Generate car, cdr, cadr, cdar, etc. in Clojure

carcdr.clj

(ns semperos.hs
  (:require [clojure.string :as str]))

(defn strip-first-last
  "Strip first and last letter from string."
  [s]
  (subs (subs s 1) 0 (- (count s) 2)))

(def step-fns {\a first \d next})

(defmacro defcarcdr
  [name]
  (when-not (and (str/starts-with? (str name) "c")
                 (str/ends-with? (str name) "r"))
    (IllegalArgumentException. (str "defcarcdr expects car, cdr, cadr, etc., but you gave '" name "'.")))
  (let [steps (->> (strip-first-last (str name))
                   (map step-fns)
                   reverse)]
    `(def ~name (fn [coll#] (-> coll# ~@steps)))))

(defn defcarcdrs
  [num-steps]
  (doseq [n (reverse (range 1 num-steps))]
    (let [choices (into [] (for [x [\a \d]] x))
          fors (into [] (mapcat (fn [_] [(gensym) choices]) (range n)))]
      (doseq [combo (eval `(for ~fors (mapv first (partition 2 ~fors))))]
        (let [name (symbol (str "c" (apply str combo) "r"))]
          (eval `(defcarcdr ~name)))))))

(defcarcdrs 5)