On 10.05.2013 14:44, John D. Hume wrote:
> Assume a queue is your only state and `add` and `clear` are your private
> fns that take a queue as first argument.
>
> (defn new-scheduler []
> (let [queue (...)]
> {:add (partial add queue)
> :clear (partial clear queue)}))
>
> There are several disadvantages to this, however. The biggest in my book
> is that it achieves your goal, and you're limited in the same way your
> users are. You can't add behavior to an already created scheduler
> (unless it's built on adding and clearing). Furthermore, if you
> dynamically recompile `add` or `clear`, it won't change the behavior of
> an already created scheduler, since partial has the fns, not the symbols
> or vars that point at them. (These same disadvantages apply to a reified
> protocol.)
You can make dynamic recompilation work by referring to the vars and not
the functions:
{:add (partial #'add queue)
:clear (partial #'clear queue)}
This works because vars implement `IFn` by delegating to the function
they contain.
--
Timo
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