作为程序设计人员经常会遇到这样的情况，需要将某个指定的字符串表达式转换为算术表达式并计算其结果.使用Delphi的朋友可以在网上获取第三方控件来实现,而.Net框架类库并没有相关的处理类,正好在前不久的给一所大学开发的Web应用中也需要实现相关的处理.就抽空写了一个相关的处理类(实现了大部分的算术运算操作,需要其他运算可以在现有基础上扩展),现将部分代码贴出共大家参考,希望能够在交流中进步、互助中学习、探讨中深入:
//EnumExpress
using System;
namespace ExpressionTest{ /// <summary> /// EnumExpress 的摘要说明。 /// </summary> public enum EnumExpress { Add,//加号 Dec,//减号 Mul,//乘号 Div,//除号 Sin,//正玄 Cos,//余玄 Tan,//正切 ATan,//余切 Sqrt,//平方根 Pow,//求幂 None,//无 }}
//ExpressDeal
using System;
namespace ExpressionTest{ /// <summary> /// ExpressDeal 的摘要说明。 /// </summary> public class ExpressDeal { static ExpressDeal() { } private double CalculateExpress(string strExpression) { string strTemp=""; string strTempB=""; string strOne=""; string strTwo=""; double ReplaceValue=0; while (strExpression.IndexOf("+")!=-1 || strExpression.IndexOf("-")!=-1 || strExpression.IndexOf("*")!=-1 || strExpression.IndexOf("/")!=-1) { if (strExpression.IndexOf("*")!=-1) { strTemp=strExpression.Substring(strExpression.IndexOf("*")+1,strExpression.Length-strExpression.IndexOf("*")-1); strTempB=strExpression.Substring(0,strExpression.IndexOf("*"));
strOne=strTempB.Substring(GetPrivorPos(strTempB)+1,strTempB.Length-GetPrivorPos(strTempB)-1); strTwo=strTemp.Substring(0,GetNextPos(strTemp));
ReplaceValue=Convert.ToDouble(GetExpType(strOne))*Convert.ToDouble(GetExpType(strTwo));
strExpression=strExpression.Replace(strOne+"*"+strTwo,ReplaceValue.ToString()); } else if (strExpression.IndexOf("/")!=-1) { strTemp=strExpression.Substring(strExpression.IndexOf("/")+1,strExpression.Length-strExpression.IndexOf("/")-1); strTempB=strExpression.Substring(0,strExpression.IndexOf("/"));
strOne=strTempB.Substring(GetPrivorPos(strTempB)+1,strTempB.Length-GetPrivorPos(strTempB)-1); strTwo=strTemp.Substring(0,GetNextPos(strTemp));
ReplaceValue=Convert.ToDouble(GetExpType(strOne))/Convert.ToDouble(GetExpType(strTwo));
strExpression=strExpression.Replace(strOne+"/"+strTwo,ReplaceValue.ToString()); } else if (strExpression.IndexOf("+")!=-1) { strTemp=strExpression.Substring(strExpression.IndexOf("+")+1,strExpression.Length-strExpression.IndexOf("+")-1); strTempB=strExpression.Substring(0,strExpression.IndexOf("+"));
strOne=strTempB.Substring(GetPrivorPos(strTempB)+1,strTempB.Length-GetPrivorPos(strTempB)-1); strTwo=strTemp.Substring(0,GetNextPos(strTemp));
ReplaceValue=Convert.ToDouble(GetExpType(strOne))+Convert.ToDouble(GetExpType(strTwo));
strExpression=strExpression.Replace(strOne+"+"+strTwo,ReplaceValue.ToString()); } else if (strExpression.IndexOf("-")!=-1) { strTemp=strExpression.Substring(strExpression.IndexOf("-")+1,strExpression.Length-strExpression.IndexOf("-")-1); strTempB=strExpression.Substring(0,strExpression.IndexOf("-"));
strOne=strTempB.Substring(GetPrivorPos(strTempB)+1,strTempB.Length-GetPrivorPos(strTempB)-1); strTwo=strTemp.Substring(0,GetNextPos(strTemp));
ReplaceValue=Convert.ToDouble(GetExpType(strOne))-Convert.ToDouble(GetExpType(strTwo));
