stopping-let.clj

(defmacro let-stop [bindings & body]
  (if (some #{'*stop*} bindings)
    (let [stopped-bindings
          (->> bindings
               (take-while #(not= '*stop* %))
               vec)
          caught-symbols
          (->> stopped-bindings
               (partition 2)
               (map #(vector (keyword (first %)) (first %)))
               (into {}))]
      `(let ~stopped-bindings
         (throw (ex-info (str "Let was stopped at stage "
                              (/ (count ~stopped-bindings) 2))
                         {:current-symbols ~caught-symbols}))))
    `(let* ~(destructure bindings) ~@body)))

;; use

(let-stop [a 1
           b 2
           *stop*
           c 6
           ]
  (println a b c))

#_> (ex-data *e)
         
{:current-symbols {:a 1, :b 2}}