[il-antlr-interest: 33479] Re: [antlr-interest] Have I found an Antlr CSharp3 lexer bug if...
Sam, while trying build my pre-processor with a mixed parser/lexer I ran
across what I think might be a bug. I reduced the repro below. I expected
the program below to accept "/**/ " but instead fails because the lexer
prediction enters PP_SKIPPED_CHARACTERS. That rule has a gated semantic
predicate which is always false. I expected a lexer rule with a gated
semantic predicate which is always false to never be matched. If I comment
out the PP_SKIPPED_CHARACTERS rule then it does match "/**/ ". So the
inclusion of that rule is cause the problem. Let me know if you think this
is a bug and if you can repro.
Thanks,
Chris
grammar Bug;
options {
language=CSharp3;
output=AST;
}
public start
: DELIMITED_COMMENT !EOF
;
PP_SKIPPED_CHARACTERS
: { false }? => ~(F_NEW_LINE_CHARACTER | F_PP_POUND_SIGN)
F_INPUT_CHARACTER*
;
DELIMITED_COMMENT
: { true }? => '/*' .* '*/'
;
WHITESPACE
: F_WHITESPACE {skip();}
;
fragment F_WHITESPACE
: (' ' | '\t' | '\v' | '\f')+
;
fragment F_NEW_LINE_CHARACTER
: '\r'
| '\n'
;
fragment F_PP_POUND_SIGN
: '#'
;
fragment F_INPUT_CHARACTER
: ~F_NEW_LINE_CHARACTER
;
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[il-antlr-interest: 33480] Re: [antlr-interest] Exception when generating tree grammar
Hi Luigi, At first I was thinking, why the heck are you getting an error about a missing StringTemplate file when you have an AST as your output (output=AST). Then I looked more closely at the name of the .st file -- rewriteWildcardLabelRefRoot.st. I think ANTLR sometimes throws these slightly misleading exceptions when you have a syntax error in your grammar. The above StringTemplate file mentions 'wildcard' and 'label' in it, so I guess that the syntax error you have is possibly due to the space between 'single=' (the label) and '.' (the wildcard character). Therefore if you change 'single= .' to 'single=.', that might solve your problem. Stephen List: http://www.antlr.org/mailman/listinfo/antlr-interest Unsubscribe: http://www.antlr.org/mailman/options/antlr-interest/your-email-address -- You received this message because you are subscribed to the Google Groups "il-antlr-interest" group. To post to this group, send email to il-antlr-inter...@googlegroups.com. To unsubscribe from this group, send email to il-antlr-interest+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/il-antlr-interest?hl=en.
[il-antlr-interest: 33481] Re: [antlr-interest] Are the Eclipse ANTLR plugins stable?
By 'stable', do you mean, 'it's not updated very often', or 'there are not many bugs'? I'm guessing you meant the former. Also, what exactly do you mean by an 'ANTLR appliance'? I've used ANTLR IDE, and found it to be very good. I much prefer it to ANTLRWorks. (Although I do still use ANTLRWork's debugging functionality; ANTLR IDE seems to require you to put in breakpoints everywhere in your grammar if you want to be able to (meaningfully) debug your grammar). It seems pretty stable in terms of its 'bug-freeness'. Looking at the website, http://antlrv3ide.sourceforge.net/, it also seems that the plug-in has not been updated for half a year or so. Looks like there were about 5 or so updates over 2010, whilst there's not been any yet this year. Therefore you could infer that it's becoming more stable (either because it does not need updates or because the developer is not actively working on it at the moment). As for ANTLR DT, I don't know anything about it. You might find better (i.e. more official) answers on these things by searching for posts on this mailing list which refer to ANTLR IDE or AntlrDT (using Google). There might be posts by the plug-in writers themselves. Stephen List: http://www.antlr.org/mailman/listinfo/antlr-interest Unsubscribe: http://www.antlr.org/mailman/options/antlr-interest/your-email-address -- You received this message because you are subscribed to the Google Groups "il-antlr-interest" group. To post to this group, send email to il-antlr-inter...@googlegroups.com. To unsubscribe from this group, send email to il-antlr-interest+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/il-antlr-interest?hl=en.
