emacs/lisp/emacs-lisp/pp.el

;;; pp.el --- pretty printer for Emacs Lisp

;; Copyright (C) 1989, 1993 Free Software Foundation, Inc.

;; Author: Randal Schwartz <merlyn@stonehenge.com>

;; This file is part of GNU Emacs.

;; GNU Emacs is free software; you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation; either version 2, or (at your option)
;; any later version.

;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs; see the file COPYING.  If not, write to the
;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
;; Boston, MA 02111-1307, USA.

;;; Code:
(defgroup pp nil
  "Pretty printer for Emacs Lisp."
  :prefix "pp-"
  :group 'lisp)

(defcustom pp-escape-newlines t 
  "*Value of `print-escape-newlines' used by pp-* functions."
  :type 'boolean
  :group 'pp)

(defun pp-to-string (object)
  "Return a string containing the pretty-printed representation of OBJECT.
OBJECT can be any Lisp object.  Quoting characters are used as needed
to make output that `read' can handle, whenever this is possible."
  (save-excursion
    (set-buffer (generate-new-buffer " pp-to-string"))
    (unwind-protect
	(progn
	  (lisp-mode-variables nil)
	  (set-syntax-table emacs-lisp-mode-syntax-table)
	  (let ((print-escape-newlines pp-escape-newlines)
		(print-quoted t))
	    (prin1 object (current-buffer)))
	  (goto-char (point-min))
	  (while (not (eobp))
	    ;; (message "%06d" (- (point-max) (point)))
	    (cond
	     ((condition-case err-var
		  (prog1 t (down-list 1))
		(error nil))
	      (save-excursion
		(backward-char 1)
		(skip-chars-backward "'`#^")
		(when (and (not (bobp)) (= ?\ (char-before)))
		  (delete-char -1)
		  (insert "\n"))))
	     ((condition-case err-var
		  (prog1 t (up-list 1))
		(error nil))
	      (while (looking-at "\\s)")
		(forward-char 1))
	      (delete-region
	       (point)
	       (progn (skip-chars-forward " \t") (point)))
	      (insert ?\n))
	     (t (goto-char (point-max)))))
	  (goto-char (point-min))
	  (indent-sexp)
	  (buffer-string))
      (kill-buffer (current-buffer)))))

;;;###autoload
(defun pp (object &optional stream)
  "Output the pretty-printed representation of OBJECT, any Lisp object.
Quoting characters are printed as needed to make output that `read'
can handle, whenever this is possible.
Output stream is STREAM, or value of `standard-output' (which see)."
  (princ (pp-to-string object) (or stream standard-output)))

;;;###autoload
(defun pp-eval-expression (expression)
  "Evaluate EXPRESSION and pretty-print value into a new display buffer.
If the pretty-printed value fits on one line, the message line is used
instead.  The value is also consed onto the front of the list
in the variable `values'."
  (interactive "xPp-eval: ")
  (setq values (cons (eval expression) values))
  (let* ((old-show-function temp-buffer-show-function)
	 ;; Use this function to display the buffer.
	 ;; This function either decides not to display it at all
	 ;; or displays it in the usual way.
	 (temp-buffer-show-function
	  (function
	   (lambda (buf)
	     (save-excursion
	       (set-buffer buf)
	       (goto-char (point-min))
	       (end-of-line 1)
	       (if (or (< (1+ (point)) (point-max))
		       (>= (- (point) (point-min)) (frame-width)))
		   (let ((temp-buffer-show-function old-show-function)
			 (old-selected (selected-window))
			 (window (display-buffer buf)))
		     (goto-char (point-min)) ; expected by some hooks ...
		     (make-frame-visible (window-frame window))
		     (unwind-protect
			 (progn
			   (select-window window)
			   (run-hooks 'temp-buffer-show-hook))
		       (select-window old-selected)))
		 (message "%s" (buffer-substring (point-min) (point)))
		 ))))))
    (with-output-to-temp-buffer "*Pp Eval Output*"
      (pp (car values)))
    (save-excursion
      (set-buffer "*Pp Eval Output*")
      (emacs-lisp-mode)
      (make-local-variable 'font-lock-verbose)
      (setq font-lock-verbose nil))))

;;;###autoload
(defun pp-eval-last-sexp (arg)
  "Run `pp-eval-expression' on sexp before point (which see).
With argument, pretty-print output into current buffer.
Ignores leading comment characters."
  (interactive "P")
  (let ((stab (syntax-table)) (pt (point)) start exp)
    (set-syntax-table emacs-lisp-mode-syntax-table)
    (save-excursion
      (forward-sexp -1)
      ;; If first line is commented, ignore all leading comments:
      (if (save-excursion (beginning-of-line) (looking-at "[ \t]*;"))
	  (progn
	    (setq exp (buffer-substring (point) pt))
	    (while (string-match "\n[ \t]*;+" exp start)
	      (setq start (1+ (match-beginning 0))
		    exp (concat (substring exp 0 start)
				(substring exp (match-end 0)))))
	    (setq exp (read exp)))
	(setq exp (read (current-buffer)))))
    (set-syntax-table stab)
    (if arg
	(insert (pp-to-string (eval exp)))
      (pp-eval-expression exp))))

;;; Test cases for quote
;; (pp-eval-expression ''(quote quote))
;; (pp-eval-expression ''((quote a) (quote b)))
;; (pp-eval-expression ''('a 'b))	; same as above
;; (pp-eval-expression ''((quote (quote quote)) (quote quote)))
;; These do not satisfy the quote test.
;; (pp-eval-expression ''quote)
;; (pp-eval-expression ''(quote))
;; (pp-eval-expression ''(quote . quote))
;; (pp-eval-expression ''(quote a b))
;; (pp-eval-expression ''(quotefoo))
;; (pp-eval-expression ''(a b))

(provide 'pp)				; so (require 'pp) works

;;; pp.el ends here.