[il-antlr-interest: 31406] [antlr-interest] semantic predicates
Hi,
I'm new to ANTLR and have a problem with the following toy grammar,
which uses semantic predicates to disambiguate operator precedences. The
idea is to support dynamic prolog style operator declarations, where
lower precedence binds tighter. On the input 3*3+3, the epsilon
production of the rule rterm is not choosen, but instead I get a
NoViableAltException, which I do not understand. I'm aware that I could
also express the precedences in the productions, but this is not what I
want because the overall goal later is to support dynamic operators. Can
you please help?
Thanks.
grammar PTermParser;
options {
output=AST;
}
@members {
public static void main(String[] args) throws Exception {
PTermParserLexer lex = new PTermParserLexer(new
ANTLRFileStream(args[0]));
CommonTokenStream tokens = new CommonTokenStream(lex);
PTermParserParser parser = new PTermParserParser(tokens);
try {
parser.term(1200);
} catch (RecognitionException e) {
e.printStackTrace();
}
}
}
WHITESPACE: (' ' | '\t')+ { $channel = HIDDEN; };
NEWLINE: ('\r'? '\n')+ { $channel = HIDDEN;} ;
IDENTIFIER :LETTER (LETTER | DIGIT | '_')*;
NUMBER :DIGIT+;
OPERATORSEQ : SPECIALCHAR+;
fragment LETTER
: 'a'..'z'
| 'A'..'Z'
;
fragment DIGIT:'0' .. '9';
fragment SPECIALCHAR :'+' | '-' | '*' | '/';
start
@init{
System.out.println(start);
}
: term[1200];
term[int prec]
@init{
System.out.println(term with +$prec);
}
:
NUMBER rterm[$prec, 0]
|IDENTIFIER rterm[$prec, 0]
|'(' term[1200] ')' rterm[$prec, 0]
;
rterm[int pprec, int lprec]
@init{
System.out.println(rterm: pprec is +pprec+ lprec is +lprec);
}
:{(400 = $pprec) ($lprec 400)}?= ('+'^ term[400]
rterm[pprec,400]) { System.out.println(use + production);}
|{(300 = $pprec) ($lprec 300)}?= ('*'^ term[300]
rterm[pprec,300]) { System.out.println(use * production);}
|
;
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[il-antlr-interest: 31407] Re: [antlr-interest] Ident with ending In or Out word
Hi,
This is my sample grammar.. this did not work.. another thing is
that my variables and connectors both can have digits so I created Alpha
: LETTER (LETTER | DIGIT)*; for this but it also give an error.
primitiveType
: 'real'
| 'integer'
| 'char'
| 'boolean'
| 'void'
;
CONNECTOR : LETTER+ ('In' | 'Out');
ID: LETTER+ ;
fragment LETTER : ('a'..'z' | 'A'..'Z') ;
fragment DIGIT : '0'..'9';
INT : DIGIT+ ;
Regards
Roohul
S/W Engineer, LIU, Sweden
--- On Thu, 2/10/11, Bart Kiers bki...@gmail.com wrote:
From: Bart Kiers bki...@gmail.com
Subject: Re: [antlr-interest] Ident with ending In or Out word
To: Roohul roohu...@yahoo.com
Cc: ANTLR antlr-interest@antlr.org
Date: Thursday, February 10, 2011, 10:40 AM
On Thu, Feb 10, 2011 at 6:08 PM, Roohul roohu...@yahoo.com wrote:
Hi,
I am working on a grammar which have some variables ending with In or Out which
is treated as the connector between two components. I do not know how to handle
this.
For example:
real abcIn
real abcOut
these are treated as connectors. while abcI or abcOu will be treated as normal
variables.
You could handle this on a lexer level like this:
REAL : 'real'
;
CONNECTOR : Alpha+ ('In' | 'Out')
;
VARIABLE : Alpha+
;
fragmentAlpha : 'a'..'z' | 'A'..'Z' ;
(the order of the rules is important here!)
Regards,
Bart.