[il-antlr-interest: 33482] Re: [antlr-interest] Exception when generating tree grammar
Hi, unfortunately the removal of the whitespace does not solve it. I get the same error. Cheers, Luigi On 4 Aug 2011, at 14:02, Stephen Tuttlebee wrote: > Hi Luigi, > > At first I was thinking, why the heck are you getting an error about a > missing StringTemplate file when you have an AST as your output > (output=AST). Then I looked more closely at the name of the .st file -- > rewriteWildcardLabelRefRoot.st. I think ANTLR sometimes throws these > slightly misleading exceptions when you have a syntax error in your > grammar. > > The above StringTemplate file mentions 'wildcard' and 'label' in it, so > I guess that the syntax error you have is possibly due to the space > between 'single=' (the label) and '.' (the wildcard character). > Therefore if you change 'single= .' to 'single=.', that might solve your > problem. > > Stephen > > > > List: http://www.antlr.org/mailman/listinfo/antlr-interest > Unsubscribe: > http://www.antlr.org/mailman/options/antlr-interest/your-email-address List: http://www.antlr.org/mailman/listinfo/antlr-interest Unsubscribe: http://www.antlr.org/mailman/options/antlr-interest/your-email-address -- You received this message because you are subscribed to the Google Groups "il-antlr-interest" group. To post to this group, send email to il-antlr-inter...@googlegroups.com. To unsubscribe from this group, send email to il-antlr-interest+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/il-antlr-interest?hl=en.
[il-antlr-interest: 33483] Re: [antlr-interest] Have I found an Antlr CSharp3 lexer bug if...
Hi Chris,
I'm using the released version 3.4.0 of the ANTLR CSharp3 target. I
copy/pasted the grammar below (aside from renaming it to Preprocessor) and
it passed the following unit test.
[TestMethod]
public void TestEmptyComment()
{
string inputText = "/**/";
var input = new ANTLRStringStream(inputText);
var lexer = new PreprocessorLexer(input);
var tokenStream = new CommonTokenStream(lexer);
tokenStream.Fill();
List tokens = tokenStream.GetTokens();
Assert.AreEqual(2, tokens.Count);
Assert.AreEqual(PreprocessorLexer.DELIMITED_COMMENT, tokens[0].Type);
Assert.AreEqual(inputText, tokens[0].Text);
Assert.AreEqual(PreprocessorLexer.EOF, tokens[1].Type);
}
Sam
From: chris king [mailto:kingce...@gmail.com]
Sent: Thursday, August 04, 2011 3:48 AM
To: Sam Harwell; antlr-interest@antlr.org
Subject: Re: Have I found an Antlr CSharp3 lexer bug if...
Sam, while trying build my pre-processor with a mixed parser/lexer I ran
across what I think might be a bug. I reduced the repro below. I expected
the program below to accept "/**/ " but instead fails because the lexer
prediction enters PP_SKIPPED_CHARACTERS. That rule has a gated semantic
predicate which is always false. I expected a lexer rule with a gated
semantic predicate which is always false to never be matched. If I comment
out the PP_SKIPPED_CHARACTERS rule then it does match "/**/ ". So the
inclusion of that rule is cause the problem. Let me know if you think this
is a bug and if you can repro.
Thanks,
Chris
grammar Bug;
options {
language=CSharp3;
output=AST;
}
public start
: DELIMITED_COMMENT !EOF
;
PP_SKIPPED_CHARACTERS
: { false }? => ~(F_NEW_LINE_CHARACTER | F_PP_POUND_SIGN)
F_INPUT_CHARACTER*
;
DELIMITED_COMMENT
: { true }? => '/*' .* '*/'
;
WHITESPACE
: F_WHITESPACE {skip();}
;
fragment F_WHITESPACE
: (' ' | '\t' | '\v' | '\f')+
;
fragment F_NEW_LINE_CHARACTER
: '\r'
| '\n'
;
fragment F_PP_POUND_SIGN
: '#'
;
fragment F_INPUT_CHARACTER
: ~F_NEW_LINE_CHARACTER
;
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[il-antlr-interest: 33484] Re: [antlr-interest] Exception when generating tree grammar
Well, to refresh my memory on this term rewriting stuff you're doing, I looked at Terence Parr's Language Implementation Patterns book which has a section about this (if you have the book, it's p138 in the pdf edition). I think then it might be your tree construction rewrite rules that are syntactically incorrect. Maybe it should be: -> $single rather than: -> ^($single) Hope it works this time... Stephen List: http://www.antlr.org/mailman/listinfo/antlr-interest Unsubscribe: http://www.antlr.org/mailman/options/antlr-interest/your-email-address -- You received this message because you are subscribed to the Google Groups "il-antlr-interest" group. To post to this group, send email to il-antlr-inter...@googlegroups.com. To unsubscribe from this group, send email to il-antlr-interest+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/il-antlr-interest?hl=en.
