On 31 Mar, 16:32, pk  wrote:   
   > I'm trying to write a recursive descent parser for this grammar   
      
   I use the following grammar for lexertl (http://www.benhanson.net/   
   lexertl.html):   
      
    ->    
    ->  | '|'   
    ->    
    ->  |    
    ->    
    -> charset | macro | '('')' |    
    -> '?' | '*' | '+' | '{n[,[m]]}'   
      
   The rules  and  were only introduced to simplify the   
   processing, as I use a bottom up parser.   
      
   I hope that helps.   
      
   Regards,   
      
   Ben   
      
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