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[REBOL] Lightweight threading / task system impl. questions

From: m::koopmans2::chello::nl at: 1-Feb-2002 10:13

Hi All, In my rewrite o Rugby I am cuurently incorporating a "task" system. It works like a queue of code blocks of which one is executed when there is no IO for a certain time. This may be very useful for others as well, so.... I would like to expose that set in a programmer-friendly way. Normally you'd have interruptable threads with a certain state associated, and you would have to be sure that your IO does not block athread (i.e. prevent it from receiving an interupt). In a functional-style eavluator you'd have to count reductions (and weight them), which is hard with natives.... My current way would be to implement task that executes a certain set of code and hands control back to the Rebol process itself. Something like: task [signature] [ some-code ; suspend; some-other code; suspend; label demo; some-code suspend/on-return demo ] The suspend would put you back in the queue (with state preserved). suspend/on-return with the label will allow for repetetive code blocks in a task. The drawback is obvious: you have to think about how to partition your code in a task. OTOH, you *are* in control. I would typically add a few non-blocking IO operations, such as fetch-web, fetch-file etc. that you could use in your tasks to make sure that IO doesn't hang-up a task. My questions: - Is this workable? - what IO operations should be available at least? - what other blocking operations can you think of? As this is a side effect of Rugby the task system will be there. Depending on the feedback and usefullness it will be visible. --Maarten