VB.NET Double结构体代码示例

' Temperature class stores the value as Double
' and delegates most of the functionality 
' to the Double implementation.
Public Class Temperature
    Implements IComparable, IFormattable

    Public Overloads Function CompareTo(ByVal obj As Object) As Integer _
        Implements IComparable.CompareTo

        If TypeOf obj Is Temperature Then
            Dim temp As Temperature = CType(obj, Temperature)

            Return m_value.CompareTo(temp.m_value)
        End If

        Throw New ArgumentException("object is not a Temperature")
    End Function

    Public Overloads Function ToString(ByVal format As String, ByVal provider As IFormatProvider) As String _
        Implements IFormattable.ToString

        If Not (format Is Nothing) Then
            If format.Equals("F") Then
                Return [String].Format("{0}'F", Me.Value.ToString())
            End If
            If format.Equals("C") Then
                Return [String].Format("{0}'C", Me.Celsius.ToString())
            End If
        End If

        Return m_value.ToString(format, provider)
    End Function

    ' Parses the temperature from a string in form
    ' [ws][sign]digits['F|'C][ws]
    Public Shared Function Parse(ByVal s As String, ByVal styles As NumberStyles, ByVal provider As IFormatProvider) As Temperature
        Dim temp As New Temperature()

        If s.TrimEnd(Nothing).EndsWith("'F") Then
            temp.Value = Double.Parse(s.Remove(s.LastIndexOf("'"c), 2), styles, provider)
        Else
            If s.TrimEnd(Nothing).EndsWith("'C") Then
                temp.Celsius = Double.Parse(s.Remove(s.LastIndexOf("'"c), 2), styles, provider)
            Else
                temp.Value = Double.Parse(s, styles, provider)
            End If
        End If
        Return temp
    End Function

    ' The value holder
    Protected m_value As Double

    Public Property Value() As Double
        Get
            Return m_value
        End Get
        Set(ByVal Value As Double)
            m_value = Value
        End Set
    End Property

    Public Property Celsius() As Double
        Get
            Return (m_value - 32) / 1.8
        End Get
        Set(ByVal Value As Double)
            m_value = Value * 1.8 + 32
        End Set
    End Property
End Class

Module Example
   Public Sub Main()
      Dim value As Double = .1
      Dim result1 As Double = value * 10
      Dim result2 As Double
      For ctr As Integer = 1 To 10
         result2 += value
      Next
      Console.WriteLine(".1 * 10:           {0:R}", result1)
      Console.WriteLine(".1 Added 10 times: {0:R}", result2)
   End Sub
End Module

Module Example
   Public Sub Main()
      Dim value As Double = 123456789012.34567
      Dim additional As Double = Double.Epsilon * 1e15
      Console.WriteLine("{0} + {1} = {2}", value, additional, 
                                           value + additional)
   End Sub
End Module

Module Example
   Public Sub Main()
      Dim values() As Double = { 10.0, 2.88, 2.88, 2.88, 9.0 }
      Dim result As Double = 27.64
      Dim total As Double
      For Each value In values
         total += value
      Next
      If total.Equals(result) Then
         Console.WriteLine("The sum of the values equals the total.")
      Else
         Console.WriteLine("The sum of the values ({0}) does not equal the total ({1}).",
                           total, result) 
      End If     
   End Sub
End Module

' 导入命名空间
Imports System.IO

Module Example
   Public Sub Main()
      Dim sw As New StreamWriter(".\Doubles.dat")
      Dim values() As Double = { 2.2/1.01, 1.0/3, Math.PI }
      For ctr As Integer = 0 To values.Length - 1
         sw.Write(values(ctr).ToString())
         If ctr <> values.Length - 1 Then sw.Write("|")
      Next      
      sw.Close()
      
      Dim restoredValues(values.Length - 1) As Double
      Dim sr As New StreamReader(".\Doubles.dat")
      Dim temp As String = sr.ReadToEnd()
      Dim tempStrings() As String = temp.Split("|"c)
      For ctr As Integer = 0 To tempStrings.Length - 1
         restoredValues(ctr) = Double.Parse(tempStrings(ctr))   
      Next 

      For ctr As Integer = 0 To values.Length - 1
         Console.WriteLine("{0} {2} {1}", values(ctr), 
                           restoredValues(ctr),
                           If(values(ctr).Equals(restoredValues(ctr)), "=", "<>"))
      Next
   End Sub
End Module

' 导入命名空间
Imports System.IO

Module Example
   Public Sub Main()
      Dim sw As New StreamWriter(".\Doubles.dat")
      Dim values() As Double = { 2.2/1.01, 1.0/3, Math.PI }
      For ctr As Integer = 0 To values.Length - 1
         sw.Write("{0:G17}{1}", values(ctr), 
                  If(ctr < values.Length - 1, "|", ""))
      Next      
      sw.Close()
      
      Dim restoredValues(values.Length - 1) As Double
      Dim sr As New StreamReader(".\Doubles.dat")
      Dim temp As String = sr.ReadToEnd()
      Dim tempStrings() As String = temp.Split("|"c)
      For ctr As Integer = 0 To tempStrings.Length - 1
         restoredValues(ctr) = Double.Parse(tempStrings(ctr))   
      Next 

      For ctr As Integer = 0 To values.Length - 1
         Console.WriteLine("{0} {2} {1}", values(ctr), 
                           restoredValues(ctr),
                           If(values(ctr).Equals(restoredValues(ctr)), "=", "<>"))
      Next
   End Sub
End Module

