gistfile1.clj

(defn pdf? [d]
  (= (type d) Document))

(defmacro with-pdf [bindings & body]
  (#'clojure.core/assert-args
   (vector? bindings) "A vector for its binding"
   (even? (count bindings)) "an even number of forms in binding vector")
  (cond
   (= (count bindings) 0) `(do ~@body)
   (symbol? (bindings 0)) `(if (pdf? ~(bindings 1))
                             (let ~(vector (bindings 0)
                                           `(doto ~(bindings 1) (.open)))
                               (try (with-pdf ~(subvec bindings 2) ~@body)
                                    (finally
                                     (. ~(bindings 0) close))))
                             (throw (IllegalArgumentException.
                                    "bind target must be a Document instance")))
   :else (throw (IllegalArgumentException.
                 "with-pdf only allows binding of Documents to Symbols"))))