Double Structure
Assembly: mscorlib (in mscorlib.dll)
'Declaration <SerializableAttribute> _ <ComVisibleAttribute(True)> _ Public Structure Double Implements IComparable, IFormattable, IConvertible, IComparable(Of Double), _ IEquatable(Of Double) 'Usage Dim instance As Double
/** @attribute SerializableAttribute() */ /** @attribute ComVisibleAttribute(true) */ public final class Double extends ValueType implements IComparable, IFormattable, IConvertible, IComparable<double>, IEquatable<double>
JScript suports the use of structures, but not the declaration of new ones.
The Double value type represents a double-precision 64-bit number with values ranging from negative 1.79769313486232e308 to positive 1.79769313486232e308, as well as positive or negative zero, PositiveInfinity, NegativeInfinity, and Not-a-Number (NaN).
Double complies with the IEC 60559:1989 (IEEE 754) standard for binary floating-point arithmetic.
Double provides methods to compare instances of this type, convert the value of an instance to its string representation, and convert the string representation of a number to an instance of this type. For information about how format specification codes control the string representation of value types, see Formatting Overview, Standard Numeric Format Strings, and Custom Numeric Format Strings.
Using Floating-Point Numbers
When performing binary operations, if one of the operands is a Double, then the other operand is required to be an integral type or a floating-point type (Double or Single). Prior to performing the operation, if the other operand is not a Double, it is converted to Double, and the operation is performed using at least Double range and precision. If the operation produces a numeric result, the type of the result is Double.
The floating-point operators, including the assignment operators, do not throw exceptions. Instead, in exceptional situations the result of a floating-point operation is zero, infinity, or NaN, as described below:
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If the result of a floating-point operation is too small for the destination format, the result of the operation is zero.
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If the magnitude of the result of a floating-point operation is too large for the destination format, the result of the operation is PositiveInfinity or NegativeInfinity, as appropriate for the sign of the result.
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If a floating-point operation is invalid, the result of the operation is NaN.
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If one or both operands of a floating-point operation are NaN, the result of the operation is NaN.
Remember that a floating-point number can only approximate a decimal number, and that the precision of a floating-point number determines how accurately that number approximates a decimal number. By default, a Double value contains 15 decimal digits of precision, although a maximum of 17 digits is maintained internally. The precision of a floating-point number has several consequences:
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Two floating-point numbers that appear equal for a particular precision might not compare equal because their least significant digits are different.
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A mathematical or comparison operation that uses a floating-point number might not yield the same result if a decimal number is used because the floating-point number might not exactly approximate the decimal number.
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A value might not roundtrip if a floating-point number is involved. A value is said to roundtrip if an operation converts an original floating-point number to another form, an inverse operation transforms the converted form back to a floating-point number, and the final floating-point number is equal to the original floating-point number. The roundtrip might fail because one or more least significant digits are lost or changed in a conversion.
Interface Implementations
This type implements the interfaces IComparable, IComparable, IFormattable, and IConvertible. Use the Convert class for conversions instead of this type's explicit interface member implementation of IConvertible.
The following code example illustrates the use of Double:
' 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
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The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.