[il-antlr-interest: 33485] Re: [antlr-interest] Exception when generating tree grammar
It works, Thanks, Luigi On 4 Aug 2011, at 15:41, Stephen Tuttlebee wrote: > Well, to refresh my memory on this term rewriting stuff you're doing, I > looked at Terence Parr's Language Implementation Patterns book which has > a section about this (if you have the book, it's p138 in the pdf edition). > > I think then it might be your tree construction rewrite rules that are > syntactically incorrect. > Maybe it should be: > -> $single > rather than: > -> ^($single) > > Hope it works this time... > Stephen > > > List: http://www.antlr.org/mailman/listinfo/antlr-interest > Unsubscribe: > http://www.antlr.org/mailman/options/antlr-interest/your-email-address List: http://www.antlr.org/mailman/listinfo/antlr-interest Unsubscribe: http://www.antlr.org/mailman/options/antlr-interest/your-email-address -- You received this message because you are subscribed to the Google Groups "il-antlr-interest" group. To post to this group, send email to il-antlr-inter...@googlegroups.com. To unsubscribe from this group, send email to il-antlr-interest+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/il-antlr-interest?hl=en.
[il-antlr-interest: 33490] Re: [antlr-interest] Have I found an Antlr CSharp3 lexer bug if...
I should have called out the space after the comment. That's what caused the
problem. "/**/ ". So the input string has 5 characters.
Thanks,
Chris
On Aug 4, 2011, at 7:04 AM, "Sam Harwell" wrote:
> Hi Chris,
>
>
>
> I’m using the released version 3.4.0 of the ANTLR CSharp3 target. I
> copy/pasted the grammar below (aside from renaming it to Preprocessor) and it
> passed the following unit test.
>
>
>
> [TestMethod]
>
> public void TestEmptyComment()
>
> {
>
> string inputText = "/**/";
>
> var input = new ANTLRStringStream(inputText);
>
> var lexer = new PreprocessorLexer(input);
>
> var tokenStream = new CommonTokenStream(lexer);
>
> tokenStream.Fill();
>
>
>
> List tokens = tokenStream.GetTokens();
>
> Assert.AreEqual(2, tokens.Count);
>
> Assert.AreEqual(PreprocessorLexer.DELIMITED_COMMENT, tokens[0].Type);
>
> Assert.AreEqual(inputText, tokens[0].Text);
>
> Assert.AreEqual(PreprocessorLexer.EOF, tokens[1].Type);
>
> }
>
>
>
> Sam
>
>
>
> From: chris king [mailto:kingce...@gmail.com]
> Sent: Thursday, August 04, 2011 3:48 AM
> To: Sam Harwell; antlr-interest@antlr.org
> Subject: Re: Have I found an Antlr CSharp3 lexer bug if...
>
>
>
> Sam, while trying build my pre-processor with a mixed parser/lexer I ran
> across what I think might be a bug. I reduced the repro below. I expected the
> program below to accept "/**/ " but instead fails because the lexer
> prediction enters PP_SKIPPED_CHARACTERS. That rule has a gated semantic
> predicate which is always false. I expected a lexer rule with a gated
> semantic predicate which is always false to never be matched. If I comment
> out the PP_SKIPPED_CHARACTERS rule then it does match "/**/ ". So the
> inclusion of that rule is cause the problem. Let me know if you think this is
> a bug and if you can repro.
>
>
>
> Thanks,
> Chris
>
>
>
> grammar Bug;
>
>
>
> options {
>
>language=CSharp3;
>
>output=AST;
>
> }
>
>
>
> public start
>
> : DELIMITED_COMMENT !EOF
>
> ;
>
>
>
> PP_SKIPPED_CHARACTERS
>
> : { false }? => ~(F_NEW_LINE_CHARACTER | F_PP_POUND_SIGN) F_INPUT_CHARACTER*
>
> ;
>
>
>
> DELIMITED_COMMENT
>
> : { true }? => '/*' .* '*/'
>
> ;
>
>
>
> WHITESPACE
>
> : F_WHITESPACE {skip();}
>
> ;
>
>
>
> fragment F_WHITESPACE
>
> : (' ' | '\t' | '\v' | '\f')+
>
> ;
>
>
>
> fragment F_NEW_LINE_CHARACTER
>
> : '\r'
>
> | '\n'
>
> ;
>
>
>
> fragment F_PP_POUND_SIGN
>
> : '#'
>
> ;
>
>
>
> fragment F_INPUT_CHARACTER
>
> : ~F_NEW_LINE_CHARACTER
>
> ;
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[il-antlr-interest: 33491] Re: [antlr-interest] Are the Eclipse ANTLR plugins stable?
