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【CSharp】计算器类
作者:Dezai.CN / 发布于2012/5/10/ 605
<div>/******************************************************************
 * 创 建 人： SamWang
 * 创建时间： 2011-11-29
 * 描 述：
 * 计算器类：能直接对表达式进行计算，支持变量
 * 原 理： 将表达式按字符压入堆栈中，然后按照各操作符的级别进行处理
 * 版 本： V1.0 
 * 环 境： VS2005
******************************************************************/
using System;
using System.Collections.Generic;
using System.Text;
using System.Windows.Forms;
using System.Collections;

namespace LingDang.CRM.UI.Client
{
 public class Calculator
 {
 private string _expression;
 private Stack s;
 private string[] values;

 /// <summary>
 /// 构造函数
 /// </summary>
 /// <param name="expression">表达式</param>
 /// <param name="varValues">变量值数组</param>
 public Calculator(string expression, string[] varValues)
 {
 this._expression = expression.ToLower();
 s = new Stack();
 values = varValues;
 }

 /// <summary>
 /// 构造函数
 /// </summary>
 /// <param name="expression">表达式</param>
 public Calculator(string expression)
 {
 this._expression = expression;
 s = new Stack();
 }

 /// <summary>
 /// 总运行
 /// </summary>
 /// <returns></returns>
 public double Run()
 {
 string expression = PostFix();
 string[] aryString = expression.Split('|');

 foreach (string str in aryString)
 {
 if (IsNumber(str) || IsVarible(str[0]))
 {
 double d;
 if (IsVarible(str[0]))
 {
 d = Convert.ToDouble(GetValue(str[0]));
 }
 else
 {
 d = Convert.ToDouble(str.ToString());
 }
 AddOperands(d);
 }
 else
 {
 DoOperator(str);
 }

 }
 return (double)s.Pop();
 }


 private bool IsNumber(string str)
 {
 if (str.Length > 1)
 {
 return true;
 }
 else
 {
 return Char.IsDigit(str[0]);
 }
 }

 /// <summary>
 /// 判断是否为变量，变量范围为a-z
 /// </summary>
 /// <param name="c"></param>
 /// <returns></returns>
 private bool IsVarible(char c)
 {
 if (c >= 'a' && c <= 'z')
 {
 return true;
 }
 else
 {
 return false;
 }
 }


 private void AddOperands(double val)
 {
 s.Push(val);
 }

 /// <summary>
 /// 得到公式左右运算数
 /// </summary>
 /// <param name="left"></param>
 /// <param name="right"></param>
 /// <returns></returns>
 private bool GetTwoOperands(out double left, out double right)
 {
 try
 {
 right = (double)s.Pop();
 left = (double)s.Pop();
 }
 catch (InvalidOperationException)
 {
 right = 0;
 left = 0;
 return false;
 }
 return true;
 }

 /// <summary>
 /// 计算操作
 /// </summary>
 /// <param name="op">运算符</param>
 private void DoOperator(string op)
 {
 double left, right;
 bool result = GetTwoOperands(out left, out right);
 if (result)
 {
 switch (op)
 {
 case "+": s.Push(left + right); break;
 case "-": s.Push(left - right); break;
 case "*": s.Push(left * right); break;
 case "/":
 if (right == 0.0)
 {
 s.Clear();
 //Divide by 0!
 throw new Exception("除数不能为零");
 }
 else
 s.Push(left / right);
 break;
 case "^":
 s.Push(Math.Pow(left, right));
 break;
 }
 }
 else
 {
 s.Clear();
 }
 }

 /// <summary>
 /// 解析为后缀表达式
 /// </summary>
 /// <returns></returns>
 public string PostFix()
 {
 string str = this._expression + "#";
 char tempc;
 char[] chars = str.ToCharArray();
 Stack ts = new Stack();
 ts.Push('#');
 string str1 = "";
 string tmpStr = "";
 bool isNum = false;
 foreach (char c in chars)
 {
 if (Char.IsDigit(c) || IsVarible(c) || c == '.')
 {
 tmpStr += c.ToString();
 isNum = true;
 }
 else
 {
 if (isNum)
 {
 str1 += tmpStr + "|";
 tmpStr = "";
 }
 isNum = false;
 if (c == ')')
 {
 for (tempc = Convert.ToChar(ts.Pop()); tempc != '('; tempc = Convert.ToChar(ts.Pop()))
 str1 += tempc.ToString() + "|";
 }
 else
 {
 for (tempc = Convert.ToChar(ts.Pop()); Isp(tempc) > Icp(c); tempc = Convert.ToChar(ts.Pop()))
 str1 += tempc.ToString() + "|";
 ts.Push(tempc);
 ts.Push(c);
 }
 }
 }
 return str1.Substring(0, str1.Length - 1);
 }

 /// <summary>
 /// 根据变量名得到对应的值
 /// </summary>
 /// <param name="c">变量名：A-Z</param>
 /// <returns></returns>
 private string GetValue(char c)
 {
 string result = "0";
 //变量对应的数组位置
 int index = Convert.ToInt32(c) - Convert.ToInt32('a');
 if (index < values.Length)
 {
 result = values[index].ToString();
 }
 return result;
 }

 private int Isp(char c)
 {
 int k;
 switch (c)
 {
 case '#': k = 0; break;
 case '(': k = 1; break;
 case '^': k = 7; break;
 case '*':
 case '/':
 case '%': k = 5; break;
 case '+':
 case '-': k = 3; break;
 case ')': k = 8; break;
 default:
 //Unknown operator!
 throw new Exception("无效操作符："+c.ToString());
 }
 return k;
 }

 private int Icp(char c)
 {
 int k;
 switch (c)
 {
 case '#': k = 0; break;
 case '(': k = 8; break;
 case '^': k = 6; break;
 case '*':
 case '/':
 case '%': k = 4; break;
 case '+':
 case '-': k = 2; break;
 case ')': k = 1; break;
 default:
 //Unknown operator!
 throw new Exception("无效操作符：" + c.ToString());
 }
 return k;
 }
 }
}
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