improved HashMap.hashCode() implementation inspired by Clojure

emmanueltouzery / prelude-ts

Functional programming, immutable collections and FP constructs for typescript and javascript

ISC License

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Closed fmw closed 1 year ago

fmw commented 1 year ago

There are two important changes:

use bitwise XOR instead of plus operator to combine the hashcode of the key and value, which intertwines them and prevents collisions on hashmaps with values swapped between keys,
cache the hash code internally, to avoid unnecessary recalculations.

I've also added a test that verifies the hashcode doesn't take the order in which the kv-pairs are supplied into account.

fmw commented 1 year ago

(the force push was to fix a typo in the test it description).

emmanueltouzery commented 1 year ago

thanks a lot! i'll try to release this ASAP