Re: how to use parsing expressing grammar

[Xah Lee <xahlee@gmail.com>]

Hi Helmut,

another question i have is, how do i capture text as in regex's “\(...
\)”, “\1”?

I know in your elisp header file it mentions

;;  (action FORM)          ; evaluate FORM
;;  `(VAR... -- FORM...)   ; stack action

how do i capture match using that?

e.g. to match

<img src="some.png" alt="pretty" width="33" height="33" >

(defun doMyReplace ()
(interactive)
  (peg-parse
   (imgTag "<img" _ (+ attributes _) ">")
   (attributes (or src alt width height))
   (src "src" _* "=" _* "\"" filePath "\"")
   (filePath (+ [A-Z a-z "./_-"]))
   (alt "alt" _* "=" _* "\"" altStr "\"")
   (altStr (* [A-Z a-z "./ '_"]))
   (width "width" _* "=" _* "\"" digits "\"")
   (height "height" _* "=" _* "\"" digits "\"")
   (_* (* ["\n \t"])) ; 0 or more white space
   (_ (+ ["\n \t"])) ; 1 or more white space
   (digits (+ [0-9]))
   )
)

suppose i want to swap the src and alt text and have

<img src="pretty" alt="some.png" width="33" height="33" >

Thanks.

  Xah
∑ http://xahlee.org/

☄