[Python-ideas] A Continuations Compromise in Python

[John Graham]

On Mon, May 4, 2009 at 8:11 PM, Greg Ewing <greg.ewing at canterbury.ac.nz> wrote:
> John Graham wrote:
>
>> I believe it would be used for state that is not transferred via the
>> URL, such as a user's session with the server should some sort of
>> persistence take place.
>
> In that case you have a stateful server rather
> than a stateless one.
>
> But I still don't see how the proposed "continue"
> statement would help, because you don't want to
> call the continuation *now*, you want to defer
> it until later. So you still need to store it
> somewhere or return it to a trampoline.
>
> Seems to me a better structure for this would
> be to represent the session by an instance of a
> class, with methods corresponding to the various
> queries that can be sent. Then you've got much
> the same situation as with the stateless server,
> except that the mapping from query string to
> function goes through an intermediates step of
> locating the appropriate session object, based
> on a session id in the query. Still no need
> for continuations anywhere.
>
> --
> Greg
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In this case, continuation-passing-style would force capturing of this
state in the same way many 'functional-style' languages capture state,
immutable state in closures?  I can see how immutable state from
closures might have a benefit when back button and clone-tab buttons
are pressed, since there is no one grand object or class to refer to
per session, but more like little breadcrumbs of immutable state
between function calls.