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Estructura Double

 

Publicado: octubre de 2016

Representa un número de punto flotante de precisión doble.

Espacio de nombres:   System
Ensamblado:  mscorlib (en mscorlib.dll)

[SerializableAttribute]
[ComVisibleAttribute(true)]
public struct Double : IComparable, IFormattable, IConvertible, 
	IComparable<double>, IEquatable<double>

NombreDescripción
System_CAPS_pubmethodCompareTo(Double)

Compara esta instancia con un número de punto flotante de precisión doble especificado y devuelve un entero que indica si el valor de esta instancia es mayor, menor o igual que el valor del número de punto flotante de precisión doble especificado.

System_CAPS_pubmethodCompareTo(Object)

Compara esta instancia con un objeto especificado y devuelve un entero que indica si el valor de esta instancia es mayor, igual o menor que el valor del objeto especificado.

System_CAPS_pubmethodEquals(Double)

Devuelve un valor que indica si esta instancia y un objeto Double especificado representan el mismo valor.

System_CAPS_pubmethodEquals(Object)

Devuelve un valor que indica si esta instancia equivale a un objeto especificado.(Invalida ValueType.Equals(Object)).

System_CAPS_pubmethodGetHashCode()

Devuelve el código hash de esta instancia.(Invalida ValueType.GetHashCode()).

System_CAPS_pubmethodGetType()

Obtiene el Type de la instancia actual.(Heredado de Object).

System_CAPS_pubmethodGetTypeCode()

Devuelve el TypeCode para el tipo de valor Double.

System_CAPS_pubmethodSystem_CAPS_staticIsInfinity(Double)

Devuelve un valor que indica si el número especificado se evalúa como infinito negativo o positivo.

System_CAPS_pubmethodSystem_CAPS_staticIsNaN(Double)

Devuelve un valor que indica si el valor especificado no es un número (NaN).

System_CAPS_pubmethodSystem_CAPS_staticIsNegativeInfinity(Double)

Devuelve un valor que indica si el número especificado se evalúa como infinito negativo.

System_CAPS_pubmethodSystem_CAPS_staticIsPositiveInfinity(Double)

Devuelve un valor que indica si el número especificado se evalúa como infinito positivo.

System_CAPS_pubmethodSystem_CAPS_staticParse(String)

Convierte la representación en forma de cadena de un número en el número de punto flotante de precisión doble equivalente.

System_CAPS_pubmethodSystem_CAPS_staticParse(String, IFormatProvider)

Convierte la representación en forma de cadena de un número con un formato específico de la referencia cultural especificado en el número de punto flotante de precisión doble equivalente.

System_CAPS_pubmethodSystem_CAPS_staticParse(String, NumberStyles)

Convierte la representación en forma de cadena de un número con un estilo especificado en el número de punto flotante de precisión doble equivalente.

System_CAPS_pubmethodSystem_CAPS_staticParse(String, NumberStyles, IFormatProvider)

Convierte la representación en forma de cadena de un número con un estilo y un formato específico de la referencia cultural especificados en el número de punto flotante de precisión doble equivalente.

System_CAPS_pubmethodToString()

Convierte el valor numérico de esta instancia en la representación de cadena equivalente.(Invalida ValueType.ToString()).

System_CAPS_pubmethodToString(IFormatProvider)

Convierte el valor numérico de esta instancia en la representación de cadena equivalente usando la información de formato específica de la referencia cultural especificada.

System_CAPS_pubmethodToString(String)

Convierte el valor numérico de esta instancia en la representación de cadena equivalente usando el formato especificado.

System_CAPS_pubmethodToString(String, IFormatProvider)

Convierte el valor numérico de esta instancia en su representación de cadena equivalente mediante el formato y la información de formato específica de la referencia cultural que se especificaran.

System_CAPS_pubmethodSystem_CAPS_staticTryParse(String, Double)

Convierte la representación en forma de cadena de un número en el número de punto flotante de precisión doble equivalente. Un valor devuelto indica si la conversión se realizó correctamente o si se produjeron errores.

