如何把字符串 "100*23/(23+78)" 计算他的值?

Question

如何把字符串 "100*23/(23+78)"  计算他的值? 编成语言: c# .业务背景：用户定义的公式为 a*b/(c+d) . 系统把里面的参数替换后为 "100*23/(23+78)"
问题是如何计算它的值。

Answer 1

或许用正则表达式可以把各个部分提取出来就可以了.
甚至可以用string类的split()也可以.

Answer 2

可以用jscript命名空间里的函数

Answer 3

using System;
using System.Text;
using System.CodeDom.Compiler;
using Microsoft.VisualBasic;
using System.Reflection;class Evaluator
    {
        //private static CodeDomProvider comp = new CSharpCodeProvider();
        private static CodeDomProvider comp = new VBCodeProvider();
        private static CompilerParameters cp = new CompilerParameters();
        private static MethodInfo mi;        public static object Eval(string expression)
        {
            StringBuilder codeBuilder = new StringBuilder();            codeBuilder.AppendLine("Imports System");
            codeBuilder.AppendLine("Imports System.Math");
            codeBuilder.AppendLine("Imports Microsoft.VisualBasic");
            codeBuilder.AppendLine();
            codeBuilder.AppendLine("Public Module Mode");
            codeBuilder.AppendLine("   Public Function Func() As Object");
            codeBuilder.AppendLine("        Return " + expression);
            codeBuilder.AppendLine("   End Function");
            codeBuilder.AppendLine("End Module");            cp.ReferencedAssemblies.Add("System.dll");
            cp.ReferencedAssemblies.Add("Microsoft.VisualBasic.dll");
            cp.GenerateExecutable = false;
            cp.GenerateInMemory = true;            string code = codeBuilder.ToString();
            CompilerResults cr = comp.CompileAssemblyFromSource(cp, code);            if (cr.Errors.HasErrors)
            {
                return null;
            }
            else
            {
                Assembly a = cr.CompiledAssembly;
                Type t = a.GetType("Mode");
                //object mode = a.CreateInstance("Mode");
                mi = t.GetMethod("Func", BindingFlags.Static | BindingFlags.Public);
                return mi.Invoke(null, new object[0]);
            }
        }
    }//........
public static void Main()
{
    Console.WriteLine(Evaluator.Eval("100*23/(23+78)").ToString());
    Console.ReadKey();
}

Answer 4

crossbowvic(漫步的兔子),你太强了!

