该类有以下特点： 1.支持字符串中含有各种常用函数，如"7.5+sin(6*ln(8))/exp(5)" 2.具有很好的纠错能力，能检查出表达式中括号是否配对、库函数是否正确 3.运算过程中能检查并判断出各种异常，如除数为0、开方函数sqrt(x)中x<0，反余弦函数acos(x)中的x<-1或x>1等 4.支持积分、求方程，算术表达式中可含有x，计算时将用类中的成员变量xx代替-Such has the following characteristics: 1. To support the string contains a variety of commonly used functions, such as　7.5+ Sin (6* ln (8))/exp (5)　2. Have good error-correcting capabilities, to check brackets if the expression matching library function is correct 3. computing process to examine and determine the various anomalies, such as the divisor is 0, prescribing function sqrt (x) in x <0, anti-cosine acos (x) The x <-1 or x> 1 4. support the points, and equations, arithmetic expressions may contain x, the calculation will be used to class members in lieu of variable xx