此源码是用C写的，用于一般表达式的求值。由于是用C写的，可以跨平台使用。你也可以取其中的功能函数嵌入到其他项目中作为一个功能组件。-This source code is written in C, for the general expression to be evaluated. Because it is written in C, can be cross-platform use. You can also take one of the feature functions embe