From: "Shot (Piotr Szotkowski)" <shot@...>
Date: 2008-02-21T04:01:45+09:00
Subject: Re: Object#freeze as a basis for caching of method results?

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Robert Klemme:

> 2008/2/19, Shot (Piotr Szotkowski) <shot@hot.pl>:

>> Is there an idiomatic way to do method-results caching in Ruby?

> http://raa.ruby-lang.org/project/memoize/

Ah, perfect, thanks. From both the gem=E2=80=99s docs and the source itself,
it looks like it nicely handles the caching, provided that either the
memoized method=E2=80=99s result does not depend on the object state or the
object state doesn=E2=80=99t change, right?

> An alternative approach would be to use current state as cache key,
> i.e. create an immutable copy and stuff that along with calculation
> results into a Hash.

Hm, that=E2=80=99s actually an approach worth considering. I do need to take
memory use into account, unfortunately, but it seems this is worth
testing.

I assume this approach highly depends on (a) making sure #freeze freezes
also all referenced objects (like in my original example) and (b) #=3D=3D,
#eql? and #hash are sensibly implemented (because Hash uses them for key
comparison), right?

> I suggest you do not inherit Set. In that case it's easy:
> *you* define which methods change the state of your class.

Hm, that=E2=80=99s true; also, if I get all this right, the ones
that change the state could simply clear Memoize=E2=80=99s cache.

I=E2=80=99ll see how much of the stuff inherited from Set I actually use =
=E2=80=93
quite a bit, I assume, but then I could simply make an instance variable
of @set and pass all these method calls to it (while selectively
invalidating cache)=E2=80=A6

Thanks a *ton*, Robert; as usual, your reply is both
invaluable and makes me think in the right direction.

-- Shot
--=20
  <+aeonite> is there any diet plan that does
             not involve fucking cottage cheese?
<@LordCrank> some of them involve eating it instead

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