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clojure

Calculating a SHA for a persistent data structure

Is there a library to calculate some sort of a SHA for persistent data structures?

(sha (pr-str <datastructure>)) does not work because sometimes the order of keys are not the same when printed.

Solution

  • While it isn't a cryptographic function, clojure.core/hash-unordered-coll will give you a consistent hash value as long as the collections have the same contents, and maybe you can leverage on that:

    user=> (hash-unordered-coll (sorted-map :b 2 :a 1))
161871944
user=> (hash-unordered-coll {:b 2, :a 1})
161871944
user=> (hash-unordered-coll [[:b 2] [:a 1]])
161871944

    See https://clojuredocs.org/clojure.core/hash-unordered-coll