anchor.diff:  //变量
   VAR : [A-Z][a-zA-Z0-9_]*;
   
  +//指数运算
  +EXPONENITIATION : '**';
  +//位运算
  +BITWISE_AND : '&';
  +BITWISE_OR : '?';
  +BITWISE_EXCLUSIVE_OR : '^';
  +BITWISE_COMPLEMENT : '~';
   //加号
   PLUS : '+';
   //减号、经典否定关键字
  
positive.code: simple_arithmetic_expr :
      integer |
      (MINUS)? VAR |
      (integer | (MINUS)? VAR) (arithmetic_op (natural_number | VAR))* ;
  
  //四则运算算术表达式，加括号
  simple_arithmetic_expr2 :
  
negative.code: natural_number : POSITIVE_INT | ZERO;
  //四则运算符
  arithmetic_op : PLUS | MINUS | STAR | SLASH;
  //二元位运算
  bitwise_op : BITWISE_AND | BITWISE_OR | BITWISE_EXCLUSIVE_OR;
  //二元运算符
  binary_op : arithmetic_op | bitwise_op | EXPONENITIATION;
  //一元运算符
  unary_op : BITWISE_COMPLEMENT;
  //数字
  bit_number : unary_op? natural_number;
  //关系运算符(comparison predicates)
  relation_op : LESS_THAN | LEQ | GREATER_THAN | GEQ | EQUAL | DOUBLE_EQUAL | NEQ;
  
  