strExpression=strExpression.Replace(strOne+"-"+strTwo,ReplaceValue.ToString()); } } return Convert.ToDouble(strExpression); } private double CalculateExExpress(string strExpression,EnumExpress ExpressType) { double retValue=0; switch(ExpressType) { case EnumExpress.Sin: retValue=Math.Sin(Convert.ToDouble(strExpression)); break; case EnumExpress.Cos: retValue= Math.Cos(Convert.ToDouble(strExpression)); break; case EnumExpress.Tan: retValue= Math.Tan(Convert.ToDouble(strExpression)); break; case EnumExpress.ATan: retValue= Math.Atan(Convert.ToDouble(strExpression)); break; case EnumExpress.Sqrt: retValue= Math.Sqrt(Convert.ToDouble(strExpression)); break; case EnumExpress.Pow: retValue= Math.Pow(Convert.ToDouble(strExpression),2); break; } if (retValue==0) return Convert.ToDouble(strExpression); return retValue; } private int GetNextPos(string strExpression) { int[] ExpPos=new int[4]; ExpPos[0]=strExpression.IndexOf("+"); ExpPos[1]=strExpression.IndexOf("-"); ExpPos[2]=strExpression.IndexOf("*"); ExpPos[3]=strExpression.IndexOf("/"); int tmpMin=strExpression.Length; for (int count=1;count<=ExpPos.Length;count++) { if (tmpMin>ExpPos[count-1] && ExpPos[count-1]!=-1) { tmpMin=ExpPos[count-1]; } }
return tmpMin; } private int GetPrivorPos(string strExpression) { int[] ExpPos=new int[4]; ExpPos[0]=strExpression.LastIndexOf("+"); ExpPos[1]=strExpression.LastIndexOf("-"); ExpPos[2]=strExpression.LastIndexOf("*"); ExpPos[3]=strExpression.LastIndexOf("/"); int tmpMax=-1; for (int count=1;count<=ExpPos.Length;count++) { if (tmpMax<ExpPos[count-1] && ExpPos[count-1]!=-1) { tmpMax=ExpPos[count-1]; } }
return tmpMax; } public string SpiltExpression(string strExpression) { string strTemp=""; string strExp="";
while (strExpression.IndexOf("(")!=-1) { strTemp=strExpression.Substring(strExpression.LastIndexOf("(")+1,strExpression.Length-strExpression.LastIndexOf("(")-1); strExp=strTemp.Substring(0,strTemp.IndexOf(")")); strExpression=strExpression.Replace("("+strExp+")",CalculateExpress(strExp).ToString());
} if(strExpression.IndexOf("+")!=-1 || strExpression.IndexOf("-")!=-1 || strExpression.IndexOf("*")!=-1 || strExpression.IndexOf("/")!=-1) { strExpression=CalculateExpress(strExpression).ToString(); } return strExpression; } private string GetExpType(string strExpression) { strExpression=strExpression.ToUpper(); if (strExpression.IndexOf("SIN")!=-1) { return CalculateExExpress(strExpression.Substring(strExpression.IndexOf("N")+1,strExpression.Length-1-strExpression.IndexOf("N")),EnumExpress.Sin).ToString(); } if (strExpression.IndexOf("COS")!=-1) { return CalculateExExpress(strExpression.Substring(strExpression.IndexOf("S")+1,strExpression.Length-1-strExpression.IndexOf("S")),EnumExpress.Cos).ToString(); } if (strExpression.IndexOf("TAN")!=-1) { return CalculateExExpress(strExpression.Substring(strExpression.IndexOf("N")+1,strExpression.Length-1-strExpression.IndexOf("N")),EnumExpress.Tan).ToString(); } if (strExpression.IndexOf("ATAN")!=-1) { return CalculateExExpress(strExpression.Substring(strExpression.IndexOf("N")+1,strExpression.Length-1-strExpression.IndexOf("N")),EnumExpress.ATan).ToString(); } if (strExpression.IndexOf("SQRT")!=-1) { return CalculateExExpress(strExpression.Substring(strExpression.IndexOf("T")+1,strExpression.Length-1-strExpression.IndexOf("T")),EnumExpress.Sqrt).ToString(); } if (strExpression.IndexOf("POW")!=-1) { return CalculateExExpress(strExpression.Substring(strExpression.IndexOf("W")+1,strExpression.Length-1-strExpression.IndexOf("W")),EnumExpress.Pow).ToString(); } return strExpression; } }}
