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

[Mark Buckle]

Ugh, groan.
Well if that's how it is, that's how it is.  
BTW what is sematic predicate hoisting ?

-----Original Message-----
From: lgcraymer [mailto:lgc at mail1.jpl.nasa.gov] 
Sent: 08 March 2004 21:33
To: antlr-interest at yahoogroups.com
Subject: [antlr-interest] Re: expecting IDENT, found 'x'


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' ;
> 
> 
> 
> 
> 
> 
> 
>  
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> 
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