Clojure code described in

Frame-language-2.clj

;; this gist contain the CLojure code for the blog post:
;; http://highorderdysfunctions.blogspot.it/2014/03/frame-language-in-clojure-part-2.html
;; Remember to include dependencies for [clj-time "0.6.0"] and [seesaw "1.4.4"] in your project file.

(ns employees.core)
(use 'seesaw.core)
(use 'clj-time.core)
(use 'clj-time.format)
(use 'clojure.test)

;; Knowledge Base

(def employee)

(def unit-coordinator {:ako {:value 'employee}
                       :bonus {:value 5000,00}})
(def accountant       {:ako {:value 'employee}
                       :bonus {:value 3000.00}})

(def Henry {:is-a {:value 'system-analyst} 
            :working-at {:value 'unit-i} 
            :recruitment-date {:value "20100304"} 
            :gross-salary {:value 3000,00}})

(def Bob   {:is-a {:value 'accountant} 
            :working-at {:value 'unit-i} 
            :recruitment-date {:value "20140214"} 
            :years-in-the-role {:value 6}
            :gross-salary {:if-needed 'estimate-salary}})

;; Service functions

(def built-in-formatter (formatters :basic-date-time))
(def basic-formatter (formatter "yyyyMMdd"))

; dissoc-in was once part of clojure.contrib.core, and is now part of core.incubator
(defn dissoc-in
  "Dissociates an entry from a nested associative structure returning a new
  nested structure. keys is a sequence of keys. Any empty maps that result
  will not be present in the new structure."
  [m [k & ks :as keys]]
  (if ks
    (if-let [nextmap (get m k)]
      (let [newmap (dissoc-in nextmap ks)]
        (if (seq newmap)
          (assoc m k newmap)
          (dissoc m k)))
      m)
    (dissoc m k)))

;; Frame Language function

(defn fget
  "Fetches information from a given frame, slot, and facet"
  [frame slot facet]
  (get-in frame [slot facet]))


(defn fput
  "Places information in a given frame, slot, and facet"
  [frame slot facet v]
  (assoc-in frame [slot facet] v))

(defn fput-p
  "Places information in a given frame, slot, and facet and activate the demons :range and :if-added"
  [frame slot facet v]
  (assoc-in frame [slot facet] v)
  (if ((fget frame slot :range) frame slot)
     nil
     ((fget frame slot :if-added) frame slot)))

(defn fremove
  "Remove information in a given frame, slot, and facet"
  [frame slot facet]
  (dissoc-in frame [slot facet]))

(defn fcheck
  "Check if the information stored in a given frame, slot, and facet is equal to value"
  [frame slot facet value]
  (= (fget frame slot facet) value))

(defn fget-v-d
  "Fetches :value information from a given frame and slot or, in case there is no :value facet, fetches :default facet"
  [frame slot]
  (let [v (fget frame slot :value)]
    (if v v (fget frame slot :default))))

(defn fget-v-d-p
  "Fetches :value information from a given frame and slot and, in case there is no :value facet, fetches :default facet,
   otherwise activate the :if-neede demon"
  [frame slot]
  (let [result (or (fget-v-d frame slot) (fget frame slot :if-needed))]
    (if (function? result) (result frame slot) result)))

(defn fget-i [frame slot]
"Fetches :value information from the :isa frames of a given frame and slot"
(defn fget-i1[frames slot]
   (if (nil? frames)
       nil
       (if-let [value (fget (eval (first frames)) slot :value)]
          value
          (recur (next frames) slot))))
  (if-let [classes (fget frame :isa :value)]
    (if (not(list? classes))
       (fget (eval classes) slot :value)
       (fget-i1 classes slot))
    nil))