[erlang-questions] Elevator demo

Joe Armstrong <>
Tue Jan 1 12:41:32 CET 2013


On Tue, Jan 1, 2013 at 12:39 AM, Loïc Hoguin <> wrote:

> Hello 2013,
>
> Just a quick link targeted mostly to people who teach Erlang or those who
> want to demonstrate its features.
>
> Last September Scott gave me the code he had for an old Ericsson elevator
> training application that shows an application with a bug, and an upgrade
> available to perform a release upgrade to fix the bug live. As these are
> elevators, the bug (doors opening at every floor) can be quickly seen fixed
> since the elevators will continue moving until their destination without
> the bug triggering anymore once you did the upgrade.
>
>
Cool - this would be a nice example to run in a web browser, just a bit of
websocket magic javascript and svg.


I think (incidentally) that the problem should be posed as a protocol
problem.
ie it is the students job to create a process that implements a "lift
controller"
this is sent messages like

     {floor, 5, pressed, up}
     {lift, 3, pressed, 5}
     ...

(meaning the up button was press on floor 5, the 5 button was pressed inside
lift 3)

and should respond by sending messages like

   {lift,3,go,up}
    ...

etc.

This would make a very nice teaching/learning example - ...


I shall do this if I get time.

/Joe




> You can find the source here:
>
>   https://github.com/extend/**elevators<https://github.com/extend/elevators>
>
> It should work for R15. Probably does for R14 too, but I didn't test it.
>
> As this is an old demo it uses gs, but I will port the code to wx for R16
> once it is released if nobody did it before.
>
> Patches are welcome. Also if you know more about the history behind this
> application, I'm interested and will put these infos in the README file.
>
> --
> Loïc Hoguin
> Erlang Cowboy
> Nine Nines
> http://ninenines.eu
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> 
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