System_CAPS_pubmethodSystem_CAPS_staticTryParse(String, NumberStyles, IFormatProvider, Double)

Convierte la representación en forma de cadena de un número con un estilo y un formato específico de la referencia cultural especificados en el número de punto flotante de precisión doble equivalente. Un valor devuelto indica si la conversión se realizó correctamente o si se produjeron errores.

NombreDescripción
System_CAPS_pubfieldSystem_CAPS_staticEpsilon

Representa el menor valor Double positivo mayor que cero. Este campo es constante.

System_CAPS_pubfieldSystem_CAPS_staticMaxValue

Representa el mayor valor posible de un Double. Este campo es constante.

System_CAPS_pubfieldSystem_CAPS_staticMinValue

Representa el menor valor posible de un Double. Este campo es constante.

System_CAPS_pubfieldSystem_CAPS_staticNaN

Representa un valor no numérico (NaN). Este campo es constante.

System_CAPS_pubfieldSystem_CAPS_staticNegativeInfinity

Representa infinito negativo. Este campo es constante.

System_CAPS_pubfieldSystem_CAPS_staticPositiveInfinity

Representa infinito positivo. Este campo es constante.

NombreDescripción
System_CAPS_puboperatorSystem_CAPS_staticEquality(Double, Double)

Devuelve un valor que indica si dos valores Double especificados son iguales.

System_CAPS_puboperatorSystem_CAPS_staticGreaterThan(Double, Double)

Devuelve un valor que indica si un valor Double especificado es mayor que otro valor Double especificado.

System_CAPS_puboperatorSystem_CAPS_staticGreaterThanOrEqual(Double, Double)

Devuelve un valor que indica si un valor Double especificado es mayor o igual que otro valor Double especificado.

System_CAPS_puboperatorSystem_CAPS_staticInequality(Double, Double)

Devuelve un valor que indica si dos valores Double especificados no son iguales.

System_CAPS_puboperatorSystem_CAPS_staticLessThan(Double, Double)

Devuelve un valor que indica si un valor Double especificado es menor que otro valor Double especificado.

System_CAPS_puboperatorSystem_CAPS_staticLessThanOrEqual(Double, Double)

Devuelve un valor que indica si un valor Double especificado es menor o igual que otro valor Double especificado.

NombreDescripción
System_CAPS_pubinterfaceSystem_CAPS_privmethodIConvertible.ToBoolean(IFormatProvider)

Esta API admite la infraestructura producto y no está diseñada para usarse directamente desde el código. Para una descripción de este miembro, vea IConvertible.ToBoolean.

System_CAPS_pubinterfaceSystem_CAPS_privmethodIConvertible.ToByte(IFormatProvider)

Esta API admite la infraestructura producto y no está diseñada para usarse directamente desde el código. Para una descripción de este miembro, vea IConvertible.ToByte.

System_CAPS_pubinterfaceSystem_CAPS_privmethodIConvertible.ToChar(IFormatProvider)

Esta API admite la infraestructura producto y no está diseñada para usarse directamente desde el código. No se admite esta conversión. Cualquier intento de usar este método produce una excepción InvalidCastException.

System_CAPS_pubinterfaceSystem_CAPS_privmethodIConvertible.ToDateTime(IFormatProvider)

Esta API admite la infraestructura producto y no está diseñada para usarse directamente desde el código. No se admite esta conversión. Cualquier intento de usar este método produce una excepción InvalidCastException.

System_CAPS_pubinterfaceSystem_CAPS_privmethodIConvertible.ToDecimal(IFormatProvider)

Esta API admite la infraestructura producto y no está diseñada para usarse directamente desde el código. Para una descripción de este miembro, vea IConvertible.ToDecimal.

System_CAPS_pubinterfaceSystem_CAPS_privmethodIConvertible.ToDouble(IFormatProvider)

Esta API admite la infraestructura producto y no está diseñada para usarse directamente desde el código. Para una descripción de este miembro, vea IConvertible.ToDouble.

System_CAPS_pubinterfaceSystem_CAPS_privmethodIConvertible.ToInt16(IFormatProvider)

Esta API admite la infraestructura producto y no está diseñada para usarse directamente desde el código. Para una descripción de este miembro, vea IConvertible.ToInt16.