Stephen, Thanks for the response. An appliance is a application that can run as a virtual machine. I am making one for people just learning ANTLR but that have trouble installing the various components, or possibly in classroom use. Think VMware or Virtual Box. Since posing the question I checked the licenses and only ANTLR IDE can be used. One interesting thing is that Eclipse is up to version 3.7 (Indigo) but as you note ANTLR IDE has not been updated. Its latest version is for Eclipse 3.6 (Helios). I have never used it, but your notes will be of value when I document using it. Thanks Eric List: http://www.antlr.org/mailman/listinfo/antlr-interest Unsubscribe: http://www.antlr.org/mailman/options/antlr-interest/your-email-address -- You received this message because you are subscribed to the Google Groups "il-antlr-interest" group. To post to this group, send email to il-antlr-inter...@googlegroups.com. To unsubscribe from this group, send email to il-antlr-interest+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/il-antlr-interest?hl=en.
[il-antlr-interest: 33492] [antlr-interest] Line oriented parsing with Unix files on Windows machine
I have a line-oriented grammar that uses the following rule to define an
end of line:
EOL : ('\r' | '\n')+;
My grammar parses input files fine when they are in windows format
(lines end with '\r\n'), however the parser doesn't work when the input
files are in unix format (lines end with '\n' only). It seems to ignore
the new line character and attach it to the subsequent rule. Is there
something I need to do the process these files correctly? Any ideas?
Thanks.
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[il-antlr-interest: 33493] [antlr-interest] Looking for an example of tree walking using push/pop
Hello- I'm working on a grammar that has nested subtrees. I am successfully parsing the input to create the AST, but am having trouble navigating the tree to build the structure my Java program needs. The output is a HashMap. When it's not a leaf node, the Object in the map will be a HashMap. Can you point me to some examples of more complicated tree walkers than the ones I've been able to find? I have been though the video tutorial as well. Thanks in advance. List: http://www.antlr.org/mailman/listinfo/antlr-interest Unsubscribe: http://www.antlr.org/mailman/options/antlr-interest/your-email-address -- You received this message because you are subscribed to the Google Groups "il-antlr-interest" group. To post to this group, send email to il-antlr-inter...@googlegroups.com. To unsubscribe from this group, send email to il-antlr-interest+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/il-antlr-interest?hl=en.
[il-antlr-interest: 33494] Re: [antlr-interest] Looking for an example of tree walking using push/pop
This has an example of how to go down the AST and then back up. http://www.antlr.org/wiki/display/ANTLR3/Tree+pattern+matching This is a concrete example of the method on the wiki. I used it in my experiment about learning how to make an interpreter. EveCore calls the downup method. The .g file is the grammar, of course. https://github.com/ProjectMoon/eve2/blob/master/src/eve/core/EveCore.java#L227 https://github.com/ProjectMoon/eve2/blob/master/src/eve/core/ASTParser.g On Thu, Aug 4, 2011 at 3:48 PM, wrote: > Hello- I'm working on a grammar that has nested subtrees. I am successfully > parsing the input to create the AST, but am having trouble navigating the > tree to build the structure my Java program needs. The output is a > HashMap. When it's not a leaf node, the Object in the map > will be a HashMap. Can you point me to some examples of more > complicated tree walkers than the ones I've been able to find? I have been > though the video tutorial as well. Thanks in advance. > > > > List: http://www.antlr.org/mailman/listinfo/antlr-interest > Unsubscribe: > http://www.antlr.org/mailman/options/antlr-interest/your-email-address > List: http://www.antlr.org/mailman/listinfo/antlr-interest Unsubscribe: http://www.antlr.org/mailman/options/antlr-interest/your-email-address -- You received this message because you are subscribed to the Google Groups "il-antlr-interest" group. To post to this group, send email to il-antlr-inter...@googlegroups.com. To unsubscribe from this group, send email to il-antlr-interest+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/il-antlr-interest?hl=en.