Answer 5

不知道这个是不是你想要的.
VB的代码.你可以仔细看看,应该可以看明白.
Module modCalculate    Const pi As Double = 3.1415926535    Public Function CalculateString(ByVal Exppression As String, ByRef Good As Boolean, ByVal xxx As Double) As Double        Dim isg As Boolean
        Dim ExppressionLength As Integer
        Dim pp As Integer
        pp = 1
        ExppressionLength = Len(Exppression)
        CalculateString = E(UCase(Exppression), isg, pp, xxx)
        Good = isg
        If pp <= ExppressionLength Then Good = False
    End Function
    Private Function E(ByVal Exppression As String, ByRef Good As Boolean, ByRef Position As Integer, ByVal xxx As Double) As Double
        Dim tmp1 As Double
        Dim tmp2 As Double
        Dim isg As Boolean
        On Error GoTo Eerr        tmp1 = T(Exppression, isg, Position, xxx)
        If Match(Exppression, "+", Position) Then
            Position = Position + 1
            tmp2 = E2(Exppression, isg, Position, xxx)
            If Not (isg) Then
                Good = False
                Exit Function
            End If
            E = tmp1 + tmp2
        Else
            If Match(Exppression, "-", Position) Then
                Position = Position + 1
                tmp2 = E2(Exppression, isg, Position, xxx)
                If Not (isg) Then
                    Good = False
                    Exit Function
                End If
                E = tmp1 - tmp2
            Else                E = tmp1
            End If
        End If
        Good = isg
        Exit Function
Eerr:
        Good = False
    End Function
    Private Function E2(ByVal Exppression As String, ByRef Good As Boolean, ByRef Position As Integer, ByVal xxx As Double) As Double
        Dim tmp1 As Double
        Dim tmp2 As Double
        Dim isg As Boolean
        tmp1 = T2(Exppression, isg, Position, xxx)
        If Match(Exppression, "+", Position) Then
            Position = Position + 1
            tmp2 = E2(Exppression, isg, Position, xxx)
            If Not (isg) Then
                Good = False
                Exit Function
            End If            E2 = tmp1 + tmp2
        Else
            If Match(Exppression, "-", Position) Then
                Position = Position + 1
                tmp2 = E2(Exppression, isg, Position, xxx)
                If Not (isg) Then
                    Good = False
                    Exit Function
                End If                E2 = tmp1 - tmp2
            Else                E2 = tmp1
            End If
            Good = isg
        End If
    End Function
    Private Function T(ByVal Exppression As String, ByRef Good As Boolean, ByRef Position As Integer, ByVal xxx As Double) As Double
        Dim tmp1 As Double
        Dim tmp2 As Double
        Dim isg As Boolean        tmp1 = F(Exppression, isg, Position, xxx)
        If isg Then
            If Match(Exppression, "\", Position) Then
                Position = Position + 1
                tmp2 = T2(Exppression, isg, Position, xxx)
                If Not (isg) Then
                    Good = False
                    Exit Function
                End If                T = CInt(tmp1) \ CInt(tmp2)
            Else
                If Match(Exppression, "^", Position) Then
                    Position = Position + 1
                    tmp2 = T2(Exppression, isg, Position, xxx)
                    If Not (isg) Then
                        Good = False
                        Exit Function
                    End If                    T = tmp1 ^ tmp2
                Else
                    If Match(Exppression, "*", Position) Then
                        Position = Position + 1
                        tmp2 = T2(Exppression, isg, Position, xxx)
                        If Not (isg) Then
                            Good = False
                            Exit Function
                        End If                        T = tmp1 * tmp2                    Else
                        If Match(Exppression, "/", Position) Then
                            Position = Position + 1
                            tmp2 = T2(Exppression, isg, Position, xxx)
                            If Not (isg) Then
                                Good = False
                                Exit Function
                            End If                            T = tmp1 / tmp2
                        Else                            T = tmp1
                        End If
                    End If
                End If
            End If
        End If
        Good = isg
    End Function
    Private Function T2(ByVal Exppression As String, ByRef Good As Boolean, ByRef Position As Integer, ByVal xxx As Double) As Double
        Dim tmp1 As Double
        Dim tmp2 As Double
        Dim isg As Boolean
        tmp1 = F2(Exppression, isg, Position, xxx)
        If isg Then
            If Match(Exppression, "\", Position) Then
                Position = Position + 1
                tmp2 = T2(Exppression, isg, Position, xxx)
                If Not (isg) Then
                    Good = isg
                    Exit Function
                End If
                T2 = CInt(tmp1) \ CInt(tmp2)
            Else
                If Match(Exppression, "^", Position) Then
                    Position = Position + 1
                    tmp2 = T2(Exppression, isg, Position, xxx)
                    If Not (isg) Then
                        Good = isg
                        Exit Function
                    End If
                    T2 = tmp1 ^ tmp2
                Else
                    If Match(Exppression, "*", Position) Then
                        Position = Position + 1
                        tmp2 = T2(Exppression, isg, Position, xxx)
                        If Not (isg) Then
                            Good = isg
                            Exit Function
                        End If
                        T2 = tmp1 * tmp2
                    Else
                        If Match(Exppression, "/", Position) Then
                            Position = Position + 1
                            tmp2 = T2(Exppression, isg, Position, xxx)
                            If Not (isg) Then
                                Good = isg
                                Exit Function
                            End If
                            T2 = tmp1 / tmp2
                        Else
                            T2 = tmp1
                        End If '/
                    End If '*                End If '^
            End If '\
        End If
        Good = isg
    End Function
    Private Function F(ByVal Exppression As String, ByRef Good As Boolean, ByRef Position As Integer, ByVal xxx As Double) As Double
        Dim Tmp As Double
        Dim isg As Boolean
        Tmp = OpDigital(Exppression, isg, Position, xxx)
        If Not (isg) Then Tmp = g(Exppression, isg, Position, xxx)
        F = Tmp
        Good = isg
    End Function
    Private Function F2(ByVal Exppression As String, ByRef Good As Boolean, ByRef Position As Integer, ByVal xxx As Double) As Double
        Dim Tmp As Double
        Dim isg As Boolean
        Tmp = NonopDigital(Exppression, isg, Position, xxx)
        If Not (isg) Then Tmp = g(Exppression, isg, Position, xxx)
        F2 = Tmp
        Good = isg
    End Function

