Clojure: inc map values

Source: Braveclojure

(reduce (fn [m [k v]] (assoc m k (inc v))) {} {:a 1 :b 2})
{:a 2, :b 3}

NB: In this example, reduce treats the argument {:a 1 :b 2} as a sequence of vectors, like ([:a 1] [:b 2])

or, with reduce-kv

(reduce-kv (fn [m k v] (assoc m k (inc v))) {} {:a 1 :b 2})
{:a 2, :b 3}