C#计算器(递归，WebService) 支持加减乘除括号等 (一)

public class Calculator : System.Web.Services.WebService
{
/// <summary>
/// 实现混合运算
/// </summary>
/// <param name="content">表达式</param>
/// <returns></returns>
[WebMethod]
public double parse(String content)
{
//标识括号
int startIndex = content.LastIndexOf("(");
if (startIndex != -1)
{
int endIndex = content.IndexOf(")", startIndex);
int len = endIndex - startIndex - 1;
double d = parse(content.Substring(startIndex + 1, len));
return parse(content.Substring(0, startIndex) + d + content.Substring(endIndex + 1));
}

//标识运算符
int index = content.IndexOf("+");
if (index != -1)
{
return parse(content.Substring(0, index)) + parse(content.Substring(index + 1));
}
index = content.LastIndexOf("-");
if (index != -1)
{
return parse(content.Substring(0, index)) - parse(content.Substring(index + 1));
}
index = content.IndexOf("*");
if (index != -1)
{
return parse(content.Substring(0, index)) * parse(content.Substring(index + 1));
}
index = content.LastIndexOf("/");
if (index != -1)
{
return parse(content.Substring(0, index)) / parse(content.Substring(index + 1));
}
return Double.Parse(content);

}
}