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