Summing time durations (given as a string) with Clojure and Joda-Time

sum-time-durations.clj

;; lein try joda-time org.clojure/algo.generic

;; Let's first shave the parsing yak:

(import (org.joda.time.format PeriodFormatterBuilder))

(def h:m-formatter
  (-> (PeriodFormatterBuilder.)
      (.appendHours)
      (.appendSeparator ":")
      (.appendMinutes)
      (.toFormatter)))

(defn parse-h:m [str]
  (-> h:m-formatter
      (.parsePeriod str)
      (.toStandardDuration)))

;; ...and then the addition yak:

(require '[clojure.algo.generic.arithmetic :as g])

(import (org.joda.time Duration))

(defmethod g/+ [Duration Duration] [a b] (.plus a b))

;; ...and now the actual task:

(require '[clojure.string :refer [split]])

(def input (split "4:30 1:35 3:35 1:18" #"\s+"))

(def sum (->> input
              (map parse-h:m)
              (reduce g/+)))