group-by

function

since v0.0-927

clojure.core/group-by

Edit

---

Details:

---

See Also:

• partition-by
• frequencies

---

Source docstring:

Returns a map of the elements of coll keyed by the result of
f on each element. The value at each key will be a vector of the
corresponding elements, in the order they appeared in coll.

(defn group-by
  [f coll]
  (persistent!
    (reduce
      (fn [ret x]
        (let [k (f x)]
          (assoc! ret k (conj (get ret k []) x))))
      (transient {}) coll)))

---