Math.Round Method (Double)
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Updated: May 2010
Rounds a double-precision floating-point value to the nearest integral value.
Namespace: System
Assembly: mscorlib (in mscorlib.dll)
Syntax
'Declaration
<SecuritySafeCriticalAttribute> _
Public Shared Function Round ( _
a As Double _
) As Double
[SecuritySafeCriticalAttribute]
public static double Round(
double a
)
Parameters
- a
Type: System.Double
A double-precision floating-point number to be rounded.
Return Value
Type: System.Double
The integer nearest a. If the fractional component of a is halfway between two integers, one of which is even and the other odd, then the even number is returned. Note that the method returns a Double type rather than an integral type.
Remarks
The behavior of this method follows IEEE Standard 754, section 4. This kind of rounding is sometimes called rounding to nearest, or banker's rounding. It minimizes rounding errors that result from consistently rounding a midpoint value in a single direction.
Notes to Callers
Because of the loss of precision that can result from representing decimal values as floating-point numbers or performing arithmetic operations on floating-point values, in some cases the Round(Double) method may not appear to round midpoint values to the nearest even integer. In the following example, because the floating-point value .1 has no finite binary representation, the first call to the Round(Double) method with a value of 11.5 returns 11 instead of 12.
Examples
The following example demonstrates rounding to nearest integer value.
Module Example
Public Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
outputBlock.Text &= "Classic Math.Round in Visual Basic" & vbCrLf
outputBlock.Text &= Math.Round(4.4) & vbCrLf ' 4
outputBlock.Text &= Math.Round(4.5) & vbCrLf ' 4
outputBlock.Text &= Math.Round(4.6) & vbCrLf ' 5
outputBlock.Text &= Math.Round(5.5) & vbCrLf ' 6
End Sub
End Module
using System;
class Example
{
public static void Demo(System.Windows.Controls.TextBlock outputBlock)
{
outputBlock.Text += "Classic Math.Round in CSharp" + "\n";
outputBlock.Text += Math.Round(4.4) + "\n"; // 4
outputBlock.Text += Math.Round(4.5) + "\n"; // 4
outputBlock.Text += Math.Round(4.6) + "\n"; // 5
outputBlock.Text += Math.Round(5.5) + "\n"; // 6
}
}
The following code sample uses Round to assist in the computation of the inner angles of a given trapezoid.
'The following class represents simple functionality of the trapezoid.
Class Example
Private m_longBase As Double
Private m_shortBase As Double
Private m_leftLeg As Double
Private m_rightLeg As Double
Public Sub New(ByVal longbase As Double, ByVal shortbase As Double, ByVal leftLeg As Double, ByVal rightLeg As Double)
m_longBase = Math.Abs(longbase)
m_shortBase = Math.Abs(shortbase)
m_leftLeg = Math.Abs(leftLeg)
m_rightLeg = Math.Abs(rightLeg)
End Sub
Private Function GetRightSmallBase() As Double
GetRightSmallBase = (Math.Pow(m_rightLeg, 2) - Math.Pow(m_leftLeg, 2) + Math.Pow(m_longBase, 2) + Math.Pow(m_shortBase, 2) - 2 * m_shortBase * m_longBase) / (2 * (m_longBase - m_shortBase))
End Function
Public Function GetHeight() As Double
Dim x As Double = GetRightSmallBase()
GetHeight = Math.Sqrt(Math.Pow(m_rightLeg, 2) - Math.Pow(x, 2))
End Function
Public Function GetSquare() As Double
GetSquare = GetHeight() * m_longBase / 2
End Function
Public Function GetLeftBaseRadianAngle() As Double
Dim sinX As Double = GetHeight() / m_leftLeg
GetLeftBaseRadianAngle = Math.Round(Math.Asin(sinX), 2)
End Function
Public Function GetRightBaseRadianAngle() As Double
Dim x As Double = GetRightSmallBase()
Dim cosX As Double = (Math.Pow(m_rightLeg, 2) + Math.Pow(x, 2) - Math.Pow(GetHeight(), 2)) / (2 * x * m_rightLeg)
GetRightBaseRadianAngle = Math.Round(Math.Acos(cosX), 2)
End Function
Public Function GetLeftBaseDegreeAngle() As Double
Dim x As Double = GetLeftBaseRadianAngle() * 180 / Math.PI
GetLeftBaseDegreeAngle = Math.Round(x, 2)
End Function
Public Function GetRightBaseDegreeAngle() As Double
Dim x As Double = GetRightBaseRadianAngle() * 180 / Math.PI
GetRightBaseDegreeAngle = Math.Round(x, 2)
End Function
Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
Dim trpz As Example = New Example(20, 10, 8, 6)
outputBlock.Text += String.Format("The trapezoid's bases are 20.0 and 10.0, the trapezoid's legs are 8.0 and 6.0") & vbCrLf
Dim h As Double = trpz.GetHeight()
outputBlock.Text &= "Trapezoid height is: " + h.ToString() & vbCrLf
Dim dxR As Double = trpz.GetLeftBaseRadianAngle()
outputBlock.Text &= "Trapezoid left base angle is: " + dxR.ToString() + " Radians" & vbCrLf
Dim dyR As Double = trpz.GetRightBaseRadianAngle()
outputBlock.Text &= "Trapezoid right base angle is: " + dyR.ToString() + " Radians" & vbCrLf
Dim dxD As Double = trpz.GetLeftBaseDegreeAngle()
outputBlock.Text &= "Trapezoid left base angle is: " + dxD.ToString() + " Degrees" & vbCrLf
Dim dyD As Double = trpz.GetRightBaseDegreeAngle()
outputBlock.Text &= "Trapezoid left base angle is: " + dyD.ToString() + " Degrees" & vbCrLf
End Sub
End Class
/// <summary>
/// The following class represents simple functionality of the trapezoid.