Module Example
   Public Sub Main()
      Dim value1 As Double = 1/3
      Dim sValue2 As Single = 1/3
      Dim value2 As Double = CDbl(sValue2)
      Console.WriteLine("{0} = {1}: {2}", value1, value2, value1.Equals(value2))
   End Sub
End Module

Dim value As Double = -4.42330604244772E-305

Dim fromLiteral As Double = -4.42330604244772E-305
Dim fromVariable As Double = value
Dim fromParse As Double = Double.Parse("-4.42330604244772E-305")

Console.WriteLine("Double value from literal: {0,29:R}", fromLiteral)
Console.WriteLine("Double value from variable: {0,28:R}", fromVariable)
Console.WriteLine("Double value from Parse method: {0,24:R}", fromParse)      
' On 32-bit versions of the .NET Framework, the output is:
'    Double value from literal:        -4.42330604244772E-305
'    Double value from variable:       -4.42330604244772E-305
'    Double value from Parse method:   -4.42330604244772E-305
'
' On other versions of the .NET Framework, the output is:
'    Double value from literal:        -4.4233060424477198E-305
'    Double value from variable:       -4.4233060424477198E-305
'    Double value from Parse method:     -4.42330604244772E-305

Module Example
   Public Sub Main()
      Dim value1 As Double = .333333333333333
      Dim value2 As Double = 1/3
      Console.WriteLine("{0:R} = {1:R}: {2}", value1, value2, value1.Equals(value2))
   End Sub
End Module

Module Example
   Public Sub Main()
      Dim value1 As Double = 100.10142
      value1 = Math.Sqrt(Math.Pow(value1, 2))
      Dim value2 As Double = Math.Pow(value1 * 3.51, 2)
      value2 = Math.Sqrt(value2) / 3.51
      Console.WriteLine("{0} = {1}: {2}", 
                        value1, value2, value1.Equals(value2)) 
      Console.WriteLine()
      Console.WriteLine("{0:R} = {1:R}", value1, value2) 
   End Sub
End Module

Module Example
   Public Sub Main()
      Dim value1 As Double = .333333333333333
      Dim value2 As Double = 1/3
      Dim precision As Integer = 7
      value1 = Math.Round(value1, precision)
      value2 = Math.Round(value2, precision)
      Console.WriteLine("{0:R} = {1:R}: {2}", value1, value2, value1.Equals(value2))
   End Sub
End Module

Module Example
   Public Sub Main()
      Dim one1 As Double = .1 * 10
      Dim one2 As Double = 0
      For ctr As Integer = 1 To 10
         one2 += .1
      Next
      Console.WriteLine("{0:R} = {1:R}: {2}", one1, one2, one1.Equals(one2))
      Console.WriteLine("{0:R} is approximately equal to {1:R}: {2}", 
                        one1, one2, 
                        IsApproximatelyEqual(one1, one2, .000000001))   
   End Sub

   Function IsApproximatelyEqual(value1 As Double, value2 As Double, 
                                 epsilon As Double) As Boolean
      ' If they are equal anyway, just return True.
      If value1.Equals(value2) Then Return True
      
      ' Handle NaN, Infinity.
      If Double.IsInfinity(value1) Or Double.IsNaN(value1) Then
         Return value1.Equals(value2)
      Else If Double.IsInfinity(value2) Or Double.IsNaN(value2)
         Return value1.Equals(value2)
      End If
      
      ' Handle zero to avoid division by zero
      Dim divisor As Double = Math.Max(value1, value2)
      If divisor.Equals(0) Then
         divisor = Math.Min(value1, value2)
      End If 
      
      Return Math.Abs((value1 - value2) / divisor) <= epsilon           
   End Function
End Module

Module Example
   Public Sub Main()
      Dim value1 As Double = 1.1632875981534209e-225
      Dim value2 As Double = 9.1642346778e-175
      Dim result As Double = value1 * value2
      Console.WriteLine("{0} * {1} = {2}", value1, value2, result)
      Console.WriteLine("{0} = 0: {1}", result, result.Equals(0.0))
   End Sub
End Module

Module Example
   Public Sub Main()
      Dim value1 As Double = 4.565e153
      Dim value2 As Double = 6.9375e172
      Dim result As Double = value1 * value2
      Console.WriteLine("PositiveInfinity: {0}", 
                         Double.IsPositiveInfinity(result))
      Console.WriteLine("NegativeInfinity: {0}", 
                        Double.IsNegativeInfinity(result))
      Console.WriteLine()                  
      value1 = -value1
      result = value1 * value2
      Console.WriteLine("PositiveInfinity: {0}", 
                         Double.IsPositiveInfinity(result))
      Console.WriteLine("NegativeInfinity: {0}", 
                        Double.IsNegativeInfinity(result))
   End Sub
End Module

Module Example
   Public Sub Main()
      Dim values() As Object = { Byte.MinValue, Byte.MaxValue, Decimal.MinValue,
                                 Decimal.MaxValue, Int16.MinValue, Int16.MaxValue,
                                 Int32.MinValue, Int32.MaxValue, Int64.MinValue,
                                 Int64.MaxValue, SByte.MinValue, SByte.MaxValue,
                                 Single.MinValue, Single.MaxValue, UInt16.MinValue,
                                 UInt16.MaxValue, UInt32.MinValue, UInt32.MaxValue,
                                 UInt64.MinValue, UInt64.MaxValue }
      Dim dblValue As Double
      For Each value In values
         dblValue = value
         Console.WriteLine("{0} ({1}) --> {2:R} ({3})",
                           value, value.GetType().Name,
                           dblValue, dblValue.GetType().Name)
      Next
   End Sub
End Module