Re: Emulation of XSL's id() in DSSSL?

[Norman Walsh <ndw@xxxxxxxxxx>]

/ Ralf Kempkens <kempkens@xxxxxxxxxxx> was heard to say:
| Thank you Norman, but you haven't got my point;

Oops. Right you are. Sorry about that.

| That's just the problem. I want to support multiple
| references. So I need a scheme function that breaks up a
| string into a list, using space as separator.  But my Scheme
| knowledge doesn't go that far.

This is from dblib.dsl:

(define (split str #!optional (whitespace '(#\space)))
  ;; REFENTRY split
  ;; PURP Splits string at whitespace and returns the resulting list of tokens
  ;; DESC
  ;; Given a string containing delimited tokens, return a list
  ;; of the tokens in string form.
  ;; ARGS
  ;; ARG 'str'
  ;; The string to split.
  ;; /ARG
  ;; ARG 'whitespace' o
  ;; A list of characters that should
  ;; be treated as whitespace.
  ;; /ARG
  ;; /ARGS
  ;; /DESC
  ;; AUTHOR David Megginson
  ;; EMAIL dmeggins@xxxxxxxxxx
  ;; /REFENTRY
  (let loop ((characters (string->list str)) ; Top-level recursive loop.
	     (current-word '())
	     (tokens '()))

    ; If there are no characters left,
    ; then we're done!
    (cond ((null? characters)
	   ; Is there a token in progress?
	   (if (null? current-word)
	       (reverse tokens)
	       (reverse (cons (list->string (reverse current-word))
			      tokens))))
	  ; If there are characters left,
	  ; then keep going.
	  (#t
	   (let ((c (car characters))
		 (rest (cdr characters)))
	     ; Are we reading a space?
	     (cond ((member c whitespace)
		    (if (null? current-word)
			(loop rest '() tokens)
			(loop rest
			      '()
			      (cons (list->string (reverse current-word))
				    tokens))))
		   ; We are reading a non-space
		   (#t
		    (loop rest (cons c current-word) tokens))))))))

Having split the string into a list of tokens, you now want to build
a nodelist of the targets, so something like this ought to work (totally
untested...)

(let loop ((idstrlist (split (attribute-string "references")))
           (targets (empty-node-list)))
  (if (null? idstrlist)
      targets
      (loop (cdr idstrlist)
            (nodelist targets (element-with-id (car idstrlist))))))

                                        Be seeing you,
                                          norm

-- 
Norman Walsh <ndw@xxxxxxxxxx>      | In a universe of electrons and
http://nwalsh.com/                 | selfish genes, blind physical
                                   | forces and genetic replication,
                                   | some people are going to get hurt,
                                   | other people are going to get
                                   | lucky, and you won't find any
                                   | rhyme or reason in it, nor any
                                   | justice.--Richard Dawkins


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