Basic Functional building blocks- map, filter, reduce, etc ab initio in clojure

fn-prog.clj

(defn map 
  "(map f coll) takes a function f and applies it to each element in coll and returns a collection"
  ([f coll] (map f coll []))
  ([f coll acc]
   (if (empty? coll)
     acc
     (map f (rest coll) (cons (f (first coll)) acc)))))

(defn filter
  "(filter f coll) takes a function f that computes a predicate condition on each element in coll and filtered collection is returned"
  ([f coll] (filter f coll []))
  ([f coll acc]
   (if (empty? coll)
     acc
     (if (f (first coll))
       (filter f (rest coll) (cons (first coll) acc))
       (filter f (rest coll) acc)))))