Clementson's Blog

A useful function when working with Scheme in Emacs - Eval DWIM

Thursday, December 4, 2003

When I'm working with Scheme in Emacs, I find the following function quite useful:

;; "Do What I Mean" evaluation
(defun scheme-send-dwim (arg)
  "Send the appropriate forms to Scheme to be evaluated."
  (interactive "P")
  (save-excursion
    (cond 
     ;;Region selected - evaluate region
     ((not (equal mark-active nil))
      (scheme-send-region (mark) (point)))
     ;; At/after sexp - evaluate last sexp
     ((or (looking-at "\s)")
	  (save-excursion
	    (backward-char 1)
	    (looking-at "\s)")))
      (if (looking-at "\s)")
	  (forward-char 1)) 
      (scheme-send-last-sexp))
     ;; At/before sexp - evaluate next sexp
     ((or (looking-at "\s(")
	  (save-excursion
	    (forward-char 1)
	    (looking-at "\s(")))
      (if (looking-at "\s(")
	  (forward-list 1)) 
      (scheme-send-last-sexp))
     ;; Default - evaluate enclosing top-level sexp
     (t (scheme-send-definition)))
    (if arg (switch-to-scheme t))))

• If a region has been selected, evaluate the region
• If the cursor is positioned on or directly after a closing parens, evaluate the preceeding s-expression
• If the cursor is positioned on or directly before an openning parens, evaluate the following s-expression
• Otherwise, evaluate the top level s-expression that the cursor is located inside of

(add-hook 'scheme-mode-hook
	  (lambda ()
	    (interactive)
	    (define-key scheme-mode-map [(control c) (x)] 'scheme-send-dwim)))

(add-hook 'Info-mode-hook
	  '(lambda ()
	     (interactive)
	     (define-key Info-mode-map [(control c) (x)] 'scheme-send-dwim)))