System_CAPS_pubinterfaceSystem_CAPS_privmethodIConvertible.ToInt32(IFormatProvider)

Esta API admite la infraestructura producto y no está diseñada para usarse directamente desde el código. Para una descripción de este miembro, vea IConvertible.ToInt32.

System_CAPS_pubinterfaceSystem_CAPS_privmethodIConvertible.ToInt64(IFormatProvider)

Esta API admite la infraestructura producto y no está diseñada para usarse directamente desde el código. Para una descripción de este miembro, vea IConvertible.ToInt64.

System_CAPS_pubinterfaceSystem_CAPS_privmethodIConvertible.ToSByte(IFormatProvider)

Esta API admite la infraestructura producto y no está diseñada para usarse directamente desde el código. Para una descripción de este miembro, vea IConvertible.ToSByte.

System_CAPS_pubinterfaceSystem_CAPS_privmethodIConvertible.ToSingle(IFormatProvider)

Esta API admite la infraestructura producto y no está diseñada para usarse directamente desde el código. Para una descripción de este miembro, vea IConvertible.ToSingle.

System_CAPS_pubinterfaceSystem_CAPS_privmethodIConvertible.ToType(Type, IFormatProvider)

Esta API admite la infraestructura producto y no está diseñada para usarse directamente desde el código. Para una descripción de este miembro, vea IConvertible.ToType.

System_CAPS_pubinterfaceSystem_CAPS_privmethodIConvertible.ToUInt16(IFormatProvider)

Esta API admite la infraestructura producto y no está diseñada para usarse directamente desde el código. Para una descripción de este miembro, vea IConvertible.ToUInt16.

System_CAPS_pubinterfaceSystem_CAPS_privmethodIConvertible.ToUInt32(IFormatProvider)

Esta API admite la infraestructura producto y no está diseñada para usarse directamente desde el código. Para una descripción de este miembro, vea IConvertible.ToUInt32.

System_CAPS_pubinterfaceSystem_CAPS_privmethodIConvertible.ToUInt64(IFormatProvider)

Esta API admite la infraestructura producto y no está diseñada para usarse directamente desde el código. Para una descripción de este miembro, vea IConvertible.ToUInt64.

The T:System.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, F:System.Double.PositiveInfinity, F:System.Double.NegativeInfinity, and not a number (F:System.Double.NaN). It is intended to represent values that are extremely large (such as distances between planets or galaxies) or extremely small (the molecular mass of a substance in kilograms) and that often are imprecise (such as the distance from earth to another solar system), The T:System.Double type complies with the IEC 60559:1989 (IEEE 754) standard for binary floating-point arithmetic.

This topic consists of the following sections:

The T:System.Double data type stores double-precision floating-point values in a 64-bit binary format, as shown in the following table:

Part

Bits

Significand or mantissa

0-51

Exponent

52-62

Sign (0 = Positive, 1 = Negative)

63

Just as decimal fractions are unable to precisely represent some fractional values (such as 1/3 or F:System.Math.PI), binary fractions are unable to represent some fractional values. For example, 1/10, which is represented precisely by .1 as a decimal fraction, is represented by .001100110011 as a binary fraction, with the pattern "0011" repeating to infinity. In this case, the floating-point value provides an imprecise representation of the number that it represents. Performing additional mathematical operations on the original floating-point value often tends to increase its lack of precision. For example, if we compare the result of multiplying .1 by 10 and adding .1 to .1 nine times, we see that addition, because it has involved eight more operations, has produced the less precise result. Note that this disparity is apparent only if we display the two T:System.Double values by using the "R" standard numeric format string, which if necessary displays all 17 digits of precision supported by the T:System.Double type.

using System;

public class Example
{
   public static void Main()
   {
      Double value = .1;
      Double result1 = value * 10;
      Double result2 = 0;
      for (int ctr = 1; ctr <= 10; ctr++)
         result2 += value;

      Console.WriteLine(".1 * 10:           {0:R}", result1);
      Console.WriteLine(".1 Added 10 times: {0:R}", result2);
   }
}
// The example displays the following output:
//       .1 * 10:           1
//       .1 Added 10 times: 0.99999999999999989

Because some numbers cannot be represented exactly as fractional binary values, floating-point numbers can only approximate real numbers.

