表达式求值计算器,例如输入-(-1-(-1*2+3)/4-5+6/7*8-9)输出7.6428571428571432，还有些bug待修正,例如最多只能表示32位精度等。(欢迎广大高手拍砖)-Expression evaluation calculator, such as input- (-1- (-1* 2+3)/4-5+6/7* 8-9) output 7.6428571428571432, and some bug to be modified, for example, that a