I need to get the pieces of text out of text)). Very simple example actually, but gives me quite some pain.
Here is the sample text, it is an email template:
{!Account.Name}
Hi hi there {!Account.Id + 'cool'}.
Very interesting stuff - {!Contact.Description}
Now we get {!Contact.Description + Contact.Email__c}
So I need all the occurances of text like Account.Name, but only those which are within opening "{!" and closing "}" tags.
What is the simplest/starting approach to do it? Note that in case of the last line, I need to get the two occurances, Contact.Description and Contact.Email__c.
Thanks a lot for any help!
I would just do a plain text search for {...} blocks and parse their content with a simple expression parser. Don't try to come up with a parser that gets all the text and must be prepared to deal with any rubbish that can come in outside of the blocks (which could ultimatively lead to security problems).
Related
I've got a file format that looks a little like this:
blockA {
uniqueName42 -> uniqueName aWord1 anotherWord "Some text"
anotherUniqueName -> uniqueName23 aWord2
blockB {
thing -> anotherThing
}
}
Lots more blocks with arbitrary nesting levels.
The lines with the arrow in them define relationships between two things. Each relationship has some optional metadata (multi-word quoted or single word unquoted).
The challenge I'm having is that because the there can be an arbitrary number of metadata items in a relationship my parser is treating anotherUniqueName as a metadata item from the first relationship rather than the start of the second relationship.
You can see this in the image below. The parser is only recognising one relationshipDeclaration when a second should start with StringLiteral: anotherUniqueName
The parser looks a bit like this:
block
: BLOCK LBRACE relationshipDeclaration* RBRACE
;
relationshipDeclaration
: StringLiteral? ARROW StringLiteral StringLiteral*
;
I'm hoping to avoid lexical modes because the fact that these relationships can appear almost anywhere in the file will leave me up to my eyes in NL+ :-(
Would appreciate any ideas on what options I have. Is there a way to look ahead, spot the '->', for example?
Thanks a million.
Your example certainly looks like the NL is what signals the end of a relationshipDeclaration.
If that's the case, then you'll need NLs to be tokens available to your parse rules so the parser can know recognize the end.
As you've alluded to, you could potentially use -> to trigger a different Lexer Mode and generate different tokens for content between the -> and the NL and then use those tokens in your parse rule for relationshipDeclaration.
If it's as simple as your snippet indicates, then just capturing RD_StringLiteral tokens in that lexical mode, would probably be easier to deal with than handling all the places you might need to allow for NL. This would be pretty simple as Lexer modes go.
(BTW you can use x+ to get the same effect as x x*)
relationshipDeclaration
: StringLiteral? ARROW RD_StringLiteral+
;
I don't think there's a third option for dealing with this.
I'm trying to make a "very simple" syntax highlight for "cottle" (which is a script language used in a text-to-speech app dedicated to Elite:Dangerous).
All i want (at least at the beginning) is to have three different colours: Comments, "non-strings", and strings.
I started trying with the ST3 wiki, youtube tutorials, questions here.... but i can't sort out how to do it, 'cause the way the language work.
I'll try to show you an example
{ everything_between_a_pair_of_brackets_is_code }
everything outside all pairs of bracket is a string {_ and this is a comment. It begins with "_" and ends at the closing bracket }
{ This_is_code("but this is a string")
This_is_still_code("this is also a string {but_this_is_code(\"and a string\")} and this the end of the string")
}
My problem is how to define this kind of "nidification" in my cottle.sublime-syntax file. I managed to get the comment, but only the first one.
- EDIT -
This is a real script:
{event.item}
{if event.repairedfully:
fully repaired
|else:
partially repaired
{Occasionally(2,
cat(
OneOf("to ", "at "),
Humanise(event.health * 100),
" percent functionality"
)
)}
}
{Occasionally(2,
cat(OneOf(", ", "and is"), " ready for re-activation")
)}.
The output of this script could be "Engine module fully repaired." or "Engine module partially repaired, and is ready for re-activation."
Please note the last dot of the phrase, which in the code is after the last bracket.
This is another sample, with strings passed to functions inside other strings:
{OneOf("{ShipName()} has", "")}
{OneOf("left supercruise", "{OneOf(\"entered\", \"returned to\", \"dropped to\")} normal space")}
My question is:
how sublime-syntax files handle this kind of nidification?
