[erlang-questions] Is there a way to serialise a running process & resume it later (i.e. continuations)

jm <>
Fri Feb 27 00:51:57 CET 2009



Robert Virding wrote:
>
>     To support e.g. the back-button behaviour in browsers elegantly.
>     See the
>     diverse seaside docs for an example how such a web framework can be
>     used, and for a good explanation of why and what read "Inverting back
>     the inversion of control or, continuations versus page-centric
>     programming (2001)"
>     http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.29.3112
>
>
> Seeing the state of a process is kept explicitly in the arguments of 
> the functions implementing it it is easy to save the state of a 
> process and so step "backwards" when you want to. If you wish you can 
> keep a stack of process states and step backwards and forwards as you 
> wish. If the problem is just this then I still don't see the problem.
>

More explicitly,

 * stored an id as part of the URL call it UrlId
 * store contexts, {UrlId, Cxt}, as part of a list for an acceptable 
history range, say 10 histories per browser.
     ie, [{UrlId, Cxt}, ....]

  for an incoming request:
     extract the id, UrlId
     case proplist:lookup(UrlId, Contexts) of
          none ->
              %% return on error page
              error_page(no_context, ....);
         {UrlId, Cxt} ->
              %% Found state do work
               make_page(Cxt, ....)
     end.
  

Something like that should do what you wish. I've glossed over the finer 
points.

Jeff.



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