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Double.CompareTo Method (Double)

Compares this instance to a specified double-precision floating-point number and returns an integer that indicates whether the value of this instance is less than, equal to, or greater than the value of the specified double-precision floating-point number.

Namespace:  System
Assembly:  mscorlib (in mscorlib.dll)

'Declaration
Public Function CompareTo ( _
	value As Double _
) As Integer

Parameters

value
Type: System.Double

A double-precision floating-point number to compare.

Return Value

Type: System.Int32
A signed number indicating the relative values of this instance and value.

Return Value

Description

Less than zero

This instance is less than value.

-or-

This instance is not a number (NaN) and value is a number.

Zero

This instance is equal to value.

-or-

Both this instance and value are not a number (NaN), PositiveInfinity, or NegativeInfinity.

Greater than zero

This instance is greater than value.

-or-

This instance is a number and value is not a number (NaN).

Implements

IComparable(Of T).CompareTo(T)

Values must be identical to be considered equal. Particularly when floating-point values depend on multiple mathematical operations, it is common for them to lose precision and for their values to be nearly identical except for their least significant digits. Because of this, the return value of the CompareTo method at times may seem surprising. For example, multiplication by a particular value followed by division by the same value should produce the original value. In the following example, however, the computed value turns out to be greater than the original value. Showing all significant digits of the two values by using the "R" standard numeric format string indicates that the computed value differs from the original value in its least significant digits. For information on handling such comparisons, see the Remarks section of the Equals(Double) method.

Module Example
   Public Sub Main()
       Dim value1 As Double = 6.185
       Dim value2 As Double = value1 * .1 / .1
       Console.WriteLine("Comparing {0} and {1}: {2}",
                         value1, value2, value1.CompareTo(value2))
       Console.WriteLine()
       Console.WriteLine("Comparing {0:R} and {1:R}: {2}",
                         value1, value2, value1.CompareTo(value2))
   End Sub 
End Module 
' The example displays the following output: 
'       Comparing 6.185 and 6.185: -1 
'        
'       Comparing 6.185 and 6.1850000000000005: -1

This method implements the System.IComparable(Of T) interface and performs slightly better than the Double.CompareTo method because it does not have to convert the value parameter to an object.

Note that, although an object whose value is NaN is not considered equal to another object whose value is NaN (even itself), the IComparable(Of T) interface requires that A.CompareTo(A) return zero.

Widening Conversions

Depending on your programming language, it might be possible to code a CompareTo method where the parameter type has fewer bits (is narrower) than the instance type. This is possible because some programming languages perform an implicit widening conversion that represents the parameter as a type with as many bits as the instance.

For example, suppose the instance type is Double and the parameter type is Int32. The Microsoft C# compiler generates instructions to represent the value of the parameter as a Double object, then generates a Double.CompareTo(Double) method that compares the values of the instance and the widened representation of the parameter.

Consult your programming language's documentation to determine if its compiler performs implicit widening conversions of numeric types. For more information, see the Type Conversion Tables topic.

Precision in Comparisons

The precision of floating-point numbers beyond the documented precision is specific to the implementation and version of the .NET Framework. Consequently, a comparison of two particular numbers might change between versions of the .NET Framework because the precision of the numbers' internal representation might change.

The following code example demonstrates generic and nongeneric versions of the CompareTo method for several value and reference types.

' This example demonstrates the generic and non-generic versions of the  
' CompareTo method for several base types. 
' The non-generic version takes a parameter of type Object, while the generic 
' version takes a type-specific parameter, such as Boolean, Int32, or Double. 

Imports System

Class Sample
   Public Shared Sub Main()
      Dim nl As String = Environment.NewLine
      Dim msg As String = _
          "{0}The following is the result of using the generic and non-generic{0}" & _
          "versions of the CompareTo method for several base types:{0}" 

      Dim now As DateTime = DateTime.Now
      ' Time span = 11 days, 22 hours, 33 minutes, 44 seconds 
      Dim tsX As New TimeSpan(11, 22, 33, 44)
      ' Version = 1.2.333.4 
      Dim versX As New Version("1.2.333.4")
      ' Guid = CA761232-ED42-11CE-BACD-00AA0057B223 
      Dim guidX As New Guid("{CA761232-ED42-11CE-BACD-00AA0057B223}")

