[antlr-interest] RE : Re: How can I ignore reserved words in certain cases ?

JeanChristophe Gautier jchgautier at yahoo.fr
Thu Nov 30 04:59:08 PST 2006


Hi,
 
 Thanks for your help but that doesn't solve my problem. We have a hundred or so key words (such as print) declared in the lexer, all of which should be accepted as a STRING. We could always do as you suggested but we would have a parser rule several lines long and we would need to modify it whenever we added a new key word. Is there no way to simply ignore the key word tokens for certain rules?
 
 Many thanks,
 JC
 

Micheal J <open.zone at virgin.net> a écrit :   Message    
Hi,

I am writing a command line editor that has reserved words, such as
"print", that should accept, at times, any string value. For example the
following should be allowed:

print hello
print print

The grammar is defined as follows:



class ExprParser extends Parser;

options {
        k = 2;
    buildAST=true;
}

expr: expr1;

expr1: PRINT STRING; 

==> expr: PRINT ( STRING | PRINT ) ;

 



class ExprLexer extends Lexer;

options {
    k=2;
    charVocabulary='\u0000'..'\u007F';
    testLiterals = false;
}

tokens {
        PRINT = "print";
}

STRING options { testLiterals = true; } : ('a'..'z')+;

WS    : ( ' '
        | '\r' '\n'
        | '\n'
        | '\t'
        )
        {$setType(Token.SKIP);}
      ;


Obviously the second example ("print print") does not work
 because the
token PRINT takes priority since we have testLiterals = true (note
    that
this example is taken from a more complex grammar).

The    question is: how do I, under certain circumstances, ignore reserved
word    tokens?

Bythe way, I am currently using antlr 2.7. 
    
   ==> ANTLR2's latest version is 2.7.7 

Many    thanks,
JC



      

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