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[il-antlr-interest: 31408] Re: [antlr-interest] Ident with ending In or Out word
On Fri, Feb 11, 2011 at 2:27 PM, Roohul roohu...@yahoo.com wrote: Hi, This is my sample grammar.. this did not work.. another thing is that my variables and connectors both can have digits so I created Alpha : LETTER (LETTER | DIGIT)*; for this but it also give an error. The problem descriptions *did not work* and *also give an error* do not tell much. Care to elaborate? Bart. 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: 31410] Re: [antlr-interest] Ident with ending In or Out word
Sorry for that.. when i use only letters (a..z | A..Z) in the variables and connectors it give an error while creating an AST that no viable alternative at input 'real' and when creating variables with digits the grammar do not compile at all and give the following error. The following token definitions can never be matched because prior tokens match the same input: Alpha I hope that it is more elaboration.. Regards Roohul --- On Fri, 2/11/11, Bart Kiers bki...@gmail.com wrote: From: Bart Kiers bki...@gmail.com Subject: Re: [antlr-interest] Ident with ending In or Out word To: Roohul roohu...@yahoo.com Cc: ANTLR antlr-interest@antlr.org Date: Friday, February 11, 2011, 5:30 AM On Fri, Feb 11, 2011 at 2:27 PM, Roohul roohu...@yahoo.com wrote: Hi, This is my sample grammar.. this did not work.. another thing is that my variables and connectors both can have digits so I created Alpha : LETTER (LETTER | DIGIT)*; for this but it also give an error. The problem descriptions did not work and also give an error do not tell much. Care to elaborate? Bart. 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: 31412] Re: [antlr-interest] Ident with ending In or Out word
On Fri, Feb 11, 2011 at 9:17 AM, Roohul roohu...@yahoo.com wrote: Sorry for that.. when i use only letters (a..z | A..Z) in the variables and connectors it give an error while creating an AST that no viable alternative at input 'real' and when creating variables with digits the grammar do not compile at all and give the following error. The following token definitions can never be matched because prior tokens match the same input: Alpha I hope that it is more elaboration.. I would try moving some of that to real lexer items. You are using generated tokens, which depending on where they go, 'real', would be matched by the rule for ID, and there would be no way to generate that. I don't know where they end up, but I do remember it being recommended to avoid them until you have more experience. Given the error, I think that is what is happening here. Look at the sample grammars and how they handle keywords. My guess is that you are trying to do too much in the lexer, you can detect a lot of this at a much later state in the parser/analysis phase. But that is just parroting common advise on this list. Kirby Regards Roohul --- On Fri, 2/11/11, Bart Kiers bki...@gmail.com wrote: From: Bart Kiers bki...@gmail.com Subject: Re: [antlr-interest] Ident with ending In or Out word To: Roohul roohu...@yahoo.com Cc: ANTLR antlr-interest@antlr.org Date: Friday, February 11, 2011, 5:30 AM On Fri, Feb 11, 2011 at 2:27 PM, Roohul roohu...@yahoo.com wrote: Hi, This is my sample grammar.. this did not work.. another thing is that my variables and connectors both can have digits so I created Alpha : LETTER (LETTER | DIGIT)*; for this but it also give an error. The problem descriptions did not work and also give an error do not tell much. Care to elaborate? Bart. 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: 31413] [SPAM] [antlr-interest] [SPAM] Optional expression rule alternative
Is it possible to have a rule like this in ANTLR? rule[boolean z] : if (z) then rule1 else rule2 ; Thanks, -- O.L. 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: 31414] Re: [antlr-interest] [SPAM] [SPAM] Optional expression rule alternative
On 02/11/2011 12:34 PM, Olivier Lefevre wrote:
Is it possible to have a rule like this in ANTLR?
rule[boolean z] : if (z) then rule1 else rule2 ;
rule[boolean z]
: { z }? rule1
| rule2
;
Thanks,
-- O.L.
--
Kevin J. Cummings
kjch...@verizon.net
cummi...@kjchome.homeip.net
cummi...@kjc386.framingham.ma.us
Registered Linux User #1232 (http://counter.li.org)
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[il-antlr-interest: 31415] [SPAM] [antlr-interest] [SPAM] Re: [SPAM] [SPAM] Optional expression rule alternative
Great! Not to abuse but would you know in which section of The Definitive ANTLR Reference this mentioned? I couldn't find it. What is this syntax called? But in my real-world problem it was actually not a choice between rule1 and rule2 but a question of whether to allow an extra alternative in the z case without too much verbatim repetition, i.e. (again in pseudo-code): rule[boolean z] : rule1 | rule2 | ... | rule23 | (z ? rule24 : nothing) ; That is, allow rule24 if z otherwise stop at rule23. Thanks again, -- O.L. 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: 31416] Re: [antlr-interest] [SPAM] [SPAM] Re: [SPAM] [SPAM] Optional expression rule alternative
These are called Semantic Predicates. Section 12.1 in TDAR. Specifically, look at page 295 of the PDF. If the predicate evaluates to false, the alternative is effectively switched off. - Justin On 2/11/2011 1:04 PM, Olivier Lefevre wrote: Great! Not to abuse but would you know in which section of The Definitive ANTLR Reference this mentioned? I couldn't find it. What is this syntax called? But in my real-world problem it was actually not a choice between rule1 and rule2 but a question of whether to allow an extra alternative in the z case without too much verbatim repetition, i.e. (again in pseudo-code): rule[boolean z] : rule1 | rule2 | ... | rule23 | (z ? rule24 : nothing) ; That is, allow rule24 if z otherwise stop at rule23. Thanks again, -- O.L. 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: 31417] Re: [antlr-interest] [SPAM] [SPAM] Re: [SPAM] [SPAM] Optional expression rule alternative
On Fri, Feb 11, 2011 at 7:04 PM, Olivier Lefevre lefev...@yahoo.com wrote:
Great! Not to abuse but would you know in which section of
The Definitive ANTLR Reference this mentioned? I couldn't
find it. What is this syntax called?
