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ANTLR Grammar - Error parsing script block

I'm trying to create a grammar in ANTLR, which is depicted bellow.
grammar EPL2;
standard_rule:
'STANDARD' 'RULE' ':'
'FILTER' SCRIPT
'SINK' SCRIPT;
SCRIPT
: '{' SCRIPT_ATOM* '}'
;
fragment SCRIPT_ATOM
: ~[{}]
| '"' ( ~('"') )* '"'
| '//' ~[\r\n]*
| SCRIPT
;
MultiLineComment
: '/*' .*? '*/' -> channel(HIDDEN)
;
SingleLineComment
: '//' ~[\r\n\u2028\u2029]* -> channel(HIDDEN)
;
SPACES
: [ \u000B\t\r\n] -> channel(HIDDEN)
;
When I run the grammar against the following input:
STANDARD RULE:
FILTER { data.get("abc") == "a"; }
SINK { data.get("xyz") > 10 ;}
I get this error:
line 3:36 mismatched input '' expecting 'SINK'
I'm using a IntelliJ plugin to visualize the parse tree and hierarchy. I can see that the second SCRIPT is getting attached to the first as illustrated by the following figure.
When I close the bracket (}) the parser should advance to the sink clause but this isn't happening.
If I add an open or closing bracket to the second String ("{a") the scond
script appears correctly.
I don't know what am I doing wrong, any clues?

antlr grammar for triple quoted string

I am trying to update an ANTLR grammar that follows the following spec
https://github.com/facebook/graphql/pull/327/files
In logical terms its defined as
StringValue ::
- `"` StringCharacter* `"`
- `"""` MultiLineStringCharacter* `"""`
StringCharacter ::
- SourceCharacter but not `"` or \ or LineTerminator
- \u EscapedUnicode
- \ EscapedCharacter
MultiLineStringCharacter ::
- SourceCharacter but not `"""` or `\"""`
- `\"""`
(Not the above is logical - not ANTLR syntax)
I tried the follow in ANTRL 4 but it wont recognize more than 1 character inside a triple quoted string
string : triplequotedstring | StringValue ;
triplequotedstring: '"""' triplequotedstringpart? '"""';
triplequotedstringpart : EscapedTripleQuote* | SourceCharacter*;
EscapedTripleQuote : '\\"""';
SourceCharacter :[\u0009\u000A\u000D\u0020-\uFFFF];
StringValue: '"' (~(["\\\n\r\u2028\u2029])|EscapedChar)* '"';
With these rules it will recognize '"""a"""' but as soon as I add more characters it fails
eg: '"""abc"""' wont parse and the IntelliJ plugin for ANTLR says
line 1:14 extraneous input 'abc' expecting {'"""', '\\"""', SourceCharacter}
How do I do triple quoted strings in ANTLR with '\"""' escaping?

Some of your parer rules should really be lexer rules. And SourceCharacter should probably be a fragment.
Also, instead of EscapedTripleQuote* | SourceCharacter*, you probably want ( EscapedTripleQuote | SourceCharacter )*. The first matches aaa... or bbb..., while you probably meant to match aababbba...
Try something like this instead:
string
: Triplequotedstring
| StringValue
;
Triplequotedstring
: '"""' TriplequotedstringPart*? '"""'
;
StringValue
: '"' ( ~["\\\n\r\u2028\u2029] | EscapedChar )* '"'
;
// Fragments never become a token of their own: they are only used inside other lexer rules
fragment TriplequotedstringPart : EscapedTripleQuote | SourceCharacter;
fragment EscapedTripleQuote : '\\"""';
fragment SourceCharacter :[\u0009\u000A\u000D\u0020-\uFFFF];

