anchor.diff:  
   stringLiteral
       :   StringLiteral
  +    ;
  +
  +variable
  +    :   Variable
  +    ;
  +
  +Variable
  +    :   ('a'..'z')('a'..'z'|'A'..'Z'|'_'|'0'..'9')*
       ;
   
   NumberLiteral
  
positive.code: statement
      :   print
      |   end
      ;
  
  print
  
negative.code:     ;
  
  expression
      :   numberLiteral | stringLiteral | booleanLiteral | variable
      |   expression '=' expression
      |   expression 'AND' expression
      |   twoaryfunction '(' expression ',' expression ')'
      ;
  
  twoaryfunction
      :   'mod'
      ;
  
  booleanLiteral
      :   'TRUE' | 'FALSE'
      ;
  
  numberLiteral
  