普通一重定积分的表达式计算
吴总在数值计算支持库写的算式解析，貌似有bug？还是我不会用，重新写了下
支持的常量：
e 2.7182818284590452353602874713527L
pi 3.1415926535897932384626433832795L
c 2.99792458e8L //光速
G 6.67310e-11L //重力常数
h 6.6260687652e-34L //普朗克常数
支持的运算符：
'+','-','*','/','^','%'
支持的函数名
{ "ln","lg","sin","cos","tan","exp","sinh","cosh","tanh","asin","acos","atan",
"sqrt","abs","ceil","floor","fabs","cbrt","log2", "round" }