Antlr Eclipse IDE White Space not being skipped

I apologize in advance if this question has already been asked, can't seem to find it.
I'm just beginning with Antlr, using the antlr4IDE for Eclipse to create a parser for a small subset of Java. For some reason, unless I explicitly state the presence of a white space in my regex, the parser will throw an error.
My grammar:
grammar Hello;
r :
(Statement ';')+
;
Statement:
DECL | INIT
;
DECL:
'int' ID
;
INIT:
DECL '=' NUMEXPR
;
NUMEXPR :
Number OP Number | Number
;
OP :
'+'
| '-'
| '/'
| '*'
;
WS :
[ \t\r\n\u000C]+ -> skip
;
Number:
[0-9]+
;
ID :
[a-zA-Z]+
;
When trying to parse
int hello = 76;
I receive the error:
Hello::r:1:0: mismatched input 'int' expecting Statement
Hello::r:1:10: token recognition error at: '='
However, when I manually add the token WS into the rules, I receive no error.
Any ideas where I'm going wrong? I'm new to Antlr, so I'm probably making a stupid mistake. Thanks in advance.
EDIT : Here is my parse tree and error log:
Error Log:

Change syntax like this.
grammar Hello;
r : (statement ';')+ ;
statement : decl | init ;
decl : 'int' ID ;
init : decl '=' numexpr ;
numexpr : Number op Number | Number ;
op : '+' | '-' | '/' | '*' ;
WS : [ \t\r\n\u000C]+ -> skip ;
Number : [0-9]+ ;
ID : [a-zA-Z]+ ;

After looking at the documentation on antlr4, it seems like you have to have a specification for all of the character combinations that you expect to see in your file, from start to finish - not just those that you want to handle.
In that regards, it's expected that you would have to explicitly state the whitespace, with something like:
WS : [ \t\r\n]+ -> skip;
That's why the skip command exists:
A 'skip' command tells the lexer to get another token and throw out the current text.
Though note that sometimes this can cause a little trouble such as in this post.

What is the equivalent for epsilon in ANTLR BNF grammar notation?

During taking advantage of ANTLR 3.3, I'm changing the current grammar to support inputs without parenthesis too. Here's the first version of my grammar :
grammar PropLogic;
NOT : '!' ;
OR : '+' ;
AND : '.' ;
IMPLIES : '->' ;
SYMBOLS : ('a'..'z') | '~' ;
OP : '(' ;
CP : ')' ;
prog : formula EOF ;
formula : NOT formula
| OP formula( AND formula CP | OR formula CP | IMPLIES formula CP)
| SYMBOLS ;
WHITESPACE : ( '\t' | ' ' | '\r' | '\n'| '\u000C' )+ { $channel = HIDDEN; } ;
Then I changed it this way to support the appropriate features :
grammar PropLogic;
NOT : '!' ;
OR : '+' ;
AND : '.' ;
IMPLIES : '->' ;
SYMBOL : ('a'..'z') | '~' ;
OP : '(' ;
CP : ')' ;
EM : '' ;
prog : formula EOF ;
formula : OP formula( AND formula CP | OR formula CP | IMPLIES formula CP)
| ( NOT formula | SYMBOL )( AND formula | OR formula | IMPLIES formula | EM ) ;
WHITESPACE : ( '\t' | ' ' | '\r' | '\n'| '\u000C' )+ { $channel = HIDDEN; } ;
But I've been faced with following error :
error<100>: syntax error: invalid char literal: ''
error<100>: syntax error: invalid char literal: ''
Does anybody know that how can I overcome this error?

Your EM token:
EM : '' ;
is invalid: you can't match an empty string in lexer rules.
To match epsilon (nothing), you should do:
rule
: A
| B
| /* epsilon */
;
Of course, the comment /* epsilon */ can safely be removed.
Note that when you do it like that in your current grammar, ANTLR will complain that there can be rules matched using multiple alternatives. This is because your grammar is ambiguous.