Answer 6

Private Function g(ByVal Exppression As String, ByRef Good As Boolean, ByRef Position As Integer, ByVal xxx As Double) As Double
        Dim tmp1 As Double
        Dim tmp2 As Double
        Dim isg As Boolean
        Call PassBlank(Exppression, Position)
        If Match(Exppression, "SIN", Position) Then
            Position = Position + 3
            Call PassBlank(Exppression, Position)
            g = System.Math.Sin(G2(Exppression, Good, Position, xxx))
            Call PassBlank(Exppression, Position)
            Exit Function
        End If
        If Match(Exppression, "ABS", Position) Then
            Position = Position + 3
            Call PassBlank(Exppression, Position)
            g = System.Math.Abs(G2(Exppression, Good, Position, xxx))
            Call PassBlank(Exppression, Position)
            Exit Function
        End If
        If Match(Exppression, "CUB", Position) Then
            Position = Position + 3
            Call PassBlank(Exppression, Position)
            g = (G2(Exppression, Good, Position, xxx)) ^ (1 / 3)
            Call PassBlank(Exppression, Position)
            Exit Function
        End If
        If Match(Exppression, "SQR", Position) Then
            Position = Position + 3
            Call PassBlank(Exppression, Position)
            g = System.Math.Sqrt(G2(Exppression, Good, Position, xxx))
            Call PassBlank(Exppression, Position)
            Exit Function
        End If
        If Match(Exppression, "SGN", Position) Then
            Position = Position + 3
            Call PassBlank(Exppression, Position)
            g = System.Math.Sign(G2(Exppression, Good, Position, xxx))
            Call PassBlank(Exppression, Position)
            Exit Function
        End If
        If Match(Exppression, "RND", Position) Then
            Position = Position + 3
            Call PassBlank(Exppression, Position)
            g = Rnd() * G2(Exppression, Good, Position, xxx)
            Call PassBlank(Exppression, Position)
            Exit Function
        End If
        If Match(Exppression, "COS", Position) Then
            Position = Position + 3
            Call PassBlank(Exppression, Position)
            g = System.Math.Cos(G2(Exppression, Good, Position, xxx))
            Call PassBlank(Exppression, Position)
            Exit Function
        End If
        If Match(Exppression, "TAN", Position) Then
            Position = Position + 3
            Call PassBlank(Exppression, Position)
            g = System.Math.Tan(G2(Exppression, Good, Position, xxx))
            Call PassBlank(Exppression, Position)
            Exit Function
        End If
        If Match(Exppression, "LOG", Position) Then
            Position = Position + 3
            Call PassBlank(Exppression, Position)
            g = System.Math.Log(G2(Exppression, Good, Position, xxx)) / System.Math.Log(10.0#)
            Call PassBlank(Exppression, Position)
            Exit Function
        End If
        If Match(Exppression, "LN", Position) Then
            Position = Position + 2
            Call PassBlank(Exppression, Position)
            g = System.Math.Log(G2(Exppression, Good, Position, xxx))
            Call PassBlank(Exppression, Position)
            Exit Function
        End If
        If Match(Exppression, "EXP", Position) Then
            Position = Position + 3
            Call PassBlank(Exppression, Position)
            g = System.Math.Exp(G2(Exppression, Good, Position, xxx))
            Call PassBlank(Exppression, Position)
            Exit Function
        End If
        If Match(Exppression, "ARCTAN", Position) Then
            Position = Position + 6
            Call PassBlank(Exppression, Position)
            g = System.Math.Atan(G2(Exppression, Good, Position, xxx))
            Call PassBlank(Exppression, Position)
            Exit Function
        End If
        If Match(Exppression, "ARCSIN", Position) Then
            Position = Position + 6
            Call PassBlank(Exppression, Position)
            tmp1 = G2(Exppression, Good, Position, xxx)
            If tmp1 <> 1 And tmp1 <> -1 Then
                g = System.Math.Atan(tmp1 / System.Math.Sqrt(1 - tmp1 * tmp1))
            Else
                If tmp1 = 1 Then g = pi / 2 Else g = -pi / 2
            End If
            Call PassBlank(Exppression, Position)
            Exit Function
        End If
        If Match(Exppression, "ARCCOS", Position) Then
            Position = Position + 6
            Call PassBlank(Exppression, Position)
            tmp1 = G2(Exppression, Good, Position, xxx)
            If tmp1 <> 1 And tmp1 <> -1 Then
                g = System.Math.Atan(-tmp1 / System.Math.Sqrt(1 - tmp1 * tmp1)) + pi / 2
            Else
                If tmp1 = 1 Then g = 0.0# Else g = pi
            End If
            Call PassBlank(Exppression, Position)
            Exit Function
        End If
        If Match(Exppression, "POW", Position) Then
            Position = Position + 3
            Call PassBlank(Exppression, Position)
            If Match(Exppression, "(", Position) Then
                Position = Position + 1
                tmp1 = E(Exppression, isg, Position, xxx)
                If Match(Exppression, ",", Position) And isg Then
                    Position = Position + 1
                    tmp2 = E(Exppression, isg, Position, xxx)
                    If Match(Exppression, ")", Position) And isg Then
                        Position = Position + 1
                        Call PassBlank(Exppression, Position)
                        Good = True
                        g = tmp1 ^ tmp2
                        Exit Function
                    End If
                End If
            End If
            Good = False
            Exit Function
        End If
        g = G2(Exppression, Good, Position, xxx)
        Call PassBlank(Exppression, Position)
    End Function

