[antlr-interest] Error in HTML lexer for Comments

[Matthew Ford]

Hi all,
I think there is an error in the Comment rule in the html.g example

 was {LA(2)!='-' && LA(3)!='>'}? '-' // allow '-' if not "-->"
   actually     and if not "-?>" and if not "--?"  these cases cause early
termination of the comment rule befor end of comment reached.

 should be  {(LA(2)!='-')  || (LA(2)=='-' && LA(3)!='>') }? '-' // allow '-'
and "--?" and "-?>" but not "-->"

replacement rule follows below.

You may need to check any other rules you have coded based on this template
of testing for a termination string.  I found this problem while  trying to
get another rule to work that was based on this template.

matthew


// multiple-line comments
protected
COMMENT_DATA
 : ( /* '\r' '\n' can be matched in one alternative or by matching
    '\r' in one iteration and '\n' in another.  I am trying to
    handle any flavor of newline that comes in, but the language
    that allows both "\r\n" and "\r" and "\n" to all be valid
    newline is ambiguous.  Consequently, the resulting grammar
    must be ambiguous.  I'm shutting this warning off.
    */
   options {
    generateAmbigWarnings=false;
   }
  :
   {(LA(2)!='-')  || (LA(2)=='-' && LA(3)!='>') }? '-' // allow '-' and
"-?>" and "--?" but not "-->"
                   //  was {LA(2)!='-' && LA(3)!='>'}? '-' // allow '-' if
not "-->" and if not "-?>" and if not "--?"
  | '\r' '\n'  {newline();}
  | '\r'   {newline();}
  | '\n'   {newline();}
  | ~('-'|'\n'|'\r')
  )*
 ;


----------------------------------------------------
Dr. Matthew.Ford
Forward Computing & Control Pty. Ltd.
www.forward.com.au


 

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