [a (atom v)]
> (fn [] (let [current-val @a]
> (if (compare-and-set! a current-val (rest current-val))
> (first current-val)
> (recur))))))
>
>
>
>
>
> On Thu, Dec 5, 2013 at 12:35 PM, Mark Engelberg
> <[email protected]>wrote:
>
>> It's worth pointing out that if you really care about using it across
>> multiple threads, an atom really isn't the right tool for the job. You
>> should use a ref in order to place both the first and the rest into a
>> single transaction:
>>
>> (defn make-blah [v]
>> (let [a (ref v)]
>> (fn [] (dosync (let [x (first @a)] (alter a rest) x)))))
>>
>>
>>
>> On Thu, Dec 5, 2013 at 12:24 PM, David Simmons
>> <[email protected]>wrote:
>>
>>> Hi Puzzler
>>>>
>>>
>>> I like the first approach you defined and it works perfectly thank you.
>>>
>>> cheers
>>>
>>> Dave
>>>
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