is-acii.clj

(defn is-ascii-alpha-num [c]
  (let [n (Character/getNumericValue (char c))]
    (or (and (>= n (char-val \a)) (<= n (char-val \z)))
        (and (>= n (char-val \A)) (<= n (char-val \Z)))
        (and (>= n (char-val \0)) (<= n (char-val \9)))))

parse-tree.clj

[:program 
  [:binary-exp 
    :minus 
    [:binary-exp
      :add 
      [:value [:int 1]] 
      [:value [:int 2]]] 
    [:unary-exp 
      :length 
      [:value [:string "hello"]]
    ]
  ]
]

square.clj

(defn square [x]
  (* x x))