A.Enum.frequencies_by

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frequencies_by(enumerable, key_fun)

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Specs

frequencies_by(t(val), (val -> key)) :: %{optional(key) => non_neg_integer()}
when val: value(), key: any()

Returns a map with keys as unique elements given by key_fun and values as the count of every element.

Mirrors Enum.frequencies_by/2 with higher performance for Aja structures.