Looking at the overview of the templating language over at https://cottle.readthedocs.io/en/stable/page/01-overview.html, it seems to be an easy syntax for which to write a .sublime-syntax for, but given the utter lack of resources for knowing how syntax files works in ST, I can understand it can be sometimes difficult to start or even understand.
So, I took the liberty of creating a starter syntax definition (the result of an hour & a half of boredom on a Saturday evening), which you can take and work upon. Note that I have not used the language and as such made it by just reading the docs and looking over code snippets.
You can find a gist for it here (https://gist.github.com/Ultra-Instinct-05/96fa99e1aaeb32b12d1e62109d61fcc2)
Here is a screenshot showing it in the color scheme I use (which follows the official scope naming guidelines).
It still lacks support for user defined functions (as I came to know from the docs) (and probably a few other things), but maybe that's something you can add to it !
Note that to use it, save the file as Cottle.sublime-syntax in your User package. Right now files having a .cottle extension are highlighted (because I don't know how you create a cottle file).
The syntax definition doesn't use any new feature added in ST4, so it should work the same in both ST3 & ST4.
I am trying to parse a config, which would translate to a structured form. This new form requires that comments within the original config be preserved. The parsing tool is PLY. I am running into an issue with my current approach which I will describe in detail below, with links to code as well. The config file is going to look contain multiple config blocks, each of which is going to be of the following format
<optional comments>
start_of_line request_stmts(one or more)
indent reply_stmts (zero or more)
include_stmts (type 3)(zero or more)
An example config file looks like this.
While I am able to partially parse the config file with the grammar below, I fail to accomodate comments which would exist within the block.
For example, a block like this raises syntax errors, and any comments in a block of config fail to parse.
<optional comments>
start_of_line request_stmts(type 1)(one or more)
indent reply_stmts (type 2)(one or more)
<comments>
include_stmts (type 3)(one or more)(optional)
The parser.out mentions one shift/reduce conflict which I think arises because once the reply_stmts are parsed, a comments section which follows could mark start of a new block or comments within the subblock. Current grammar parsing result for the example file
[['# test comment ', '# more of this', '# does this make sense'], 'DEFAULT', [['x', '=',
'y']], [['y', '=', '1']], ['# Transmode', '# maybe something else', '# comment'],
'/random/location/test.user']
As you might notice, the second config block complete misses the username, request_stmt, reply_stmt sections.
What I have tried
I have tried moving the comments section around in the grammar, by specifying it before specific blocks or in the statement grammar. In the code link pasted above, the comments section has been specified in the overall statement grammar. Both of these approaches fail to parse comments within a config block.
username : comments username
| username
include_stmt : comments includes
| includes
I have two main questions:
Is there a mistake I am making in the implementation/understanding of LR parsing, solving which I could achieve what I want to ?
Is there a better way to achieve the same goal than my current approach ? (PLY-fu, different parser, different grammar)
P.S Wasn't able to include the actual code in the question, mentioned in the comments
You are correct that the problem is that when the parser sees a comment, it cannot know whether the comment belongs to the same section or whether the previous section is finished. In the former case, the parser needs to shift the comment, while in the latter case it needs to reduce the configuration section.
Since there could be any number of comments, the necessary lookahead could be arbitrarily large, in which case LR parsing wouldn't be possible. But a simple trick can reduce the lookahead to two tokens: just combine consecutive comments into a single token.
Any LR(k) grammar has an equivalent LR(1) grammar. In effect, the LR(1) grammars works by delaying all decisions for k-1 tokens, accumulating these tokens into the parser state. That's a massive increase in grammar size, but it's usually possible to achieve the same effect in other ways, and that's certainly the case here.
The basic idea is that any comment is (temporarily) accumulated into a list of comments. When a non-comment token is encountered, this temporary list is attached to that token.
This can be done either in the lexical scanner or in the parser actions, depending on your inclinations.
Before attempting all that, you should make sure that retaining comments is really useful to your application. Comments are normally not relevant to the semantics of a program (or configuration file), and it would certainly be much simpler for the lexer to just drop comments into the bit-bucket. If your application will end up reformatting the input, then it will have to retain comments. But if it only needs to extract information from the configuration, putting a lot of effort into handling comments is hard to justify.
