anchor.diff:      :  '"' ( ESC_SEQ | ~('\\'|'"') )* '"'
       ;
   
  -PV
  +PCHANNEL
       :  '\'' ( ESC_SEQ | ~('\\'|'\'') )* '\''
       ;
   
  
positive.code: }
  }
  
  singlePv returns [FormulaAst result]
      :   channel EOF {result = $channel.result;}
      ;
  
  
negative.code:     ;
  
  channel returns [FormulaAst result]
      :   PCHANNEL {result = channelFromToken($PCHANNEL.text);}
      ;
  
  numericLiteral returns [FormulaAst result]
  