Add weak-cache

Question

Makes a weak-cache-factory available. Entries will be eagerly collected by the jvm, rather than only when there's memory pressure.
Implementation is fairly simple. I changed SoftCache to NonStrongCache and added an extra record parameter, which is the function
used to create the reference.
See https://github.com/pnf/core.cache/compare/clojure:master...master

Answer 1

Comment made by: seancorfield

This looks interesting. For backward compatibility reasons, I would not want to change any of the public names, but I'd be open to a patch that is purely additive to add the NonStrongCache and reimplement SoftCache in terms of it, as well as adding the WeakCache.

Answer 2

Reference: https://clojure.atlassian.net/browse/CCACHE-35 (reported by alex+import)