All floating-point numbers also have a limited number of significant digits, which also determines how accurately a floating-point value approximates a real number. A T:System.Double value has up to 15 decimal digits of precision, although a maximum of 17 digits is maintained internally. This means that some floating-point operations may lack the precision to change a floating point value. The following example provides an illustration. It defines a very large floating-point value, and then adds the product of F:System.Double.Epsilon and one quadrillion to it. The product, however, is too small to modify the original floating-point value. Its least significant digit is thousandths, whereas the most significant digit in the product is 1-312.

using System;

public class Example
{
   public static void Main()
   {
      Double value = 123456789012.34567;
      Double additional = Double.Epsilon * 1e15;
      Console.WriteLine("{0} + {1} = {2}", value, additional, 
                                           value + additional);
   }
}
// The example displays the following output:
//    123456789012.346 + 4.94065645841247E-309 = 123456789012.346

The limited precision of a floating-point number has several consequences:

  • Two floating-point numbers that appear equal for a particular precision might not compare equal because their least significant digits are different. In the following example, a series of numbers are added together, and their total is compared with their expected total. Although the two values appear to be the same, a call to the Equals method indicates that they are not.

    using System;
    
    public class Example
    {
       public static void Main()
       {
          Double[] values = { 10.0, 2.88, 2.88, 2.88, 9.0 };
          Double result = 27.64;
          Double total = 0;
          foreach (var value in values)
             total += value;
    
          if (total.Equals(result))
             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); 
       }
    }
    // The example displays the following output:
    //      The sum of the values (36.64) does not equal the total (36.64).   
    //
    // If the index items in the Console.WriteLine statement are changed to {0:R},
    // the example displays the following output:
    //       The sum of the values (27.639999999999997) does not equal the total (27.64).   
    

    If you change the format items in the M:System.Console.WriteLine(System.String,System.Object,System.Object) statement from {0} and {1} to {0:R} and {1:R} to display all significant digits of the two T:System.Double values, it is clear that the two values are unequal because of a loss of precision during the addition operations. In this case, the issue can be resolved by calling the M:System.Math.Round(System.Double,System.Int32) method to round the T:System.Double values to the desired precision before performing the comparison.

  • 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 binary floating-point number might not equal the decimal number. A previous example illustrated this by displaying the result of multiplying .1 by 10 and adding .1 times.

    When accuracy in numeric operations with fractional values is important, you can use the T:System.Decimal rather than the T:System.Double type. When accuracy in numeric operations with integral values beyond the range of the T:System.Int64 or T:System.UInt64 types is important, use the T:System.Numerics.BigInteger type.

  • A value might not round-trip if a floating-point number is involved. A value is said to round-trip 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 not 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. In the following example, three T:System.Double values are converted to strings and saved in a file. As the output shows, however, even though the values appear to be identical, the restored values are not equal to the original values.

    using System;
    using System.IO;
    
    public class Example
    {
       public static void Main()
       {
          StreamWriter sw = new StreamWriter(@".\Doubles.dat");
          Double[] values = { 2.2/1.01, 1.0/3, Math.PI };
          for (int ctr = 0; ctr < values.Length; ctr++) {
             sw.Write(values[ctr].ToString());
             if (ctr != values.Length - 1)
                sw.Write("|");
          }      
          sw.Close();
    
          Double[] restoredValues = new Double[values.Length];
          StreamReader sr = new StreamReader(@".\Doubles.dat");
          string temp = sr.ReadToEnd();
          string[] tempStrings = temp.Split('|');
          for (int ctr = 0; ctr < tempStrings.Length; ctr++)
             restoredValues[ctr] = Double.Parse(tempStrings[ctr]);   
    
    
          for (int ctr = 0; ctr < values.Length; ctr++)
             Console.WriteLine("{0} {2} {1}", values[ctr], 
                               restoredValues[ctr],
                               values[ctr].Equals(restoredValues[ctr]) ? "=" : "<>");
       }
    }
    // The example displays the following output:
    //       2.17821782178218 <> 2.17821782178218
    //       0.333333333333333 <> 0.333333333333333
    //       3.14159265358979 <> 3.14159265358979
    

