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

[Mark Buckle]

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 yci.com [mailto:mzukowski at yci.com] 
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 wanadoo.fr] 
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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