Execute Scala code from within Emacs

Question

Scala REPL is great for short expressions, but multi-line expressions are difficult to edit, especially if there some syntax error somewhere, it requires reissuing the statements line by line.

On the other hand Emacs scala-mode2 looks nice, it would be awesome if I could just select a region of the buffer and send it to Scala REPL, and see the results in a minibuffer.

Is this possible? Googling didn't produce any positive answer. or do you think this would be an useful feature?

If I were to implement this, what would be the best approach? I was thinking that I could just have a Scala REPL running in the background and interacting with it via std in/out from Emacs.

Answer 1

Just in case anyone is interested, the below Emacs script will evaluate the region in the Scala REPL.

(defun eval-scala (start end)
  (interactive (list (point) (mark)))
  ;; start scala if it hasn't started yet
  (unless (get-process "scala-repl")
    (let ((process-connection-type nil))  ; use a pipe
      (start-process "scala-repl" "*scala*"  "scala"))
    (set-buffer "*scala*")
    (special-mode)
    )  
  ;; execute
  (process-send-region "scala-repl" start end)
  (process-send-string "scala-repl" "\n")
  ;;display buffer
  (display-buffer 
   (get-buffer "*scala*")
   '((display-buffer-reuse-window
      display-buffer-pop-up-window
      display-buffer-pop-up-frame)
     (reusable-frames . 0)
     (window-height . 8) (window-width . nil)     
   )
  )
)

Bind the above eval-scala function to your preferred short-cut key, e.g.

(global-set-key (kbd "C-e") 'eval-scala)