I'm not an ANTLR expert, but you might try:
formula : term ((AND | OR | IMPLIES ) term )*;
term : OP formula CP | NOT term | SYMBOL ;
If you want traditional precedence of operators this won't do the trick, but that's another issue.
EDIT: OP raised the ante; he wants precedence too. I'll meet him halfway, since it wasn't part
of the orginal question. I've added precedence to the grammar that makes IMPLIES
the lower precedence than other operators, and leave it to OP to figure out how to do the rest.
formula: disjunction ( IMPLIES disjunction )* ;
disjunction: term (( AND | OR ) term )* ;
term: OP formula CP | NOT term | SYMBOL ;
OP additionally asked, "how to convert (!p or q ) into p -> q". I think he should
have asked this as a separate question. However, I'm already here.
What he needs to do is walk the tree, looking for the pattern he doesn't
like, and change the tree into one he does, and then prettyprint the answer.
It is possible to do all this with ANTLR, which is part of the reason
it is popular.
As a practical matter, procedurally walking the tree and checking the node
types, and splicing out old nodes and splicing in new is doable, but a royal PitA.
Especially if you want to do this for lots of transformations.
A more effective way to do this is to use a
program transformation system, which allows surface syntax patterns to be expressed for matching and replacement. Program transformation systems of course include parsing machinery and more powerful ones let you (and indeed insist) that you define
a grammar up front much as you for ANTLR.
Our DMS Software Reengineering Toolkit is such a program transformation tool, and with a suitably defined grammar for propositions,
the following DMS transformation rule would carry out OP's additional request:
domain proplogic; // tell DMS to use OP's definition of logic as a grammar
rule normalize_implies_from_or( p: term, q: term): formula -> formula
" NOT \p OR \q " -> " \p IMPLIES \q ";
The " ... " is "domain notation", e.g, surface syntax from the proplogic domain, the "\" are meta-escapes,
so "\p" and "\q" represent any arbitrary term from the proplogic grammar. Notice the rule has to reach "across" precedence levels when being applied, as "NOT \p OR \q" isn't a formula and "\p IMPLIES \q" is; DMS takes care of all this (the "formula -> formula" notation is how DMS knows what to do). This rule does a tree-to-tree rewrite. The resulting tree can be prettyprinted by DMS.
You can see a complete example of something very similar, e.g., a grammar for conventional algebra and rewrite rule to simplify algebraic equations.

Split a string on commas not contained within double-quotes with a twist

I asked this question earlier and it was closed because it was a duplicate, which I accept and actually found the answer in the question Java: splitting a comma-separated string but ignoring commas in quotes, so thanks to whoever posted it.
But I've since run into another issue. Apparently what I need to do is use "," as my delimiter when there are zero or an even number of double-quotes, but also ignore any "," contained in brackets.
So the following:
"Thanks,", "in advance,", "for("the", "help")"
Would tokenize as:
Thanks,
in advance,
for("the", "help")
I'm not sure if there's anyway to modify the current regex I'm using to allow for this, but any guidance would be appreciated.
line.split(",(?=([^\"]*\"[^\"]*\")*[^\"]*$)");

Sometimes it is easier to match what you want instead of what you don't want:
String s = "\"Thanks,\", \"in advance,\", \"for(\"the\", \"help\")\"";
String regex = "\"(\\([^)]*\\)|[^\"])*\"";
Pattern p = Pattern.compile(regex);
Matcher m = p.matcher(s);
while(m.find()) {
System.out.println(s.substring(m.start(),m.end()));
}
Output:
"Thanks,"
"in advance,"
"for("the", "help")"
If you also need it to ignore closing brackets inside the quotes sections that are inside the brackets, then you need this:
String regex = "\"(\\((\"[^\"]*\"|[^)])*\\)|[^\"])*\"";
An example of a string which needs this second, more complex version is:
"foo","bar","baz(":-)",":-o")"
Output:
"foo"
"bar"
"baz(":-)",":-o")"
However, I'd advise you to change your data format if at all possible. This would be a lot easier if you used a standard format like XML to store your tokens.

A home-grown parser is easily written.
For example, this ANTLR grammar takes care of your example input without much trouble:
parse
: line*
;
line
: Quoted ( ',' Quoted )* ( '\r'? '\n' | EOF )
;
Quoted
: '"' ( Atom )* '"'
;
fragment
Atom
: Parentheses
| ~( '"' | '\r' | '\n' | '(' | ')' )
;
fragment
Parentheses
: '(' ~( '(' | ')' | '\r' | '\n' )* ')'
;
Space
: ( ' ' | '\t' ) {skip();}
;
and it would be easy to extend this to take escaped quotes or parenthesis into account.
When feeding the parser generated by that grammar to following two lines of input:
"Thanks,", "in advance,", "for("the", "help")"
"and(,some,more)","data , here"
it gets parsed like this:
If you consider to use ANTLR for this, I can post a little HOW-TO to get a parser from that grammar I posted, if you want.