    In this case, the values can be successfully round-tripped by using the "R" standard numeric format string to preserve the full precision of T:System.Double values, as the following example shows.

    using System;
    using System.IO;
    
    public class Example
    {
       public static void Main()
       {
          StreamWriter sw = new StreamWriter(@".\Doubles.dat");
          Double[] values = { 2.2/1.01, 1.0/3, Math.PI };
          for (int ctr = 0; ctr < values.Length; ctr++) 
             sw.Write("{0:R}{1}", values[ctr], ctr < values.Length - 1 ? "|" : "" );
    
          sw.Close();
    
          Double[] restoredValues = new Double[values.Length];
          StreamReader sr = new StreamReader(@".\Doubles.dat");
          string temp = sr.ReadToEnd();
          string[] tempStrings = temp.Split('|');
          for (int ctr = 0; ctr < tempStrings.Length; ctr++)
             restoredValues[ctr] = Double.Parse(tempStrings[ctr]);   
    
    
          for (int ctr = 0; ctr < values.Length; ctr++)
             Console.WriteLine("{0} {2} {1}", values[ctr], 
                               restoredValues[ctr],
                               values[ctr].Equals(restoredValues[ctr]) ? "=" : "<>");
       }
    }
    // The example displays the following output:
    //       2.17821782178218 = 2.17821782178218
    //       0.333333333333333 = 0.333333333333333
    //       3.14159265358979 = 3.14159265358979
    
  • Single values have less precision than Double values. A Single value that is converted to a seemingly equivalent Double often does not equal the Double value because of differences in precision. In the following example, the result of identical division operations is assigned to a Double and a Single value. After the Single value is cast to a Double, a comparison of the two values shows that they are unequal.

    using System;
    
    public class Example
    {
       public static void Main()
       {
          Double value1 = 1/3.0;
          Single sValue2 = 1/3.0f;
          Double value2 = (Double) sValue2;
          Console.WriteLine("{0:R} = {1:R}: {2}", value1, value2, 
                                              value1.Equals(value2));
       }
    }
    // The example displays the following output:
    //        0.33333333333333331 = 0.3333333432674408: False
    

    To avoid this problem, use either the T:System.Double in place of the T:System.Single data type, or use the M:System.Math.Round(System.Double) method so that both values have the same precision.

In addition, the result of arithmetic and assignment operations with T:System.Double values may differ slightly by platform because of the loss of precision of the T:System.Double type. For example, the result of assigning a literal T:System.Double value may differ in the 32-bit and 64-bit versions of the .NET Framework. The following example illustrates this difference when the literal value -4.42330604244772E-305 and a variable whose value is -4.42330604244772E-305 are assigned to a T:System.Double variable. Note that the result of the M:System.Double.Parse(System.String) method in this case does not suffer from a loss of precision.

double value = -4.42330604244772E-305;

double fromLiteral = -4.42330604244772E-305;
double fromVariable = value;
double fromParse = 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      

To be considered equal, two T:System.Double values must represent identical values. However, because of differences in precision between values, or because of a loss of precision by one or both values, floating-point values that are expected to be identical often turn out to be unequal because of differences in their least significant digits. As a result, calls to the M:System.Double.Equals(System.Double) method to determine whether two values are equal, or calls to the M:System.Double.CompareTo(System.Double) method to determine the relationship between two T:System.Double values, often yield unexpected results. This is evident in the following example, where two apparently equal T:System.Double values turn out to be unequal because the first has 15 digits of precision, while the second has 17.

using System;

public class Example
{
   public static void Main()
   {
      double value1 = .333333333333333;
      double value2 = 1.0/3;
      Console.WriteLine("{0:R} = {1:R}: {2}", value1, value2, value1.Equals(value2));
   }
}
// The example displays the following output:
//        0.333333333333333 = 0.33333333333333331: False

