maybe-stupid-repl.clj

(def eval-context (atom {}))

(defn handle
  "Imaginary message handler that sets the namespace received out of band."
  [ns]
  (swap! eval-context assoc #'*ns* (find-ns ns)))

(defn repl
  []
  (loop []
    ,,,
    ;; `in` is a LineNumberingPushbackReader wrapping a socket
    ;; Block until there's something to read, then read maybe one character.
    (let [n (.read in)
          ;; Now that we're no longer blocked, set the ns to the ns we received
          ;; out of band.
          _ (set! *ns* (get @eval-context #'*ns* (the-ns 'user)))
          ;; Unread however many chars we read earlier
          _ (.unread in n)
          ;; Proceed as usual.
          [form s] (read+string ,,, in)
          ,,,]
          (eval form)
          ,,,)))