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World: r3wp

[Parse] Discussion of PARSE dialect

Brock
27-Jun-2007
[2009]
each being unique sub-rules
Steeve
27-Jun-2007
[2010x2]
yep, it's not limited
but when i say complex sub-rules , i mean that i have not to check 
single character only, but complex sentences
Brock
27-Jun-2007
[2012]
so the parse string would be better indicated something like "A B 
C" where each of those characters could be a sentence?
Steeve
27-Jun-2007
[2013]
yep
Brock
27-Jun-2007
[2014]
so this is close, with the exception that it does not allow for easy 
testing of unique terms being passed?
r1: "Sent frag 1"
r2: "Sent frag 2"
r3: "Sent frag 3"
r4: "Sent frag 4"

rule: [1 [r1 | r2 | r4 | r3]]


parse "Sent frag 1 sent frag 3 sent frag 4 sent frag 2" [[rule] [rule] 
[rule] [rule]]
Steeve
27-Jun-2007
[2015]
wrong, same problem ever, if it's the same sentence many time
Brock
27-Jun-2007
[2016]
yes, that's what I stated above, if it wouldn't allow for the same 
value to be passed twice, this would work.
Steeve
27-Jun-2007
[2017]
yep
Brock
27-Jun-2007
[2018x4]
I guess I don't understand why a unique function wouldn't work as 
a test prior to parsing.
;very basic example - 
unique: func [str][
	compare-set: "ABC"

 either "" = difference str compare-set [return true][return false]
]

;;;; and yes, that is very ugly
replace;   either "" =
with:   either empty?
... and of course 'unique shouldn't be used as a name due to Rebol 
already having a unique function.
Steeve
27-Jun-2007
[2022x2]
unique works for the rules which use simple constants, but i said 
it, i use more complex rules
parse data [all [rule1 | rule2 | rule3 | rule4]] 

all rules must apply 1 time and 1 time only  in any order, don't 
focus on what is inside rules (it contains sub-rules which contains 
sub-rules).
btiffin
27-Jun-2007
[2024]
Ok, this is convulted and probably wrong


rule: [copy res subrule (remove/part find subrule compse [| (res)] 
2)]
subrule: ["filler" | "a" | "b" | "c"]
parse "fillerabc" [4 [rule] end]


Remove the alternatives from the rule as you find them...the filler 
is to allow | "a" to be found.
Steeve
27-Jun-2007
[2025]
argh, this is uggly :-)
not better than my current solution using counters
btiffin
27-Jun-2007
[2026x2]
Yep...convoluted and hard to verify all the cases to boot.  :)  I 
wouldn't use it to be honest, but it was teasing my brain too much...
Now, I'll slowly back out of the room...ducking and dodging...  :)
Steeve
27-Jun-2007
[2028x2]
take a whisky on the rocks
i got a beer
Brock
27-Jun-2007
[2030x3]
This has it...
r1: "A"
r2: "B"
r3: "C"

rule: [opt [r1 r2 r3]]

parse "ABC" [[rule] [rule] [rule]]
opt = match zero or one time
don't ask me to explain it, but it seems to meet your sample requirements
Steeve
27-Jun-2007
[2033]
have you tested ? doesn't work at all for many cases
Brock
27-Jun-2007
[2034x3]
>> parse "BC" [[rule] [rule] [rule]]
== false
>> parse "ABC" [[rule] [rule] [rule]]
== true
>> parse "BBC" [[rule] [rule] [rule]]
== false
Steeve
27-Jun-2007
[2037x2]
parse "CBA"  = false
in any order, i said
Brock
27-Jun-2007
[2039]
damn, doesn't handle the varying order of elements
Steeve
27-Jun-2007
[2040]
:-)
btiffin
27-Jun-2007
[2041]
Yeah, this problem needs to allow alternatives and then remove them 
(or Steeve's counter)
Steeve
27-Jun-2007
[2042x5]
agree
but  i'ts not very elegant
and i have such rules like this
sniff
so i have to build a pre-parser to transform rules in an elegant 
maner
btiffin
27-Jun-2007
[2047]
I'm still slowly backing out of the room...but I would not be completely 
surprised if another rebol gives you a "tada" solution...but I'd 
bet less money now.  :)
Steeve
27-Jun-2007
[2048]
hihi
Brock
27-Jun-2007
[2049]
well, I'm stumped.  Tried many variations on the theme and couldn't 
get any to work.  Good luck.
Chris
28-Jun-2007
[2050]
Basically you're asking for [all ["A" | "B" | "C"]] -->
ABC
 = true
BAC
 = true
BBC
 = false
ABCB
 = false
btiffin
28-Jun-2007
[2051]
I think Steeve just left...but yep he wants a once and once only 
in any order
Steeve
28-Jun-2007
[2052x3]
i'm here
yeah Chris you got the thing
assuming "A" "B" and "C" could be more complex rules
Chris
28-Jun-2007
[2055]
You may want to check Gabriele's 'compile rules' to see if this has 
been solved.  I have another solution, but needs hashed out a little.
Steeve
28-Jun-2007
[2056]
i know how to build a complex solution but i would prefer a new word 
in the dialect , if other peoples think it's a good improvment
Chris
28-Jun-2007
[2057]
I think so -- it's a common enough pattern...
Gabriele
28-Jun-2007
[2058]
.333