/// </summary>
class Example
{
private double m_longBase;
private double m_shortBase;
private double m_leftLeg;
private double m_rightLeg;
public Example(double longbase, double shortbase, double leftLeg, double rightLeg)
{
m_longBase = Math.Abs(longbase);
m_shortBase = Math.Abs(shortbase);
m_leftLeg = Math.Abs(leftLeg);
m_rightLeg = Math.Abs(rightLeg);
}
private double GetRightSmallBase()
{
return (Math.Pow(m_rightLeg, 2.0) - Math.Pow(m_leftLeg, 2.0) + Math.Pow(m_longBase, 2.0) + Math.Pow(m_shortBase, 2.0) - 2 * m_shortBase * m_longBase) / (2 * (m_longBase - m_shortBase));
}
public double GetHeight()
{
double x = GetRightSmallBase();
return Math.Sqrt(Math.Pow(m_rightLeg, 2.0) - Math.Pow(x, 2.0));
}
public double GetSquare()
{
return GetHeight() * m_longBase / 2.0;
}
public double GetLeftBaseRadianAngle()
{
double sinX = GetHeight() / m_leftLeg;
return Math.Round(Math.Asin(sinX), 2);
}
public double GetRightBaseRadianAngle()
{
double x = GetRightSmallBase();
double cosX = (Math.Pow(m_rightLeg, 2.0) + Math.Pow(x, 2.0) - Math.Pow(GetHeight(), 2.0)) / (2 * x * m_rightLeg);
return Math.Round(Math.Acos(cosX), 2);
}
public double GetLeftBaseDegreeAngle()
{
double x = GetLeftBaseRadianAngle() * 180 / Math.PI;
return Math.Round(x, 2);
}
public double GetRightBaseDegreeAngle()
{
double x = GetRightBaseRadianAngle() * 180 / Math.PI;
return Math.Round(x, 2);
}
public static void Demo(System.Windows.Controls.TextBlock outputBlock)
{
Example trpz = new Example(20.0, 10.0, 8.0, 6.0);
outputBlock.Text += String.Format("The trapezoid's bases are 20.0 and 10.0, the trapezoid's legs are 8.0 and 6.0") + "\n";
double h = trpz.GetHeight();
outputBlock.Text += "Trapezoid height is: " + h.ToString() + "\n";
double dxR = trpz.GetLeftBaseRadianAngle();
outputBlock.Text += "Trapezoid left base angle is: " + dxR.ToString() + " Radians" + "\n";
double dyR = trpz.GetRightBaseRadianAngle();
outputBlock.Text += "Trapezoid right base angle is: " + dyR.ToString() + " Radians" + "\n";
double dxD = trpz.GetLeftBaseDegreeAngle();
outputBlock.Text += "Trapezoid left base angle is: " + dxD.ToString() + " Degrees" + "\n";
double dyD = trpz.GetRightBaseDegreeAngle();
outputBlock.Text += "Trapezoid left base angle is: " + dyD.ToString() + " Degrees" + "\n";
}
}
Version Information
Silverlight
Supported in: 5, 4, 3
Silverlight for Windows Phone
Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0
XNA Framework
Supported in: Xbox 360, Windows Phone OS 7.0
Platforms
For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.
Change History
Date |
History |
Reason |
|---|---|---|
May 2010 |
Added the Notes for Callers section. |
Customer feedback. |