World: r3wp

and as that's the most difficult part i don't really undersand it 
 so we will see any help is welcome anyway.

for me and that's probably a noob though becasuse i'm not a guru... 
but none rule and string rule avec  almost the same effect isolating 
and spliting items of a string and arranging it into a returned block!


but yes the bigest part will be to explain the block rule the parse 
in a  block rule instructions
(copy at thru to etc...)

i will have to explain any some end newline all those kind of things 
that annimate parse and make it completly another thing compared 
to regular expression

Gregg well ... i'm not against contributing but I think one of the 
good way is for lower ranked programmer to express their problems 
and try to construct a doc helped by gurus to answers their ask then 
if it's readable and understandable by me I assum anyone could understand 
it 

My point is once people end rading the doc they will say "yeah i 
understoud what it's all about so now lets play with parse :P" if 
that only goal can be achieve I think a big step will be done.

and parse is something I really want to use in extensiv ways and 
if in the process i can acquiere enough knowledge and sahre it then 
we will all benefit from that

shadwolf... just found this nice little tutorial...  :-)

http://compsci.ca/v3/viewtopic.php?t=17706

Can anyone explain the error indicated in the last comment?

You should define a complement to spaces and then change the parse 
rule to copy the complementary characters.

The changed rule has

	copy varb to spaces


Note: that's *to* spaces, not *thru* spaces. That is, the spaces 
are not consumed like they were in the previous rule.
If you have a rule

	spaces

then those spaces will be consumed.
If you have a rule

	to spaces


then the parse index will be moved to the head of those spaces, so 
the spaces themselves will not be consumed.

So if you want the spaces also to be consumed (the parse index to 
be advanced through them), then you need a rule:

	to spaces spaces

That's right, you have to repeat yourself a little bit.

So the fixed version of the broken rule from the article should be:

	rule: ["a" spaces copy varb to spaces spaces "c"]

(Feel free to post this answer to the article.)

no, I see it differently.

the problem is that spaces is  " [some spacer]" , and R2 does not 
allow  "to subrule".

You are right. (I was so confident I didn't test my code. Good thing 
nobody posted it.)

Ok, this is tested:

.
	spacer: charset " ^-^/"  ; Space, tab, newline.

 non-spacer: complement spacer ; All chars except the three above.
	whatever: [some non-spacer]
	spaces: [some spacer]
	rule: ["a" spaces copy varb whatever spaces "c"]
	parse/all "a b c" rule ;== true

Maybe someone who subscribed can post this code, with additional 
comments:

The above problem reduces to:

	spacer: charset " "
	parse/all " " [to spacer]
	
	** Script Error: Invalid argument: make bitset! #{
	0000000001000000000000000000000000000000000000000000000000000000
	}
	** Near: parse/all " " [to spacer]

The reason is Rebol2 parse does not allow "to subrule".
(Pointed out by sqlab, thanks.)
	
Here's a way to do it using COMPLEMENT (suggested by Graham):
	
	spacer: charset " ^-^/"  ; Space, tab, newline.

 non-spacer: complement spacer ; All chars except the three above.
	whatever: [some non-spacer]
	spaces: [some spacer]
	rule: ["a" spaces copy varb whatever spaces "c"]
	parse/all "a b c" rule ;== true

Anton, this sounds like that question asked on stackoverflow.com, 
linked earlier here in this group.

You're right. Some guy has been cross-posting the same question.

Oh, and I see you gave a good reply in the stackoverflow.com site.

Hi All,  I'm new to PARSE, so I've come here to learn a little more. 
 I'm working on and off on a little testing project of my own for 
R3.

My goal is to navigate through some website(s), capture Rebol code, 
and the expeceted responses such as this page: 
http://rebol.com/r3/docs/functions/try.html

I'd like to capture the text inside a block like this:
[ "cmd" {if error? try [1 + "x"] [print "Did not work."]}
rsp
   {Did not work.} 
cmd
  {if error? try [load "$10,20,30"] [print "No good"]}
rsp
  {No good}]


Can anyone point me to some parse example code which can "tear apart" 
an HTTP page based on text and the type of text?

I realize I may be biting off a bit more than I can chew, but I'd 
still like to give it a try.
Thanks in advance.

You can just set your block that you want to parse to a word.  Such 
as:

blk: [ "cmd" {if error? try [1 + "x"] [print "Did not work."]}
rsp
   {Did not work.} 
cmd
  {if error? try [load "$10,20,30"] [print "No good"]}
rsp
  {No good}]

; and then do this:

>> parse blk [some [set s string! (print s)]]

Hi Paul,  I may have mis-stated what I'm after.  You see the site 
 http://rebol.com/r3/docs/functions/try.htmlhas displayable rebol 
code and responses within the html.  If you captured the html code 
you would find something like this:
<html>
<head>
...(additional html code and text)...

