说明：  功能：给出一个字符串表达式(可以是任意复杂的字符串表达式)，计算字符串表达式的值. <br> 特性： <br> 1：用户可以添加其它运算符号 ，也就是说用户可以制定新的运算符，引擎中不存在的运算符号，当然具体的运算类还是得用户提供. <br> 2: 可以修改运算符的性质，你可以使得3*3=6，只要将*的运算类指向expression.DAdd就可以了,具体如何操作，ReadMe中有说明.<br> 3:可以使操作符运算具有多种形态。您即可以用“+”表示加法运算，也可以用" 加法" 表示加法运算.<br> 强调一下：,本引擎的最大特点就是： 用户可以添加自己的运算符号，而无需修改计算引擎本身.<br>
(function : given a string expression (which may be arbitrary complex string expression), and calculating the value of the string expression. Lt; Brgt; Characteristics : lt; Brgt; A : Users can add other computing symbols This means users can develop new Operators the engine does not exist arithmetic symbols, of course, the specific type of operation must also be available. lt; brgt; 2 : Operators can modify the nature, you can make 3* 3 = 6, as long as the computing category* expression.DAdd can point to a specific example Dr operation, ReadMe is described. lt; brgt; 3 : It will make operation Operator with a variety of patterns. That is, you can use "," said Ghaffar Operators can also use quot quot said Ghaffar addition operations. Lt; Brgt; Stress : The engine is the biggest )