I'm trying to write an antlr4 parser rule that can match the content between some arbitrary string values that are same. So far I couldn't find a method to do it.
For example, in the below input, I need a rule to extract Hello and Bye. I'm not interested in extracting xyz though.
TEXT Hello TEXT
TEXT1 Bye TEXT1
TEXT5 xyz TEXT8
As it is very much similar to an XML element grammar, I tried an example for XML Parser given in ANTLR4 XML Grammar, but it parses an input like <ABC> ... </XYZ> without error which is not what I wanted.
I also tried using semantic predicates without much success.
Could anyone please help with a hint on how to match content that is embedded between same strings?
Thank you!
Satheesh
Not sure how this works out performance wise, because of many many checks the parser has to do, but you could try something like:
token:
start = IDENTIFIER WORD* end = IDENTIFIER { start == end }?
;
The part between the curly braces is a validating semantic predicate. The lexer tokens are self-explanatory, I believe.
The more I think about it, it might be better you just tokenize the input and write an owner parser that processes the input and acts accordingly. Depends of course on the complexity of the syntax.
How does a lexer solve this ambiguity?
/*/*/
How is it that it doesn't just say, oh yeah, that's the begining of a multi-line comment, followed by another multi-line comment.
Wouldn't a greedy lexer just return the following tokens?
/*
/*
/
I'm in the midst of writing a shift-reduce parser for CSS and yet this simple comment thing is in my way. You can read this question if you wan't some more background information.
UPDATE
Sorry for leaving this out in the first place. I'm planning to add extensions to the CSS language in this form /* # func ( args, ... ) */ but I don't want to confuse an editor which understands CSS but not this extension comment of mine. That's why the lexer just can't ignore comments.
One way to do it is for the lexer to enter a different internal state on encountering the first /*. For example, flex calls these "start conditions" (matching C-style comments is one of the examples on that page).
The simplest way would probably be to lex the comment as one single token - that is, don't emit a "START COMMENT" token, but instead continue reading in input until you can emit a "COMMENT BLOCK" token that includes the entire /*(anything)*/ bit.
Since comments are not relevant to the actual parsing of executable code, it's fine for them to basically be stripped out by the lexer (or at least, clumped into a single token). You don't care about token matches within a comment.
In most languages, this is not ambiguous: the first slash and asterix are consumed to produce the "start of multi-line comment" token. It is followed by a slash which is plain "content" within the comment and finally the last two characters are the "end of multi-line comment" token.
Since the first 2 characters are consumed, the first asterix cannot also be used to produce an end of comment token. I just noted that it could produce a second "start of comment" token... oops, that could be a problem, depending on the amount of context is available for the parser.
I speak here of tokens, assuming a parser-level handling of the comments. But the same applies to a lexer, whereby the underlying rule is to start with '/*' and then not stop till '*/' is found. Effectively, a lexer-level handling of the whole comment wouldn't be confused by the second "start of comment".
Since CSS does not support nested comments, your example would typically parse into a single token, COMMENT.
That is, the lexer would see /* as a start-comment marker and then consume everything up to and including a */ sequence.
Use the regexp's algorithm, search from the beginning of the string working way back to the current location.
if (chars[currentLocation] == '/' and chars[currentLocation - 1] == '*') {
for (int i = currentLocation - 2; i >= 0; i --) {
if (chars[i] == '/' && chars[i + 1] == '*') {
// .......
}
}
}
It's like applying the regexp /\*([^\*]|\*[^\/])\*/ greedy and bottom-up.
One way to solve this would be to have your lexer return:
/
*
/
*
/
And have your parser deal with it from there. That's what I'd probably do for most programming languages, as the /'s and *'s can also be used for multiplication and other such things, which are all too complicated for the lexer to worry about. The lexer should really just be returning elementary symbols.
If what the token is starts to depend too much on context, what you're looking for may very well be a simpler token.
That being said, CSS is not a programming language so /'s and *'s can't be overloaded. Really afaik they can't be used for anything else other than comments. So I'd be very tempted to just pass the whole thing as a comment token unless you have a good reason not to: /\*.*\*/