[il-antlr-interest: 33495] Re: [antlr-interest] Line oriented parsing with Unix files on Windows machine
Hi Todd,
Well, `EOL : ('\r' | '\n')+;` matches a single `\n`. So my guess is that
some other rule in your grammar matches a `\n` as well. Can you post a
complete (small) grammar that shows the problem you're having?
Regards,
Bart.
On Thu, Aug 4, 2011 at 8:37 PM, Stevenson, Todd (GE Healthcare) <
todd.t.steven...@ge.com> wrote:
> I have a line-oriented grammar that uses the following rule to define an
> end of line:
>
>
>
> EOL : ('\r' | '\n')+;
>
>
>
> My grammar parses input files fine when they are in windows format
> (lines end with '\r\n'), however the parser doesn't work when the input
> files are in unix format (lines end with '\n' only). It seems to ignore
> the new line character and attach it to the subsequent rule. Is there
> something I need to do the process these files correctly? Any ideas?
>
>
>
> Thanks.
>
>
>
>
>
>
>
>
>
>
> List: http://www.antlr.org/mailman/listinfo/antlr-interest
> Unsubscribe:
> http://www.antlr.org/mailman/options/antlr-interest/your-email-address
>
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[il-antlr-interest: 33497] Re: [antlr-interest] To Sam Harwell
Hi Chris, In build 3.4.1.9004 that I released today, I switched all the projects to using $(ProjectDir) with relative paths. http://www.antlr.org/wiki/display/ANTLR3/Antlr3CSharpReleases Sam -Original Message- From: antlr-interest-boun...@antlr.org [mailto:antlr-interest-boun...@antlr.org] On Behalf Of chris king Sent: Monday, July 25, 2011 6:39 PM To: antlr-interest@antlr.org Subject: [antlr-interest] To Sam Harwell Sam, hey, hope this finds you. Very small suggestion follows :). In Antlr3.StringTemplate.csproj could you use $(MSBuildProjectDirectory)\..\bin\Bootstrap to reference the bootstrap directory? Originally it used the solutionDir and that prevented me from including a subset of the projects in my project (so I could simply reference them and have all the debugging, pdb, source, etc just work). Thanks, Chris List: http://www.antlr.org/mailman/listinfo/antlr-interest Unsubscribe: http://www.antlr.org/mailman/options/antlr-interest/your-email-address List: http://www.antlr.org/mailman/listinfo/antlr-interest Unsubscribe: http://www.antlr.org/mailman/options/antlr-interest/your-email-address -- You received this message because you are subscribed to the Google Groups "il-antlr-interest" group. To post to this group, send email to il-antlr-inter...@googlegroups.com. To unsubscribe from this group, send email to il-antlr-interest+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/il-antlr-interest?hl=en.
[il-antlr-interest: 33498] Re: [antlr-interest] To Sam Harwell
Awesome! I'll give it try. Did you see my follow up email that the parse string is 5 characters (there is a trailing space)? "/**/ " And again, love the tool chain. I only really started to get traction on my project after I installed it. It's working great. Thanks, Chris On Thu, Aug 4, 2011 at 4:34 PM, Sam Harwell wrote: > Hi Chris, > > In build 3.4.1.9004 that I released today, I switched all the projects to > using $(ProjectDir) with relative paths. > > http://www.antlr.org/wiki/display/ANTLR3/Antlr3CSharpReleases > > Sam > > -Original Message- > From: antlr-interest-boun...@antlr.org > [mailto:antlr-interest-boun...@antlr.org] On Behalf Of chris king > Sent: Monday, July 25, 2011 6:39 PM > To: antlr-interest@antlr.org > Subject: [antlr-interest] To Sam Harwell > > Sam, hey, hope this finds you. Very small suggestion follows :). In > Antlr3.StringTemplate.csproj could you use > > > > $(MSBuildProjectDirectory)\..\bin\Bootstrap askPath> > > to reference the bootstrap directory? Originally it used the solutionDir > and > that prevented me from including a subset of the projects in my project (so > I could simply reference them and have all the debugging, pdb, source, etc > just work). > > Thanks, > Chris > > List: http://www.antlr.org/mailman/listinfo/antlr-interest > Unsubscribe: > http://www.antlr.org/mailman/options/antlr-interest/your-email-address > > List: http://www.antlr.org/mailman/listinfo/antlr-interest Unsubscribe: http://www.antlr.org/mailman/options/antlr-interest/your-email-address -- You received this message because you are subscribed to the Google Groups "il-antlr-interest" group. To post to this group, send email to il-antlr-inter...@googlegroups.com. To unsubscribe from this group, send email to il-antlr-interest+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/il-antlr-interest?hl=en.
