Re: Mutating existing persistent data

[Lars Ingebrigtsen]

Po Lu <luangruo@yahoo.com> writes:

> Does this really have to be a generalized variable?
>
> Why not use something like `set-persistent-value' and
> `get-persistent-value'?

I think we're moving away from get/set pairs.  We could have gone even
more magical -- reader macros!

Anyway, this is now working, I think, but of course the most difficult
bit, naming, is left to last.  So basically:

(define-sticky-variable foo 'bar)

This defines a sticky wicket foo, I mean object, and `bar' is the
default value if there isn't one already stored.  We access it like
this:

(sticky-value foo)
=> zot

There was apparently a stored value, so we got that back instead of the
initial value.

(setf (sticky-value foo) 'gazonk)
(sticky-value foo)
=> gazonk

These sticky values can be either synchronised or not.  If they're
synchronised, `(sticky-value foo)' will check whether the value has been
updated externally (i.e., from a different Emacs session) and return
that value.  If not, it returns the local value.

(push 'gazonk (sticky-value list-foo))

if `list-foo' is synchronised, will possibly read in the value from the
db first, prepend `gazonk' to it, and then write it back out again.  (So
the other Emacs will get that value next time it accesses (sticky-value
list-foo).

RPC!!!  😱

But we should call this something other than "sticky", because that's
kinda sticky.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no