I want to create a table in org-mode and use it in Ditaa The following function is created to replace “^+-” to “|-” and similarly, “^-+\s-*” to “-|”.

Surprisingly, this does not work.

(defun ditaa-to-table (begin end)
  "Replace “^\+-” to “|-” in region; Replace “-\+\s-*$” to “-|”"
  "I want to create a table in org-mode and use it in Ditaa"
  "org-mode uses |- and -| for the row/cell delimiter at the extremes of the     line, while Ditaa uses +- and -+"

  (interactive "r")
    (narrow-to-region begin end)

    (goto-char (point-min))
    (while (search-forward-regexp "^\s-*\+-" nil t) (replace-match "|-" nil t))

    (goto-char (point-min))
    (while (search-forward-regexp "-\+\s-*$" nil t) (replace-match "-|" nil t))


If I use,

(while (search-forward-regexp "\+-" nil t) (replace-match "|-" nil t)) ;; works

works, But once I add the "^\s-*" char to mark the start-of-line, it stops working.

Similarly, basic one works, but once the "\s-*$" is added, it stops working

(while (search-forward-regexp "-\+" nil t) (replace-match "-|" nil t)) ;; works
(while (search-forward-regexp "-\+\s-*$" nil t) (replace-match "-|" nil t)) ;; does not work

I tried posix-search-forward also, and it does not work.

  • 1
    Double escape your special characters.
    – Dan
    Apr 10, 2017 at 4:38
  • Thanks. Not only that, I have to replace \s with [:space:]. Re-Builder helped me build the right RegExp that can be used in the function. Apr 10, 2017 at 6:09

1 Answer 1


You're getting tripped up by the escaping requirements for Emacs regexps when expressed in the double-quoted read syntax for strings, in conjunction with some historical-compatibility behaviour in Emacs' regexp engine.

Regarding the syntax requirements for special characters, please refer to these other Q&As:

(The last one covers the issue in the context of the re-builder feature of Emacs, which is extremely useful.)

The reason your simpler initial regexp was working at all is explained in C-hig (elisp) Regexp Special as follows:

*Please note:* For historical compatibility, special characters are
treated as ordinary ones if they are in contexts where their special
meanings make no sense.  For example, ‘*foo’ treats ‘*’ as ordinary
since there is no preceding expression on which the ‘*’ can act.  It is
poor practice to depend on this behavior; quote the special character
anyway, regardless of where it appears.

"\+-" evaluates to +- which you are using as a regexp. + is normally special, but in that pattern is being treated the same as the regexp \+-, which in string read syntax would be written as "\\+-".

"^\s-*\+-" on the other hand evaluates to ^ -*+- which is certainly not the regexp you were intending.

See C-hig (elisp) Basic Char Syntax for why "\s" is a space.

  • Thanks a lot. re-builder helped me to solve the problem. Apr 10, 2017 at 6:04

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.