World: r3wp

...except for the fact, that lit-words are used in the Do dialect 
(= when Rebol is concerned, as you say), when you want to write an 
expression, which evaluates to a specific word, so, e.g. the expression:

'a

evaluates to the same value as the expression:

first [a]

, which happens to be the word A

http://www.rebol.com/docs/core23/rebolcore-15.html#section-6

Depending on the situation, it can be hard to tell whether you are 
dealing with a word or a specific value. that's the price for freely 
interchangable code/data. :-)

a: [none]

b: copy a

b: reduce b ; me doing this behind your back

a
== [none] ; word!

b
== [none] ; none!

it is a bit difficult to understand recursive rules, but :-)

The difference between what I'm doing and what you linked to is that 
it's working against a string, while I'm doing a dialect, no?

I understood that character stuff wouldn't work in a dialect -- but 
my understanding is imperfect.

right, what you are doing is a dialect

OK. Thanks again for the timely help! I have to run off to work (which 
is firewalled up the yang), so you'll be able to avoid more silly 
questions from me for at least the next ten hours! ; - )

Dialect is a dialect. The only difference in string vs block parsing, 
imo is, that with block parsing, you are using REBOL datatypes to 
identify/match your types, whereas with string you are more "free-form" 
:-)

I know I was stopped by parse in some occasions where. I think always 
every time the problem would be solvable if I had for example >> 
to [ "A" | "B" ] where parser would check where is A and where is 
B and go to the closest one.

from Advocacy --> Graham [ to "A" | to "B" ] won't work as I want 
.. I will try to find a concrete example

this is a current parse limitation.

parse "start 111 end start 222 finish" [ some [ thru "start" copy 
NUMS [ to "finish | to "end" ] ] ]   this wont work

change it

[ to "end" | to "finish" ]

ok .. but I meant that you have "start 111 end start 222 finish start 
333 end "  then it won't work :)

change the rule again

I was trying to show an example where you have two possible endings 
and you want to process both (and you can differently with parens) 
) but you don't know in what order they will come or anything

In this case I would use block parsing ... then I'm no expert in 
parsing

parse string [ some [ "start" digits "end" | "start" digitis "finish 
]]

your problem is because you are using 'thru which breaks the other 
rule

yes , then you have to do charset parsing (but I don't know that 
yet :) ) .. I was just trying to say if there would be the way to 
say something like "to any [ "A" | "B" ] and it would go to the closest 
one A LOT of problems with parse would be easily solvable

you can use to but it still won't work

[ some [ "start" digits [ "end" | "finish" ] ]
should work

to go to the closest one .. means it has to try all the rules??

and see which has the best fit ?

no wgih is  the closest .. look at this example (I hope this will 
be better)

whigh = which

I know what you mean .. so you have to order your rules knowing what 
the data looks like

If you don't know what pattern the data is .. you can't parse it 
with anything.

parse "This is Apple . This is Windows ! This is Linux . This is 
Amiga ." [ some [ "This is" copy IT (print IT) to [ "." | "!" ] ]

The pattern is known ... the scentence starts with this is and can 
end with . or ! but they can come in any order .. if you try to parse 
with "." first you will get 
---- ops some errors upthere  .. just a sec

>> parse "This is Apple . This is Windows ! This is Linux . This 
is Amiga ." [
 some [ thru "This is" copy IT [to "." | to "!" ] (print IT) ]]
 Apple
 Windows ! This is Linux
 Amiga

this is the common to all problems where that I am describing .. 
if I had  > to [ "." | "!" ] and parse would find both and go to 
the one that is closer it would be solved.

charset [ #"!" #"." ]

ok , you again found a solution to my specific problem :))

BUT .. what if I want to have controll there .. or if for the sake 
of example it's a more complex multicharacter difference like "<DOT>" 
"<EXCLAMATION>"

Janko, best thing to do is show us a  string you can't parse ... 
and someone will show you how to do it.

>> parse "I like Apple . I like Windows ! I like Linux . I like Amiga 
." [

[     some [ thru "I like" copy IT [to "." ( prin "so so: ") | to 
"!" (prin "v
ery much: ") ] (print IT) ]]
so so:  Apple
so so:  Windows ! I like Linux
so so:  Amiga

I don't have real example right now :) I had them few times before 
and I also asked here about them and I solved with your help somehow

I just started talking about this as a general limitation of parse 
that I meed a lot of times and I suppose Paul could of meet it when 
trying to parse CSV

janko

,"some\"thing92!","graham" I am not sure but I think here you have 
the same problem

It's not necessarily a PARSE limitation, but there are things we'd 
like PARSE to do that aren't always reasonable. :-)


TO and THRU can work very well, but that doesn't mean they'll work 
for every situation. You may have to use rules where you check for 
your target value or just SKIP, marking locations in the input as 
you go.

CSV parsing is an issue, because REBOL handles some inputs well, 
but fails for what may be a common way things are formatted. "CSV" 
isn't always as simple as it sounds.

That said, if you know the format (e.g. WRT quotes and escapes), 
it can be done with PARSE. It just may not be a one-liner.

I know parsing csv can be messy ... at least at this high level I 
don't know how to do it with escapes and commas in etc

and I know everything has limitations ... this functionality OR with 
taking the first that appears would just in practice solve me many 
cases

you have to turn off parse's default delimiters and use bitsets

(aha bitsets.. I was calling them charsets upthere)

BTW, Bolek wrote a regex engine in Rebol ...