citystate.clj

(ns n01se.citystate)

(defn vitality
  "Vitality of city."
  [city])

(defn owner
  "Owning city. None is returned if no owner exists."
  [city])

(defn freedom
  "Amount of freedom granted to city by owner."
  [city]
  (condp = (owner city)
    city 0.0 ;; TODO
    None 1.0 ;; No owner means maximum freedom.
    (freedom (owner city))))

(defn contacts
  "All influencing cities, including self."
  [city])

(defn peers
  "All influencing cities except the owner."
  [city]
  (disj (contacts city)
        (owner city)))

(defn distance
  "Distance between two cities.
  If city and source are the same, distance is 1.0."
  [city source]
  (condp = source
    city 1.0
    None 1.0
    3.0 ;; TODO))

(defn efficiency-floor
  "Efficiency of city based on distance to owner."
  [city]
  (/ 1.0 (distance city (owner city))))

(defn efficiency
  "Efficiency percentage of city."
  [city]
  (+ (efficiency-floor city)
     (* (1.0 - (efficiency-floor city))
        (freedom city)
        )))

(defn weighted-avg
  "Returns a number between the numbers a and b.
  If factor is 0, returns a; if factor is 1, returns b"
  [factor a b]
  (+ (* factor (- b a)) a))

(defn efficiency-wa
  "Efficiency percentage of city."
  [city]
  (weighted-avg (freedom (owner city))
                (/ 1.0 (distance city (owner city)))
                1.0))

(defn efficiency-let
  "Efficiency percentage of city."
  [city]
  (let [low (/ 1.0 (distance city (owner city)))]
    (+ low (* (freedom (owner city))
              (- 1.0 low)))))

(defn influence
  "Influence on city from source."
  [city source]
  (* (/ (vitality source)
        (distance city source))
     (if (= source (owner city))
       1.0 ;; owners always get full influence
       (freedom city))))

(defn total-influence
  "Influence on city from all contacts."
  [city]
  (apply + (map #(influence city %) (contacts city))))

(defn new-owner
  "new owner of city. It is possible for the new owner be the same
  as the old owner or there be no new owner."
  [city]
  (some (fn [contact]
          (when (> (/ (influence city contact)
                      (total-influence city))
                   0.5)
            city))
        (contacts city)))

(defn new-owner-let
  "new owner of city. It is possible for the new owner be the same
  as the old owner or there be no new owner."
  [city]
  (let [owner-inf [(owner city) (influence city (owner city))]
        peers-inf (map (fn [peer] 
                         [peer (* (freedom (owner city))
                                  (influence city peer))])
                       (peers city))
        total-inf (apply + (last owner-inf) (map last peers-inf))]
    (some (fn [[city inf]]
            (when (> (/ inf total-inf) 0.5)
              city))
          (cons owner-inf
                peers-inf))))