anchor.diff:      ;
       
   version
  -    : varName                                               #VersionVariableName
  -    | namedConstant Colon expression                        #VersionedNamedAbbreviation
  -    | LeftBracket updateList RightBracket ATR version       #UpdationList
  -    | LeftBracket RightBracket ATR version                  #NoUpdateList
  +    : varName ( Colon expression )?                         #VersionVariableName
  +    | LeftBracket (updateList)? RightBracket ATR version    #UpdationList
       ;
       
   notExpr
  
positive.code: arrName : Identifier ;
  
  numberList
      : number
      | number numberList
      ;
  
  number 
  
negative.code:     ;
      
  INT : 'i';
  FP : 'fp';
  
  Whitespace
      :   [ \t]+ -> skip
  