World: r3wp

obviously you could use (p: back p)

Even better. Thanks Anton. Seems that "-1 skip" should not be that 
hard to implement

parse "aaa" [some [p: "a"] :p "a"]

I think this needs (p: back p) before :p.

Not in my version. The p is set before the position advances past 
the "a", so it is already back.

The p is reset before "a" is consumed - that is why I put [p: "a"] 
in [].

So why it does return 'false here? p is empty on :p.

Interesting. It seems to be setting the last p before it fails on 
the last iteration of "a".

Clearly I need a temporary.

parse "aaa" [some [p1: "a" (p2: :p1)] :p2 "a"]

I have done this sort of thing before.

temporary, or step back

A temporary will work better with parts of unknown size, and be faster 
too.

OK

Still, you might want to apply rewrite rules to your generated parse 
rules - that code seems a little sloppy.

Peephole fixing?

rewrite rules?

that you will not have [some "a" "a"] but just [some "a"]

Well, I'm not exactly sure if that's possible, I have to do some 
tests

By rewrite rules, I mean something like what Gabriele came up with 
for the rebcode assembler a while ago. Since I helped refine his 
work, I may still have a copy somewhere. I'll take a look.

I'm not sure I helped with this one, now that I think of it. It's 
one of his literate programming projects, here:
http://www.colellachiara.com/soft/Misc/
Look for rewrite.*

that one is different from the one in rebcode, but the principle 
is about the same.

OK I'll check it, thanks

is it possible to convert bitset! back to something readable?

Define readable! ;-) Maybe you could use a combination of to-string, 
to-binary, debase and things like that.

if i do (a: charset "abc") i want to do also (decharset a) to get 
"abc" :) that's readable ;)

loop thru all possible chars, print matches ;)

yes, but that's really not the fastet way :)

Rebolek, use my hokus-pokus function:

hokus-pokus: func [
	value
	/local a out
][
	either bitset? value [
		a: enbase/base to-binary value 2
		out: copy ""
		forall a [
			if a/1 = #"1" [append out to-char (index? a) - 4]
		]
		out
	][
		42
	]
]

>> a: charset "abc"
>> hokus-pokus a
== "abc"

bitset-to-string: func [b [bitset!] /local s] [
    s: copy ""
    repeat x 256 [
        x: to-char x - 1
        if find b x [append s x]
    ]
    s
]

; Sorry, error...
bitset-to-string: func [b [bitset!] /local s x c] [
    s: copy ""
    repeat x 256 [
        c: to-char x - 1
        if find b c [append s c]
    ]
    s
]

That should be pretty fast, and it doesn't involve huge binary temporaries.

http://www.codeconscious.com/rebol/scripts/bitsets.r

To compare those, it looks like

    repeat x 256 [
        c: to-char x - 1
        if find b c [append s c]
    ]

would be faster than

    for i 0 255 1 [

        if parse/all to-string test-char: to-char i reduce [ bitset ] [
            append result test-char
        ]
    ]


because of the reduce, the to-string. the parse, and the use of the 
mezzanine for instead of the native repeat.

Your's is more flexible, though.

Lots of other interesting stuff on that site.

Yes, Brett has built a lot of very cool stuff. Haven't seen him around 
for a while though.

So, this is my first attempt to do regular expressions in REBOL. 
Type on your console:
do http://bolek.techno.cz/reb/regex.r

Some things are missing and it can sometimes run in endless loop 
when it shouldn't, so please be benevolent :)

But at least the email regex can be translated and parsed succesfully.

it's quite small

nice:)... just you should print regex not regexp in the example (or 
rename the function)

and... it would be good to have just a function which returns the 
translated Rebol parse block

regex rules look quite complicated!

Graham yes, they are :)

Oldes: regex vs. regexp on google is 12mil vs 8mil, so that's the 
reason, but I can rename it (it was called regexp yesterday ;)

And yes, function returning just parse rules will be done, this is 
just a work in progress

I don't mind how you caal the function.. just the printed one is 
different from the one used which is confusing as first what I did 
was copy and paste what you printed and got en error that regexp 
function do not exists

and anyway... 12 or 8 millions google rusults  is not a big difference 
if your page is not listed between first 20 pages:)

oh I see now what you mean...that print is from test function, I'll 
change it. And that google score - I used it just to compare what 
name will be better, I in no way don't expect to be there with my 
page :) It's just what I do when I'm not sure how some word spells 
(svatba vs. svadba and so on ;) - I put both terms in Google and 
the one with better score is probably the right one ;)

you can use... http://www.googlefight.com/or make a Rebol version... 
it's quite easy

if you were talking about bitsets.... it reminded me that it would 
be good to have some common rules in Rebol3 available for parsing...