World: r3wp
[Parse] Discussion of PARSE dialect
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BrianH 28-Sep-2009 [4071x3] | Sorry, that would be a different operation. |
Shorter than FROM or GATHER though. | |
Wait, ONE wouldn't work, since you actually get all of the rules, just not in order. | |
Steeve 29-Sep-2009 [4074] | I posted examples to show why a84 is more rebolish. http://www.rebol.net/cgi-bin/r3blog.r?view=0255#comments |
Pekr 29-Sep-2009 [4075x2] | looks good ... |
Steeve - will better parse help with editor? IIRC it was you and Shadwolf, who did it? | |
Steeve 29-Sep-2009 [4077] | A little, but the main drawback i have with parsing in editor is that parse doesn't handle incremental parsing. Because i do parsing line by line to be able to parse only modified lines. So that, i have to rewrite all the rules (describing the document) in an obfuscated way to deal with incremental parsing. |
Pekr 29-Sep-2009 [4078] | BrianH has some plans towards "streamed" parsing. Hopefully it can be done over ports in the future ... |
Steeve 29-Sep-2009 [4079] | Actually, we can simulate streamed/incremental parsing. But we need to transform all the input rules (it can be automatized). I would prefer an inlined behavior of parse for such purpose. It's why i asked to Carl if we could return the rule stack during parsing (i.e. with a special command). |
Pekr 29-Sep-2009 [4080] | What was the answer? I missed your request during yesterday's chat probably ... |
Steeve 29-Sep-2009 [4081] | Request delayed for R3.1 |
Pekr 29-Sep-2009 [4082] | 3.1 - that will be in Spring, so I think that we can wait ... |
Steeve 29-Sep-2009 [4083x3] | it seems |
parse is in mode parse/all by default now, but we can remove the option, a bug ? | |
*we can't | |
BrianH 29-Sep-2009 [4086x2] | /all still affects simple parse (splitting instead of rules). |
With the PARSE changes, this puts us within the range of a parsing model with a reasonably solid theoretical foundation and a lot of experience with parser generators. We could compile PARSE rules into equivalent incremental rules. | |
Steeve 29-Sep-2009 [4088x2] | yep we could start by building a compiler of rules into incremental ones (with rebol i mean) |
i made some tests in the past | |
Steeve 30-Sep-2009 [4090x2] | About STAY, i don't see the interest to continue even if the following rule is not matched . Can someone give an use case ? because when i do this: >> parse [1] [stay skip ?? to end] to: [1] == true or >> parse [ ] [stay skip ?? to end] to: [ ] == true it's like doing: >> parse [ ...] [?? to end] STAY have no purpose to my mind... |
It's just a little annoying, see: >> parse a: "12" [remove copy val skip] print [a val] ==2 none So, the [remove] treats well the [skip], but discard the content of [copy val] Now, see: >> parse a: "12" [remove [copy val skip]] print [a val] == 2 1 The content of [val] is preserved in that case, don't know why here, but not above... | |
Pekr 30-Sep-2009 [4092x2] | I would expect 'val being 1 in both cases ..... |
But maybe reading the "expression" the REBOL way - from left to right, is not correct? | |
Steeve 30-Sep-2009 [4094] | i rather think it's a bug |
Anton 30-Sep-2009 [4095] | Is it that REMOVE takes one argument? |
Pekr 30-Sep-2009 [4096] | Yes, it takes on argument - the rule ... |
Anton 30-Sep-2009 [4097] | (I'm just reading that new blog article about it... Sorry for adding new ignorant question before doing anything to alleviate my ignorance.) |
Pekr 30-Sep-2009 [4098] | sometimes getting reply here on altme is faster than reading corresponding article :-) |
Steeve 30-Sep-2009 [4099] | That's not the problem, SET VAR ot COPY VAR are not rules, they should not be "viewed" by REMOVE |
RobertS 30-Sep-2009 [4100] | I am still guessing at what is intended in R3-a84 but the first looks OK and the second looks like a bug >> parse "abad" [thru "a" stay [to "b"] (print "at b") thru "d"] at b == true >> parse "abad" [stay thru "c" (print "at c") [to "b"] thru "d"] at c == true ; BUT must still be a bug |
Steeve 30-Sep-2009 [4101] | It's not a bug, it's behaving like Carl wanted. The final question is: To do what ? |
Pekr 30-Sep-2009 [4102] | STAY could be a by product by wrongly implemented AND. |
Steeve 30-Sep-2009 [4103] | Yep, a bye bye product |
Pekr 30-Sep-2009 [4104] | express yourself via channels Carl listens to - blog, chat, or even better - CureCode ... :-) |
Steeve 30-Sep-2009 [4105] | I would like to say how the new parse is powerfull and light. For example: I have a block which contains 1, 2, or 3 values I have to insert something between 1 and 2, if there is at least 2 values. and something else between 2 and 3., if there is 3 values. See: parse block [ skip not end insert [ _ ] skip not end insert [ . ] ] Is that not marvelous ? |
Pekr 30-Sep-2009 [4106x2] | this is how it works in A84? |
And we still don't have IF, USE, INTO string! | |
Steeve 30-Sep-2009 [4108] | just think how you would do my example with standard code, it would be more verbose. |
Henrik 30-Sep-2009 [4109] | how does skip not end work? I don't get it. |
Pekr 30-Sep-2009 [4110x3] | skip is skip,no? |
not end means, that the rule is matched as true, if not at end ... | |
it is kind of check | |
Henrik 30-Sep-2009 [4113] | does skip mean, skip 1 element? |
Pekr 30-Sep-2009 [4114x3] | if not at end, insert [.] |
yes, skip is skip 1 by default ... | |
not skip 1, but 1 skip .... | |
Henrik 30-Sep-2009 [4117x2] | ah, forgot that the block is only of max. three values |
BTW, why are we saying END instead of TAIL ? | |
Steeve 30-Sep-2009 [4119] | parse block [ skip ;** skip the first value not end ;** check if the block have a second value (if not, then stop) insert [ _ ] skip ;** insert what is inside [ ] before the second vlue , skip what it has been inserted, and skip one more time to pass the second value. not end ;** check if there is a third value (if not, then stop) insert [ . ] ;** insert [.] before the third value ] |
Henrik 30-Sep-2009 [4120] | I think I get it now, thanks. |
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