      Dim a1 As [Boolean] = True,    a2 As [Boolean] = True 
      Dim b1 As [Byte] = 1,          b2 As [Byte] = 1
      Dim c1 As Int16 = -2,          c2 As Int16 = 2
      Dim d1 As Int32 = 3,           d2 As Int32 = 3
      Dim e1 As Int64 = 4,           e2 As Int64 = -4
      Dim f1 As [Decimal] = -5.5D,   f2 As [Decimal] = 5.5D
      Dim g1 As [Single] = 6.6F,     g2 As [Single] = 6.6F
      Dim h1 As [Double] = 7.7,      h2 As [Double] = -7.7
      Dim i1 As [Char] = "A"c,       i2 As [Char] = "A"c
      Dim j1 As String = "abc",      j2 As String = "abc" 
      Dim k1 As DateTime = now,      k2 As DateTime = now
      Dim l1 As TimeSpan = tsX,      l2 As TimeSpan = tsX
      Dim m1 As Version = versX,     m2 As New Version("2.0")
      Dim n1 As Guid = guidX,        n2 As Guid = guidX

      ' The following types are not CLS-compliant. 
      ' SByte, UInt16, UInt32, UInt64

      Console.WriteLine(msg, nl)
      Try 
         ' The second and third Show method call parameters are automatically boxed because 
         ' the second and third Show method declaration arguments expect type Object.

         Show("Boolean:  ", a1, a2, a1.CompareTo(a2), a1.CompareTo(CObj(a2)))
         Show("Byte:     ", b1, b2, b1.CompareTo(b2), b1.CompareTo(CObj(b2)))
         Show("Int16:    ", c1, c2, c1.CompareTo(c2), c1.CompareTo(CObj(c2)))
         Show("Int32:    ", d1, d2, d1.CompareTo(d2), d1.CompareTo(CObj(d2)))
         Show("Int64:    ", e1, e2, e1.CompareTo(e2), e1.CompareTo(CObj(e2)))
         Show("Decimal:  ", f1, f2, f1.CompareTo(f2), f1.CompareTo(CObj(f2)))
         Show("Single:   ", g1, g2, g1.CompareTo(g2), g1.CompareTo(CObj(g2)))
         Show("Double:   ", h1, h2, h1.CompareTo(h2), h1.CompareTo(CObj(h2)))
         Show("Char:     ", i1, i2, i1.CompareTo(i2), i1.CompareTo(CObj(i2)))
         Show("String:   ", j1, j2, j1.CompareTo(j2), j1.CompareTo(CObj(j2)))
         Show("DateTime: ", k1, k2, k1.CompareTo(k2), k1.CompareTo(CObj(k2)))
         Show("TimeSpan: ", l1, l2, l1.CompareTo(l2), l1.CompareTo(CObj(l2)))
         Show("Version:  ", m1, m2, m1.CompareTo(m2), m1.CompareTo(CObj(m2)))
         Show("Guid:     ", n1, n2, n1.CompareTo(n2), n1.CompareTo(CObj(n2)))
         '
         Console.WriteLine("{0}The following types are not CLS-compliant:", nl)
         Console.WriteLine("SByte, UInt16, UInt32, UInt64")

      Catch e As Exception
         Console.WriteLine(e)
      End Try 
   End Sub 'Main

   Public Shared Sub Show(caption As String, var1 As [Object], var2 As [Object], _
                          resultGeneric As Integer, resultNonGeneric As Integer)
      Dim relation As String

      Console.Write(caption)
      If resultGeneric = resultNonGeneric Then 
         If resultGeneric < 0 Then
            relation = "less than" 
         ElseIf resultGeneric > 0 Then
            relation = "greater than" 
         Else
            relation = "equal to" 
         End If
         Console.WriteLine("{0} is {1} {2}", var1, relation, var2)

      ' The following condition will never occur because the generic and non-generic 
      ' CompareTo methods are equivalent. 

      Else
         Console.WriteLine("Generic CompareTo = {0}; non-generic CompareTo = {1}", _
                            resultGeneric, resultNonGeneric)
      End If 
   End Sub 'Show
End Class 'Sample

'This example produces the following results: 

'The following is the result of using the generic and non-generic versions of the 
'CompareTo method for several base types: 

'Boolean:  True is equal to True 
'Byte:     1 is equal to 1 
'Int16:    -2 is less than 2 
'Int32:    3 is equal to 3 
'Int64:    4 is greater than -4 
'Decimal:  -5.5 is less than 5.5 
'Single:   6.6 is equal to 6.6 
'Double:   7.7 is greater than -7.7 
'Char:     A is equal to A 
'String:   abc is equal to abc 
'DateTime: 12/1/2003 5:37:46 PM is equal to 12/1/2003 5:37:46 PM 
'TimeSpan: 11.22:33:44 is equal to 11.22:33:44 
'Version:  1.2.333.4 is less than 2.0 
'Guid:     ca761232-ed42-11ce-bacd-00aa0057b223 is equal to ca761232-ed42-11ce-bacd-00 
'aa0057b223 

'The following types are not CLS-compliant: 
'SByte, UInt16, UInt32, UInt64 
'

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

.NET for Windows Store apps

Supported in: Windows 8

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone 8, Silverlight 8.1

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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