anchor.diff:      :   block
       ;
   
  -literal                                                
  +literal
       :   IntegerLiteral                                                # IntLit
       |   FloatingPointLiteral                                          # FloatLit
       |   CharacterLiteral                                              # CharLit
  
positive.code:     ;
  
  formalParameterList
      :   formalParameter (',' formalParameter)* 
      ;
  
  formalParameter
  
negative.code:     ;
  
  variableDefinition
      : mods='final'? type Identifier '='
                expression (',' Identifier '=' expression)*
      ;
  
  