specificity.clj

(def conf {:people [{:lang :clojure}, {:lang :ruby}, {:lang :m4}]})

(defn clojurists
  "Returns all clojurists at a conference."
  [conf]
  (filter #(= :clojure (:lang %)) (:people conf)))

(defn final-person
  "Returns the last attendee to the conference."
  [conf] 
  (peek (:people conf)))

; Often in my code, most functions work on any collection type, and users are expected
; to pass in any collection. I may convert back and forth between lazy seqs and vecs
; internally, as I massage the collection into the right shape to answer some question.
; This means that some functions performance (e.g. with nth), and in other cases
; correctness (e.g. with peek/push/pop) depends on whether the collection is a vector
; or not. I'd like my types to enforce this, but only where it matters, rather than
; require :people *always* be a vector.