[antlr-interest] Re: expecting IDENT, found 'x'

[lgcraymer]

It's either/or.  You can identify them, but not as literals if you are might use them as identifiers elsewhere--use semantic predicates to 
match text.  Or, if you do use them as literals, then you need a parser rule that spells out these items as alternatives:
id :  ID | "begin" | "end" ;

and use id everywhere you might have otherwise used ID.  This is much cleaner with semantic predicate hoisting--you can have 
keyword rules..

--Loring


--- In antlr-interest at yahoogroups.com, Mark Buckle <mark.buckle at i...> wrote:
> 
> Hi All,
> 
> I've read the docs, experimented with the tokens{} section in the lexer and
> "literals" in the parser, and still
> not quite got to grips with what is going on with tokens and identifers in
> ANTLR.
> 
> What I'd like to be able to do with my parser is to treat keywords in the
> language only as keywords in the places specified.
> 
> Eg 
> Statement_block
> 	:			"begin"
> 				( statement SEMI ) +
> 				"end"
> 	;
> 
> and have BEGIN and END only treated as distinguished keywords when defining
> a block like this, and have them treated as identifiers elsewhere.
> From what I've read, it seems to be suggested that ANTLR can do this, but
> I've not been able to get it to work.  Have I misunderstood things ?
> I'm trying to write a parser for a language which has a lot of keywords
> which aren't reserved words.  I've gone through the tedium of
> doing this in the past in lex/yacc for another language, and had to add the
> ambiguous keywords to a list of identifiers, which wasn't always possible
> without triggering a lot of reduce/reduce conflicts.  I was hoping that
> ANTLR, being ll(k) would be able to use its current context to inform the
> lexer
> whether something would be an identifier or keyword from the current rule
> being tried.
> 
> Cheers Mark.
> 
> 
> 
> 
> -----Original Message-----
> From: mzukowski at y... [mailto:mzukowski at y...] 
> Sent: 08 March 2004 17:12
> To: antlr-interest at yahoogroups.com
> Subject: RE: [antlr-interest] expecting IDENT, found 'x'
> 
> 
> You are using ":" (in the parser) as a literal which it really shouldn't be,
> unless it can be part of an identifier.  
> 
> Instead you should have this in your lexer:
> COLON        :     ':'   ;     
> 
> And in the parser you should use COLON, not ":".
> 
> Read the docs on literals to get an idea of what was happening and when to
> use "something" in the parser.
> 
> Monty
> 
> -----Original Message-----
> From: jc_lelann [mailto:jc.lelann at w...] 
> Sent: Saturday, March 06, 2004 6:58 AM
> To: antlr-interest at yahoogroups.com
> Subject: [antlr-interest] expecting IDENT, found 'x'
> 
> Hi !
> 
> Could someone explain me why my parser returns the following message ?
> 
> java Test < test.txt
> line 1:10: expecting IDENT, found 'x'
> exception: line 1:12: unexpected char: ':'
> 
> I am new to antlr.
> Thanks
> 
> JC
> 
> 
> 
> My grammar :
> 
> // content of my test file :
> 
> // constant x : integer := 4;
> // constant x,y,z : integer := 5;
> // constant x,y,z : integer := 5+5*2;
> 
> 
> class TestParser extends Parser;
> options {
>     buildAST = true;
>     defaultErrorHandler = true;     // Generate parser error handlers
> }
> 
> mytext : 
>         (constant_declaration)* EOF! ;
> 
> constant_declaration : 
>         CONSTANT! identifier_list ":"! subtype_indication ":="! expression
> ";"! ; identifier_list : 
>         identifier (","! identifier)*
> ;
> identifier : 
>         IDENT
> ;
> subtype_indication : 
>         IDENT
> ;
> expression:     
>         additiveExpression
> ;
> // addition/subtraction
> additiveExpression:     
>         multiplicativeExpression((PLUS^ | MINUS^)
> multiplicativeExpression)*
> ;
> // multiplication/division   
> multiplicativeExpression:     
>         powerExpression ( (STAR^ | DIV^ ) powerExpression )*
> ;
> powerExpression: 
>         unaryExpression ( POWER^ unaryExpression)*
> ;
> unaryExpression:
>         MINUS^ unaryExpression
>       |     primaryExpression
> ;
> primaryExpression:
>         NUMBER
>       |     LPAREN! additiveExpression RPAREN!
>       ;
> 
> class TestLexer extends Lexer;
> options {
> 	exportVocab=Test;      // call the vocabulary "Java"
> }
> 
> tokens {
>     CONSTANT ="constant";
> }
> 
> WS    :(    ' ' | '\t' | '\n' | '\r' )
>         { _ttype = Token.SKIP; }
> ;
> //-------------
> // OPERATORS
> //-------------
> LPAREN      :     '('   ;     
> RPAREN      :     ')'   ;
> SEMI        :     ';'   ;     
> DOT         :     '.'   ;
> DIV         :     '/'   ;     
> PLUS        :     '+'   ;
> MINUS       :     '-'   ;     
> STAR        :     '*'   ;
> POWER       :     '^'   ;    
> 
> // Rule for IDENTIFIER: testLiterals is set to true.
> IDENT
> 	options {testLiterals=true;}
>             : ( 'a'..'z' )+
> 	;
> 
> //for both integer and real number
> 
> NUMBER : (DIGIT)+ ( '.' (DIGIT)+ )? ;
> 
> //for numbers
> protected
> DIGIT :     '0'..'9' ;
> 
> 
> 
> 
> 
> 
> 
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
> 
> This e-mail may contain information that is privileged, confidential or
> otherwise protected from disclosure. It must not be used by, or its 
> contents copied or disclosed to, persons other than the intended 
> recipient. However, the contents of this e-mail may be intercepted, 
> monitored or recorded by Insurance Technology Solutions Limited for 
> the purposes of ensuring compliance with its policies and procedures. 
> Any liability (in negligence or otherwise) arising from any third party
> acting, or refraining from acting, on any information contained in this
> e-mail is excluded.
> 
> Any views expressed in this message are those of the individual
> sender and do not necessarily represent the views of
> Insurance Technology Solutions Limited.
> 
> If you have received this e-mail in error please notify the
> originator of the message.
> 
> Scanning of this message and addition of this footer is performed
> by SurfControl E-mail Filter software in conjunction with 
> virus detection software.



 
Yahoo! Groups Links

<*> To visit your group on the web, go to:
     http://groups.yahoo.com/group/antlr-interest/

<*> To unsubscribe from this group, send an email to:
     antlr-interest-unsubscribe at yahoogroups.com

<*> Your use of Yahoo! Groups is subject to:
     http://docs.yahoo.com/info/terms/