<title>REBOL 3   Functions: try</title>TRY returns an error value 
if an error happened,
otherwise it returns the normal result of the block.</p>

<pre>if error? try [1 + "x"] [print "Did not work."]             
                    <-- in this e.g. the tag <pre> will preceed the 
rebol command until the next tag

<span class="eval">Did not work.</span></pre>                    
      <-- the tag <span class="eval">  will preceed the response 

<pre>if error? try [load "$10,20,30"] [print "No good"]          
          <-- this is the next rebol command

<span class="eval">No good</span></pre>                          
       <-- this is the next response
<h2 id="section-3">Related</h2>


I want to be able to interrogate the html code, parse it and capture 
the rebol commands and responses (if any), then put that into your 
above block example.

I have this code which does this:

cmd-txt: "unasg"  cmd-term: "<"

pre-txt: "unasg"  pre-bgn:  "<pre>"               pre-end: "</pre>"

rsp-txt: "unasg"  rsp-bgn:  {<span class="eval">} rsp-end: {</span>}
site-url:	http://rebol.com/r3/docs/functions/try.html

page-txt: to-string read site-url
probe parse page-txt [thru pre-bgn copy pre-txt to pre-end]
probe parse pre-txt  [copy cmd-txt to cmd-term]
probe parse pre-txt  [thru rsp-bgn copy rsp-txt to rsp-end]

print [{"cmd"} "{" cmd-txt "}"]
print [{"rsp"} "{" rsp-txt "}"]

will yield this:
cmd

 { if error? try [1 + "x"] [print "Did not work."]          <-- this 
 is close to what I want to do
}
rsp
 { Did not work. }


This is close to what I want, but it is not foolproof.  For example, 
I would like to capture all displayable text that is separated from 
any html tags.  In my code example, if a displayable greater than 
symbol  < was displayed, then the parse would stop prematurely.


I am guessing someone has already created some code to "pull apart" 
a html web page, separating displayable text from invisible markup 
code.

p.s.  I'm doing this in R3!

I think I may have found an example on REBOL.ORG called WebSplit.r 
 that may be helpful.  I welcome any other suggestions.

load/markup

more to what Graham is saying is, try...
>> load/markup http://rebol.com/r3/docs/functions/try.html


you will be returned a block of strings and tags, which you could 
use the tag? word to test if each element is a tag or not to seperate 
HTML from regular Strings.

This should help with the parse itself...
parse page-txt [
	thru pre-bgn 
	copy cmd-txt 
	to rsp-bgn
	thru rsp-bgn
	copy rsp-term 
	to rsp-end 
	(print ["Cmd: " cmd-txt "RSP: " rsp-term])
	to end
]

which would return...
Cmd:  if error? try [1 + "x"] [print "Did not work."]
RSP:  Did not work.
== true

sorry, missed the quotes around the returned set...
parse page-txt [
	thru pre-bgn 
	copy cmd-txt 
	to rsp-bgn
	thru rsp-bgn
	copy rsp-term 
	to rsp-end 
	(print ["Cmd: " mold cmd-txt "RSP: " mold rsp-term])
	to end
]

which would return...
Cmd:  {if error? try [1 + "x"] [print "Did not work."]
} RSP:  "Did not work."

if you want the RSP line on a separte line from the '{', then put 
a  the word   newline   before the string "RSP: ", or use  "^/RSP: 
", where the   "^/" is equivalent to a newline or carriage return.

with the result...
Cmd:  {if error? try [1 + "x"] [print "Did not work."]
}
RSP:  "Did not work."

if you want to capture multiple command and response blocks you wrap 
the parse block in...
any[ parse statements] 

.... excluding the to end statement which you would want to include 
only after   'any'   parse instances occured.

parse page-txt [
	any[
		thru pre-bgn 
		copy cmd-txt 
		to rsp-bgn
		thru rsp-bgn
		copy rsp-term 
		to rsp-end 
		(print ["Cmd: " mold cmd-txt "^/RSP: " mold rsp-term])
	]
	to end
]

Excellent suggestions Brock and Graham -- That gives me a lot to 
play with!!  Thank you.

Does someone know of some scripts that parse documents written in 
LaTex.  I would need examples applying parse to the LaTex language.

What about parsing another similar language?

http://www.rebol.org/view-script.r?script=qml-base.r

This is ell written too http://www.codeconscious.com/rebol/parse-tutorial.html

Thanks for those references.

Parse question on StackOverflow -- not yet answered:

http://stackoverflow.com/questions/1415340/rebol-parsing-rule-how-to-correct-the-rule-to-separate-paragraphs

Three answers now.

Steeve - move parse discussion here.

So... does such a function take an argument, such as the current 
index for the series being parsed?

That's how REPLACE works...

REPLACE?

i would say, no functions with parameters allowed

but if you can perform a do/next then parameters are allowed

Yeah. If you pass a function as the replacement value, that function 
will be called with the series at the replacement position as a parameter, 
and its return value is used. ARRAY does something similar too. My 
changes.

Say that the series position parameter is passed with APPLY rules. 
If the function takes a parameter it sees it; if not it doesn't.

Or we can provide 2 index by default, maintained by the parse engine.
& = the head of last rule matched
&&= the tail of the last matched rule.