Football rankings

gistfile1.clj

(def m
  [{:home "Manchester United" :away "Manchester City" :home_score 1 :away_score 0}
   {:home "Manchester United" :away "Manchester City" :home_score 2 :away_score 0}
   {:home "Manchester City" :away "Arsenal" :home_score 1 :away_score 1}])
 
(def teams
  {"Manchester United" {:points 1200}
   "Manchester City" {:points 1200}
   "Arsenal" {:points 1200}})

(defn process-match [ts match]
  (let [{:keys [home away home_score away_score]} match]
    (cond
     (> home_score away_score) (update-in ts [home :points] + 3)
     (> away_score home_score) (update-in ts [away :points] + 3)
     (= home_score away_score) (-> ts
                                   (update-in [home :points] + 1)
                                   (update-in [away :points] + 1)))))

> (reduce process-match teams m)
{"Manchester United" {:points 1206}, "Arsenal" {:points 1201}, "Manchester City" {:points 1201}}

The compare function can be used together with case to get less repetition (for the price of less clarity, I guess):

(defn process-match [ts match]
  (let [{:keys [home away home_score away_score]} match]
    (case (compare home_score away_score)
     1 (update-in ts [home :points] + 3)
     -1 (update-in ts [away :points] + 3)
     (-> ts (update-in [home :points] + 1) (update-in [away :points] + 1)))))