Answer 7

Private Function G2(ByVal Exppression As String, ByRef Good As Boolean, ByRef Position As Integer, ByVal xxx As Double) As Double
        Dim Tmp As Double
        Dim isg As Boolean
        If Match(Exppression, "(", Position) Then
            Position = Position + 1
            Call PassBlank(Exppression, Position)
            Tmp = E(Exppression, isg, Position, xxx)
            If isg And Match(Exppression, ")", Position) Then
                G2 = Tmp
                Position = Position + 1
                Good = True
            Else
                Good = False
            End If
        End If
    End Function
    Private Function NonopDigital(ByVal Exppression As String, ByRef Good As Boolean, ByRef Position As Integer, ByVal xxx As Double) As Double
        Dim tmp1 As Double
        Dim tmp2 As Integer
        Dim tmpStr As String
        Call PassBlank(Exppression, Position)
        If Match(Exppression, "X", Position) Then
            NonopDigital = xxx
            Good = True
            Position = Position + 1
            Call PassBlank(Exppression, Position)
            Exit Function
        End If
        tmp1 = 0
        tmp2 = 0
        tmpStr = Mid(Exppression, Position, 1)
        If tmpStr >= "0" And tmpStr <= "9" Then
            While tmpStr >= "0" And tmpStr <= "9" Or tmpStr = " "
                tmp2 = tmp2 + 1
                tmpStr = Mid(Exppression, Position + tmp2, 1)
            End While
            If tmpStr = "." Then tmp2 = tmp2 + 1
            tmpStr = Mid(Exppression, Position + tmp2, 1)
            While tmpStr >= "0" And tmpStr <= "9" Or tmpStr = " "
                tmp2 = tmp2 + 1
                tmpStr = Mid(Exppression, Position + tmp2, 1)
            End While
            If tmpStr = "E" Then tmp2 = tmp2 + 1
            tmpStr = Mid(Exppression, Position + tmp2, 1)
            While tmpStr >= "0" And tmpStr <= "9" Or tmpStr = " "
                tmp2 = tmp2 + 1
                tmpStr = Mid(Exppression, Position + tmp2, 1)
            End While
            tmp1 = Val(Mid(Exppression, Position))
            Position = Position + tmp2
            Good = True
        Else
            Good = False
        End If
        NonopDigital = tmp1
    End Function
    Private Function OpDigital(ByVal Exppression As String, ByRef Good As Boolean, ByRef Position As Integer, ByVal xxx As Double) As Double
        Dim Tmp As Double
        Dim isg As Boolean
        Dim sign As Double
        sign = 1
        Call PassBlank(Exppression, Position)
        If Match(Exppression, "X", Position) Then
            OpDigital = xxx
            Good = True
            Position = Position + 1
            Call PassBlank(Exppression, Position)
            Exit Function
        End If
        If Match(Exppression, "-", Position) Then
            Position = Position + 1
            sign = -1
        Else
            If Match(Exppression, "+", Position) Or Mid(Exppression, Position, 1) >= "0" And Mid(Exppression, Position, 1) <= "9" Then
                sign = 1
            Else
                Good = False
                Exit Function
            End If
        End If
        Tmp = F2(Exppression, isg, Position, xxx)
        If Not (isg) Then Good = False Else Good = True
        OpDigital = Tmp * sign
    End Function
    Private Function Match(ByVal Exppression As String, ByVal Exppression2 As String, ByRef Position As Integer) As Boolean
        If Mid(Exppression, Position, Len(Exppression2)) = Exppression2 Then Match = True Else Match = False
    End Function
    Private Sub PassBlank(ByVal Exppression As String, ByRef Position As Integer)
        While Mid(Exppression, Position, 1) = " "
            Position = Position + 1
        End While
    End SubEnd Module

Answer 8

http://www.sooweb.net/Article/Programme/NET/1697.html