score-assign.clj

(defn score-assign 
  "Log probability of assigning word to tag"
  [state word-info tag]
  (+ ;; Tag Prior
     (log-prob (:tag-prior state)  tag)
     ;; Feature Prob
     (sum
       (fn t1 [[k v]]
         (log-prob (get-in state [:feat-distrs tag k]) v))
       (:feats word-info))
     ;; Token Transition/Emission Prob
     ;; There's a subtely here in that we need to add one to the num-keys
     ;; for the emission distribution
     (let [type-assigns (-> state :type-assigns (assoc (:word word-info) tag))
           word-log-prob
             (-> (:emission-distrs state)
                 (get tag)
                 (update-in [:num-keys] inc)
                 (log-prob (:word word-info)))]           
        (sum
            (fn t2 [[[before after] count]]
              (let [before-tag (type-assigns before) after-tag (type-assigns after)]                    
                (* count
                   (+ word-log-prob
                      (-> state :trans-distrs (get before-tag) (log-prob tag))
                      (-> state :trans-distrs (get tag) (log-prob after-tag))))))
            (-> word-info :contexts :counts)))))