Clojure implementation of the Feature Comparison Mini-Exercise from Common Lisp: A Gentle Introduction to Symbolic Computing

core.clj

(ns compare-descriptions.core
  (:require [clojure.set :only intersection]))

(defn- right-side
  "Given a list containing the descriptions of two objects separated by the
   keyword :-vs-, return the description of the object to the right of the
   separator."
  [descriptions]
  (rest (drop-while #(not= % :-vs-)
          descriptions)))

(defn- left-side
  "Given a list containing the descriptions of two objects separated by the
   keyword :-vs-, return the description of the object to the left of the
   separator."
  [descriptions]
  (take-while #(not= % :-vs-)
    descriptions))

(defn count-common
  "Given a list containing the descriptions of two objects separated by the
   keyword :-vs-, return the count of features the two objects have in common."
  [descriptions]
  (count (clojure.set/intersection (set (left-side descriptions))
                                   (set (right-side descriptions)))))

(defn compare-features
  "Given a list containing the descriptions of two objects separated by the
   keyword :-vs-, return a description of the number of features the two
   objects have in common."
  [descriptions]
  (str (count-common descriptions) " common features"))