Re: [Haskell-cafe] Trying to reduce memory costs of String duplicates

2009/9/5 Eugene Kirpichov :

Should be easy to implement one. Something like this:

class (Monad m) => MonadIntern e m | e -> m where  intern :: e -> m e

instance (Ord e) => MonadIntern e (State (M.Map e e)) where  intern = modify . insertWith (\old new -> old))

I mean, intern e = (modify . insertWith const $ e) >> (fromJust . (`lookup`e)) `fmap` get. However, that probably also won't compile, but I think you get the idea.

2009/9/5 Günther Schmidt :

...

Hi all,

I'm reading in a data of 216k records into a map of Key, Values Pairs, the values being strings.

As it happens out of 216k String values there really are only about 6.6k distinct string values, so I could save a lot of RAM if I was able to "insert" only actually *new* string values into the map and use references to (string) values that already are in memory instead.

Is there a container that would, if I wanted to insert an element, return a pair of either the previously inserted, equal value and the container unchanged, or the new, previously unknown value and the new container amended by that element?

Günther

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-- Eugene Kirpichov Web IR developer, market.yandex.ru

-- Eugene Kirpichov Web IR developer, market.yandex.ru