[slime-devel] Evaluating elisp from lisp

Pascal J. Bourguignon pjb at informatimago.com
Tue Aug 3 12:41:46 UTC 2010

Sharad Pratap <sh4r4d at gmail.com> writes:
> I wanted to know is it possible in slime/swank to evaluate elisp code
> from lisp environment.
> Basically I need to do it in StumpWM(sbcl) environment, currently I am
> doing it through `emacs -e _form_' command and then prepending a quote
> at the start of output and then evaluating it in current lisp
> environment.

Yes, of course.

This worked with slime a few years ago.  I don't know if it still works.
;;;; emacs <-> common-lisp RPC with slime/swank

;;; In emacs, we can execute Common Lisp expressions:

(require 'slime)


(setf slime-enable-evaluate-in-emacs t) 

(defun eval-in-cl (cl-expression-string process-result-values)
   `(swank:eval-and-grab-output ,cl-expression-string)
   (lexical-let  ((here (current-buffer))
                  (process-result-values process-result-values))
     (lambda (result-values)
       (set-buffer here)
       (funcall process-result-values result-values)))))

(eval-in-cl "(values 1 * (ext:! 20) (package-name *package*))"
            (lambda (values)
              (dolist (v values)
                (insert (format "%s\n" v)))))
;; Returns:
;; nil
;; then later inserts:
;; 1
;; (42 (EMACS-UNREADABLE |buffer| |*scratch*|))
;; 2432902008176640000

;;; In Common Lisp, we can execute emacs lisp expressions:

(defparameter *emacs-readtable* (copy-readtable))
(setf (readtable-case *emacs-readtable*) :preserve)
(set-syntax-from-char #\> #\) *emacs-readtable*)
 #\# #\<
 (lambda (stream subchar dispchar)
   `(emacs-unreadable ,@(read-delimited-list #\> stream t)))

;; Probably more readtable patching would be in order.
;; We could define CLOS proxies for emacs objects for a more seamless
;; integration. swank::eval-in-emacs process the CL form to make it
;; "emacs" (eg. downcase symbols, etc).  It could convert CLOS proxies
;; to emacs lisp forms returning the corresponding emacs object.

(defun eval-in-emacs (form &optional nowait)
  (let ((result (SWANK::EVAL-IN-EMACS `(format "%S" ,form) nowait))
        (*readtable* *emacs-readtable*))
    (with-input-from-string (in result)
      (let ((result (read in nil in)))

(eval-in-emacs `(progn
                  (switch-to-buffer (buffer-named "*scratch*"))
                  (goto-char (point-max))
                  (insert ,(format nil "~%Hello~%"))
                  (list 42 (current-buffer))))

;; Switch to the *scratch* buffer,
;; goto the last position, and
;; inserts \nHello\n
;; then returns:
;; (42 (EMACS-UNREADABLE |buffer| |*scratch*|))

__Pascal Bourguignon__                     http://www.informatimago.com/

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