anchor.diff:  
   options {  
     output=AST; 
  -}  
  +  ASTLabelType=CommonTree;
  +}
   
   tokens {
   	STATEMENTS;
  
positive.code: 	DEFINITION;
  	TEST;
  	FUNCTION;
  }
  
  /*
  
negative.code: 
  arithm_variable
  	:	arithm_constant
  	|	(NEGATIVE)? BRACKET_OPEN arithm_constant BRACKET_CLOSE -> ^(NEGATIVE arithm_constant)
  	;
  
  expr	:	addition;
  