parser including LL(1), SLR, Operator-Precedence Parser with LL(1), SLR, Operator-Precedence Rule 符号说明: ~ : 空/ε # : 终结符 样例说明: example.in 是未消除左递归的算术表达式文法 example2.in 是消除左递归的算术表达式文法