[REBOL] Re: Parse and and recursion local variables?
From: volker:nitsch:g:mail at: 17-Mar-2007 19:22
My typicall way to do that is my own stack.
stack: copy[]
parse rule[
(insert/only stack reduce[local1 local2])
rule ;recursion
(set[local local2] first stack remove stack)
]
On 3/17/07, Petr Krenzelok <petr.krenzelok-trz.cz> wrote:
> Hi,
>
> not being much skilled in parsing, I tried to do a little parser for my
> own rsp-tag system (I know there are few robust systems out there, but I
> want to learn via implementing my own). Basically the idea is to use
> kind of comment tags, which still allow web designer to display html
> content. The most attractive system for me was Gabriele's Temple, but it
> is not finished, nor supported, so I want my own one, much simpler :-)
> My tags look like:
>
> <!--[section-x]-->
> subsection html code
> <!--/[section-x]-->
>
> I want to detect particular sections and invoke particular modules/code
> for them, submitting it section content. Basically it works, but I also
> wanted to try my very primitive parser to do some recursion. And it
> seems to me I tracked down, why it does not work - inside of nested
> sections, when the recursive rule is applied, I think that
> rsp-section-name is not kept local to particular recursion level? Can I
> make it local by putting e.g. parse into function body, defining a word
> (rsp-tag-nested) as a local variable? Or the issue is more complex and
> my rules simply build insufficiently?
>
> Also - if I don't use to [a | b | c], as we don't have any ;-), I have
> to skip by one char. That makes stripping out html subsections a bit
> difficult (where to put correct markers), as my rsp-html or html rules
> simply are "1 skip". But maybe that could be solved by defining what the
> proper html charset is?
>
> Sorry if my questions are rather primitive to our parse gurus here :-)
>
> -pekr-
> ---------------------
> REBOL []
>
> template: {
> this is the beginning of html:-)
> <b><!--[mark-x]-->Hello x!<!--/[mark-x]--></b>
> <b><!--[mark-y]-->Hello y!<!--/[mark-y]--></b>
> <b><!--[mark-z]-->Hello z!<!--/[mark-z]--></b>
> <b><!--[mark-w]-->Hello w!
> another html code
> <!--[mark-u]-->
> subsection html code
> <!--/[mark-u]-->
> finishing mark-w html code
> <!--/[mark-w]--></b>
> this is the end :-)
> }
>
> out: copy ""
>
> ;--- uncommend following to get incorrect recursion behavior
> ;rsp-begin: ["<!--[" copy rsp-tag-name to "]-->" "]-->"]
> ;rsp-end: ["<!--/[" rsp-tag-name "]-->"]
>
> ;--- comment following if enabling above ones ...
> rsp-begin: ["<!--[" s: some [e: "]-->" (print copy/part s e) break | skip]]
> rsp-end: ["<!--/[" s: some [e: "]-->" (print copy/part s e) break | skip]]
>
> ;just to distinguish for eventual debugging ...
> html: [copy char skip (append out char)]
> rsp-html: [copy char skip (append out char)]
>
> rsp-section: [rsp-begin any [rsp-end break | rsp-section | rsp-html]
> ]
>
> rsp-rules: [any [rsp-section | html] end]
>
> parse/all template rsp-rules
>
> probe out
>
> halt
>
> --
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>
--
-Volker
Any problem in computer science can be solved with another layer of
indirection. But that usually will create another problem.
David
Wheeler
