控制台下的一个表达式计算器，支持带符号小数+-*/以及指数运算，可以输入（）来调整运算优先级，比如：输入1-2*(3+4^(1/2))=-9-Console expression under a calculator, a small number of support signed+-*/And index calculation, can enter () to adjust the priority operations, such as: Enter the 1-2* (3+ 4 ^ (