anchor.diff:  
   external_declaration:
   COMMENT | LINE_COMMENT | preprocessor_declaration
  -|function_definition
  +| function_definition
   | declaration 
   | class_interface
   | class_implementation
  
positive.code:   '=' | '*=' | '/=' | '%=' | '+=' | '-=' | '<<=' | '>>=' | '&=' | '^=' | '|=';
  
  conditional_expression : logical_or_expression 
    ('?' logical_or_expression ':' logical_or_expression)? ;
  
  constant_expression : conditional_expression ;
  
  
negative.code: iteration_statement
    : 'while' '(' expression ')' statement
    | 'do' statement 'while' '(' expression ')' ';'
    | 'for' '(' ((declaration_specifiers init_declarator_list) | expression)? ';' expression? ';' expression? ')' statement
    | 'for' '(' type_variable_declarator 'in' expression? ')' statement ;
  
  jump_statement
    : 'goto' identifier ';'
  