It's called a validating semantic predicate which is explained in chapter
12 and 13.
But in my real-world problem it was actually not a choice
between rule1 and rule2 but a question of whether to allow
an extra alternative in the z case without too much
verbatim repetition, i.e. (again in pseudo-code):
rule[boolean z] :
rule1 | rule2 | ... | rule23 | (z ? rule24 : nothing) ;
That is, allow rule24 if z otherwise stop at rule23.
You can still do that:
rule [boolean z]
: {z}? (rule1 | rule2 | rule3 | ... | rule23 | rule24)
| (rule1 | rule2 | rule3 | ... | rule23)
;
Regards,
Bart.
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[il-antlr-interest: 31418] [SPAM] [antlr-interest] [SPAM] Re: Re: Optional expression rule alternative
On 2/11/2011 7:34 PM, Bart Kiers wrote:
You can still do that:
rule [boolean z]
: {z}? (rule1 | rule2 | rule3 | ... | rule23 | rule24)
| (rule1 | rule2 | rule3 | ... | rule23)
;
Yes but the rule1 | ... | rule23 train is huge: that is what
I meant by without too much verbatim repetition. So I'll
pack off the first 23 rules into yet another rule; not ideal
but that'll do.
I knew about predicates (although I haven't used them so far)
but they didn't occur to me in this context because they are
presented as a solution for grammar ambiguities, not as
switches driven from outside as here.
Thanks again,
-- O.L.
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[il-antlr-interest: 31419] [antlr-interest] beginner question - 'unexpected ast node' when generating from combined grammar
Hi,
I'm trying learn antlr by writing a parser for a simple HTML
templating language (in combination with reading the Definitive Antlr
Reference book - I'm only just past the calculator example so far
though.)
The parser should handle something like this:
{namespace My.Namespace}
{template MyTemplate}
hello
{if $name}
{print $name}
{else}
world
{/if}
br/
{/template}
My current attempt is to first build a simple version of the parser
without any actions, just to get it to parse valid input correctly:
grammar Test;
options { language = 'CSharp2'; }
doc: ns
WS*
(template)+
WS* ;
ns :'{namespace' WS+ DOTTED_IDENT WS* '}';
template:'{template' WS+ IDENT WS* '}' content '{/template}';
cmdSp :'{sp' WS* '/}';
cmdIf :'{if' WS* '}' content ('{elseif}' content)* ('{else}'
content)? WS* '{/if}' ;
anyCmd :cmdSp | cmdIf;
nonCmd :~(anyCmd); /* ~('{')*;*/
content :(anyCmd | nonCmd)*;
WS :' '|'\t'|'\r'|'\n';
IDENT :('a'..'z'|'A'..'Z'|'_') ('a'..'z'|'A'..'Z'|'_'|'0'..'9')*;
DOTTED_IDENT
:IDENT ((WS)* '.' (WS)* IDENT)*;
I was hoping to parse the first example minus the {$name} print
statement and the conditional in the {if} statement (i.e. the $name in
the {if}.)
When I try to generate the parser with the above definition, I get the
following warnings/errors:
Test.g:0:0: syntax error: buildnfa: AST:19:16: unexpected AST node: anyCmd
Test.g:19:14: set complement is empty
I'm guessing my use of ~(anyCmd) is incorrect, but I don't understand why?
If I try replacing that with ~('{')* as per the comment above, I get
these errors:
Test.g:19:18: Decision can match input such as '{else}' using
multiple alternatives: 1, 2
As a result, alternative(s) 2 were disabled for that input
... more errors like this ...
Test.g:19:18: The following alternatives can never be matched: 2
I thought this was specifying 'any character apart from {', so I don't
understand how '{else}' could be a match (or why there are multiple
alternatives - I thought I only specified one, unless * counts as
many?)
A brief explanation and/or a pointer to the section of the book I
should be reading would be most welcome.
Thanks,
Nick
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[il-antlr-interest: 31420] [SPAM] [antlr-interest] [SPAM] Chaining attributes
I wonder why it is not possible to chain attributes. E.g., $rule.start.type doesn't work. Since $rule.start.getType() does it's not a big deal but the former would be more elegant. -- O.L. 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.
