axial-tree-grammar.clj

(def axial-tree-a {:start     [\F]
                   :rules     {\F "F[+F]F[-F]F"}
                   :angle     25.7
                   :constants #{\F \+ \- \[ \]}
                   :cmd-map   {\F :forward
                               \+ :left
                               \- :right
                               \[ :push
                               \] :pop}})

generate.clj

(defn apply-rules [grammar pattern]
  (apply str
         (replace (:rules grammar) pattern)))

(defn gen-commands [grammar n]
  (nth
    (iterate
      (partial apply-rules grammar) (:start grammar))
    n))