On 5 Oct 2005, at 21:04, Richard Gaskin wrote:

J. Landman Gay wrote:

Richard Gaskin wrote:

I used the file name form to illustrate another difference between HC and Rev: while you would indeed need to open a stack in HC in order to get stuff out of it, in Rev you can get property values of objects in unopened stacks. When you do that the engine reads the file into memory to access what's being requested; if the stack has been accessed before it'll stay in memory (unless you turn on the stack's destroyStack property), so subsequent accesses will be lightning fast.

Just an addendum: Actually, I've been using this technique on multiple stacks, and found that once accessed, the stack stays open until you explicitly close it regardless of its destroystack settings. I found this out after I accessed data from a ton of external stacks and then discovered them all open later on. I had to specifically close them to remove them from RAM (their destroystack was true, so that did the trick.) If an accessed stack has its destroystack set to false, just closing it won't be enough, the script will have to delete it as well. (I know you already know that, Richard, just mentioning it for completeness.)



Actually I didn't know that. Is that a bug? It rather invalidates the destroyStack property, no?


I think we could debate that one for a month or two. :-)

I suppose the destroyStack is intended to apply when a stack is closed, and therefore has been explicitly opened earlier. Referencing an external stack isn't the same as opening it.

Like Jacque, I've been caught out with stacks in memory when I'd long forgotten about. However, one practical problem for the engine to overcome would be to determine when it should purge the stack. Typically, when I reference an external stack, I'm likely to make a few references to it within a handler. Having to reload the stack for each reference could introduce an overhead. (Perhaps referenced stacks should be purged when any currently running handlers finish.)

Meanwhile, I try to remember to specifically delete each externally referenced stack.

Cheers
Dave
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