World: r3wp
[Parse] Discussion of PARSE dialect
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Gabriele 25-Dec-2006 [1576x2] | not a bug - you are not skipping the newline, so to "^/" will always match. you are not getting to the end. |
>> rules: [ [ any [ [ end break [ | [ copy value [to newline | to end] (print value) opt skip [ ] [ ] == [ any [ end break | copy value [to newline | to end] (print value) opt skip ] ] >> parse s2 rules str 1 str 2 str 3 == true | |
Joe 25-Dec-2006 [1578x2] | yes, thanks gabriele - happy holidays ! i find the opt skip not very intuitive ! |
wouldn't to newline thru newline be easier to understand than opt skip | |
Volker 25-Dec-2006 [1580] | could be opt newline |
Gabriele 26-Dec-2006 [1581x5] | joe, if you don't care about parse returning true you can just use skip (without opt, which is there for the end case) |
also, if you don't care about your value having the newline in it, you can just replace to newline with thru newline. | |
another possibility (but gives more maineinance problems) is to split the copy rule into two, one for newline and one for end. | |
copy value to newline skip | |
copy value to end | |
Ladislav 27-Dec-2006 [1586x2] | Joe: another option is to use: rules: [ any [ copy value [to newline | to end] (print value) skip ] to end ] |
but, as Gabriele said, that is equivalent to: rules: [ any [ copy value [to newline | to end] (print value) skip ] ] if you ignore the parse result | |
BrianH 27-Dec-2006 [1588x2] | to end skip will always fail. move the skip after the to newline. |
Nevermind, failing isn't a problem here. | |
Ladislav 28-Dec-2006 [1590] | another possibility (but gives more maineinance problems) is to split the copy rule into two, one for newline and one for end. - I am curious whether this isn't actually better when the maintenance is taken into account - suppose e.g. that we want to add yet another alternative... |
Gabriele 28-Dec-2006 [1591x2] | lad, maybe, but if you change the name of the variable to copy to you have then to change it twice in the rule. |
generally, i'd prefer [copy value [rule1 | rule2]] to [copy value rule1 | copy value rule2], however it is not always that easy, so many times you have to do the latter. | |
Anton 28-Dec-2006 [1593] | I agree. |
Maxim 28-Dec-2006 [1594x2] | hi, yesterday I realized I have a 1400 line single parse ruleset which amounts to ~40kb of code ! :-) I was wondering what are your largest Parse rulesets, I'm just curious at how people here are pushing REBOL into extremes. I might also say that parse is wildly efficient in this case, allowing my server to decipher 600 bytes of binary data through all of this huge parse rule within 0.01 - 0.02 seconds (spitting out a nested rebol block tree of rebxml2xml ready data). |
to anyone not yet accustomed to 'PARSE, really do take the time to look it through and use it. | |
Pekr 28-Dec-2006 [1596] | when working so extensively with Parse, you migt try to write down your enhancement/fixes proposal and submit it to R3 team :-) |
Maxim 28-Dec-2006 [1597x4] | The one real limitation I always saw which makes some rules harder to write for nothing is the first-of-any search (to and through) |
and THE MOST PROFOUND limitiation... why the hell is 'NOT within the dialect? | |
50% of the time its easier to match something which is not and then within that choice select something which is. | |
like bounds checking, making sure some items are not within a specific area, etc. | |
Geomol 28-Dec-2006 [1601x3] | My largest Parse rulesets are in NicomDoc. The scripts nicomdoc.r and ndmath.r parse from text to rebxml format. They are 20k and 24k. ndrebxml2html.r parse from NicomDoc rebxml format til html, and that is a 28k script mostly parse rules. I once build a html dialect, and that was 24k. |
And yes, parse is a great tool! | |
The html dialect can be found on the View desktop under REBOL/Public/Sites/Nicom/ | |
Tomc 28-Dec-2006 [1604] | Max complement charset ... can often be used as a sort of NOT |
Maxim 28-Dec-2006 [1605] | true, but that does not match many cases. obviously one can built NOT-A NOT-B and so one.. but man.. that gets tedious, which is not what parse should be. |
Gregg 28-Dec-2006 [1606x2] | I'm pretty sure my biggest parser so far is the one for Qtask's iCal importer: ~75K, ~2,900 lines. It's growing right now, to support recurrence rules and timezones. |
I didn't write the whole thing manually though. I bootstrapped it by writing an ABNF parser, marking up the RFC spec, and generating as much as I could from that. | |
Robert 29-Dec-2006 [1608] | And don't forget to take a look at Gab's compile-rule function. |
Graham 29-Dec-2006 [1609] | what does Gabriele's compile-rule function do ? |
Robert 29-Dec-2006 [1610] | It's an extension to PARSE so you can use things like IF etc. in parse rules. |
Graham 29-Dec-2006 [1611] | Sounds useful. |
Izkata 29-Dec-2006 [1612] | VERY useful... several times I've wanted something like that, but wasn't experienced enough in parse to figure something easy out... |
Pekr 29-Dec-2006 [1613] | why default parse is not extended in native level to support such constructs as IF, to-first, thru first, etc., if many ppl find them usefull? |
Ladislav 29-Dec-2006 [1614] | lad, maybe, but if you change the name of the variable to copy to you have then to change it twice in the rule. - right. That is a general problem of procedural programming style. OTOH, the "opt skip" variant has got another problem - the "opt skip" code is related only to the first alternative, which seems to me like the reason why Joe doesn't like it |
Maxim 29-Dec-2006 [1615] | and where is the compile-rule func? on rebol.org? |
Ladislav 29-Dec-2006 [1616] | have a look at: http://www.compkarori.com/vanilla/display/compile-rules.r my contribution is at: http://www.compkarori.com/vanilla/display/TO%2C+THRU+And+NOT+PARSE+Rules |
Graham 29-Dec-2006 [1617] | oh dear .. vanilla has died on me. I get server error ... |
Ladislav 29-Dec-2006 [1618] | strange, it works for me |
Graham 29-Dec-2006 [1619] | still? |
Ladislav 29-Dec-2006 [1620] | yes |
Graham 29-Dec-2006 [1621x4] | I get server error still. |
now that is bizarre! | |
unless the cookie is corrupting it somehow. | |
must be .. just tried IE and it works fine. | |
Ladislav 29-Dec-2006 [1625] | I am using Firefox 2.0.0.1 |
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