3. Cons the Magnificent

cons.clj

(defn rember [atom l]
  (loop [lat (seq l) res []]
    (if lat
      (let [f (first lat)]
        (if (= f atom)
          (next lat)
          (recur (next lat) (conj res f))))
      res)))

(defn firsts [lol]
  (loop [l (seq lol) res []]
    (if l
      (recur (next l) (conj res (first (first l))))
      res)))

(defn insertR [new old lat]
  (loop [l (seq lat) res []]
    (if l
      (if 
        (= (first l) old) (concat (conj res old new) (next l))
        (recur (next l) (conj res (first l))))
      res)))

(defn insertL [new old lat]
  (loop [l (seq lat) res []]
    (if l
      (if 
        (= (first l) old) (concat (conj res new)  l)
	(recur (next l) (conj res (first l))))
    res)))

(defn subst [new old lat]
  (loop [l (seq lat) res []]
    (if l
    (if 
      (= (first lat) old) (concat res (conj (next lat) new))
      (recur (next l) (conj res (first l))))
    res)))

(defn subst2 [new o1 o2 lat]
  (loop [l (seq lat) res []]
    (if l
      (if 
        (or (= (first l) o1) (= (first l) o2)) (concat res (conj (next l) new))  
        (recur (next l) (conj res (first l))))
      res)))

(defn multirember [a lat]
  (loop [l (seq lat) res []]
    (if l
      (if 
        (= (first l) a) (recur (next l) res)
        (recur (next l) (conj res (first l))))
      res)))

(defn multiinsertR [new old lat]
  (loop [l (seq lat) res []]
    (if l
      (if 
        (= (first l) old) (recur (next l) (conj res old new))
        (recur (next l) (conj res (first l))))
      res)))

(defn multiinsertL [new old lat]
  (loop [l (seq lat) res []]
    (if l
      (if
        (= (first l) old) (recur (next l) (conj res new old))
        (recur (next l) (conj res (first l))))
      res)))

(defn multisubst [new old lat]
  (loop [l (seq lat) res []]
    (if l
      (if 
        (= (first l) old) (recur (next l) (conj res new))
        (recur (next l) (conj res (first l))))
      res)))

Clojure functions for Chapter 3 of The Little Schemer.