[il-antlr-interest: 33499] [antlr-interest] Another (hopefully easy) newby question
I have created a parser/lexer. When I run it as a standard parser (no ASTs),
it runs fine. I've verified with the debugger, that it generates a reasonable
tree.
But, I want to run it to generate ASTs. So, I modified the code to do that
(using ^ to promote operators and ! to eliminate some things). I believe that
is working just fine as well.
So, here's the problem. My test harness looks like:
String filename = ".\\somefile.txt";
CharStream stream = new ANTLRFileStream(filename);
MyFilterLexer lexer = new MyFilterLexer(stream);
TokenStream tokenStream = new CommonTokenStream(lexer);
MyFilterParser parser = new MyFilterParser(tokenStream);
filter_return f = parser.filter();
System.out.println(f.getTree().toString());
I want the print out to display the AST version of the parsed data. I know it
exists (at least mostly) because I can modify the top level parser item in my
combined grammer as follows:
filter:
FQ '='^ filter_expr EOF!
{
if ($filter_expr.tree != null)
System.out.println($filter_expr.tree.toStringTree());
else
System.out.println("must be null");
}
;
This compiles and does display (almost all) the ASTs as I would expect. Note
that it is referencing the "filter_expr" and not the "filter". It does not
display the "(= FQ" but the rest of my ASTs appear to be properly parsed and
ordered. If I change to use $filter instead, then I get the "must be null"
message.
Isn't there a way to display the string of ASTs from the filter_return object?
Scott Stanchfield's video would say you could do
"System.out.println(f.tree.getStringTree());", but that doesn't compile with
Antlr 3.4.
If I run the harness as I have it above, it simply prints "=".
What am I missing?
Thanks
Scott
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[il-antlr-interest: 33500] Re: [antlr-interest] Another (hopefully easy) newby question
On Fri, 2011-08-05 at 01:15 +, Scott Smith wrote:
> I have created a parser/lexer. When I run it as a standard parser (no ASTs),
> it runs fine. I've verified with the debugger, that it generates a
> reasonable tree.
>
> But, I want to run it to generate ASTs. So, I modified the code to do that
> (using ^ to promote operators and ! to eliminate some things). I believe that
> is working just fine as well.
>
> So, here's the problem. My test harness looks like:
>
> String filename = ".\\somefile.txt";
> CharStream stream = new ANTLRFileStream(filename);
> MyFilterLexer lexer = new MyFilterLexer(stream);
> TokenStream tokenStream = new CommonTokenStream(lexer);
> MyFilterParser parser = new MyFilterParser(tokenStream);
> filter_return f = parser.filter();
> System.out.println(f.getTree().toString());
>
> I want the print out to display the AST version of the parsed data. I know it
> exists (at least mostly) because I can modify the top level parser item in my
> combined grammer as follows:
>
> filter:
> FQ '='^ filter_expr EOF!
> {
> if ($filter_expr.tree != null)
> System.out.println($filter_expr.tree.toStringTree());
> else
> System.out.println("must be null");
> }
> ;
>
> This compiles and does display (almost all) the ASTs as I would expect. Note
> that
> it is referencing the "filter_expr" and not the "filter". It does not
> display the
> "(= FQ" but the rest of my ASTs appear to be properly parsed and ordered. If
> I
> change to use $filter instead, then I get the "must be null" message.
when using the ^ and/or ! meta-operators, the result tree is not created
until the end of the rule.
technically your printing action is not at the end of the rule because
stuff could appear after that action.
put your print code in the rule's @after{...} section and a reference to
the rulename.tree will not be null.
>
> Isn't there a way to display the string of ASTs from the filter_return
> object?
> Scott Stanchfield's video would say you could do
> "System.out.println(f.tree.getStringTree());",
> but that doesn't compile with Antlr 3.4.
>
> If I run the harness as I have it above, it simply prints "=".
>
the toString() method of CommonTree does not recurse into the tree's
children (if any). so that is why you see just the root node printed by
your driver.
need to use the toStringTree() method in your driver in order to get the
entire tree printed --- just as you did in your rule's printing action.
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