anchor.diff:      :   block
       ;
   
  -literal                                                
  +literal
       :   IntegerLiteral                                                # IntLit
       |   FloatingPointLiteral                                          # FloatLit
       |   CharacterLiteral                                              # CharLit
  
positive.code:     ;
  
  variableDefinition
      : mods='final'? type Identifier '=' 
                expression (',' Identifier '=' expression)*
      ;
  
  
negative.code:     |   expression op=('*'|'/'|'%') expression                           # Mul
      |   expression op=('+'|'-') expression                               # Add
      |   expression op=('<<' | '>>>' | '>>') expression                   # Shifts
      |   expression op=('<=' | '>=' | '>' | '<') expression               # Rel
      |   expression op=('==' | '!=') expression                           # Equ
      |   expression '&' expression                                        # BAnd
      |   expression '^' expression                                        # BXor
      |   expression '|' expression                                        # BOr
  