Calculated values that follow different code paths and that are manipulated in different ways often prove to be unequal. In the following example, one T:System.Double value is squared, and then the square root is calculated to restore the original value. A second T:System.Double is multiplied by 3.51 and squared before the square root of the result is divided by 3.51 to restore the original value. Although the two values appear to be identical, a call to the M:System.Double.Equals(System.Double) method indicates that they are not equal. Using the "R" standard format string to return a result string that displays all the significant digits of each Double value shows that the second value is .0000000000001 less than the first.

using System;

public class Example
{
   public static void Main()
   {
      double value1 = 100.10142;
      value1 = Math.Sqrt(Math.Pow(value1, 2));
      double value2 = Math.Pow(value1 * 3.51, 2);
      value2 = Math.Sqrt(value2) / 3.51;
      Console.WriteLine("{0} = {1}: {2}\n", 
                        value1, value2, value1.Equals(value2)); 
      Console.WriteLine("{0:R} = {1:R}", value1, value2); 
   }
}
// The example displays the following output:
//    100.10142 = 100.10142: False
//    
//    100.10142 = 100.10141999999999

In cases where a loss of precision is likely to affect the result of a comparison, you can adopt any of the following alternatives to calling the M:System.Double.Equals(System.Double) or M:System.Double.CompareTo(System.Double) method:

  • Call the M:System.Math.Round(System.Double) method to ensure that both values have the same precision. The following example modifies a previous example to use this approach so that two fractional values are equivalent.

    using System;
    
    public class Example
    {
       public static void Main()
       {
          double value1 = .333333333333333;
          double value2 = 1.0/3;
          int precision = 7;
          value1 = Math.Round(value1, precision);
          value2 = Math.Round(value2, precision);
          Console.WriteLine("{0:R} = {1:R}: {2}", value1, value2, value1.Equals(value2));
       }
    }
    // The example displays the following output:
    //        0.3333333 = 0.3333333: True
    

    Note, though, that the problem of precision still applies to rounding of midpoint values. For more information, see the M:System.Math.Round(System.Double,System.Int32,System.MidpointRounding) method.

  • Test for approximate equality rather than equality. This requires that you define either an absolute amount by which the two values can differ but still be equal, or that you define a relative amount by which the smaller value can diverge from the larger value.

    System_CAPS_warningAdvertencia

    Double.Epsilon is sometimes used as an absolute measure of the distance between two Double values when testing for equality. However, Double.Epsilon measures the smallest possible value that can be added to, or subtracted from, a Double whose value is zero. For most positive and negative Double values, the value of Double.Epsilon is too small to be detected. Therefore, except for values that are zero, we do not recommend its use in tests for equality.

    The following example uses the latter approach to define an IsApproximatelyEqual method that tests the relative difference between two values. It also contrasts the result of calls to the IsApproximatelyEqual method and the M:System.Double.Equals(System.Double) method.

    using System;
    
    public class Example
    {
       public static void Main()
       {
          double one1 = .1 * 10;
          double one2 = 0;
          for (int ctr = 1; ctr <= 10; ctr++)
             one2 += .1;
    
          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));   
       }
    
       static bool IsApproximatelyEqual(double value1, double value2, double epsilon)
       {
          // If they are equal anyway, just return True.
          if (value1.Equals(value2))
             return true;
    
          // Handle NaN, Infinity.
          if (Double.IsInfinity(value1) | Double.IsNaN(value1))
             return value1.Equals(value2);
          else if (Double.IsInfinity(value2) | Double.IsNaN(value2))
             return value1.Equals(value2);
    
          // Handle zero to avoid division by zero
          double divisor = Math.Max(value1, value2);
          if (divisor.Equals(0)) 
             divisor = Math.Min(value1, value2);
    
          return Math.Abs(value1 - value2)/divisor <= epsilon;           
       } 
    }
    // The example displays the following output:
    //       1 = 0.99999999999999989: False
    //       1 is approximately equal to 0.99999999999999989: True
    

Unlike operations with integral types, which throw exceptions in cases of overflow or illegal operations such as division by zero, operations with floating-point values do not throw exceptions. Instead, in exceptional situations, the result of a floating-point operation is zero, positive infinity, negative infinity, or not a number (NaN):

  • If the result of a floating-point operation is too small for the destination format, the result is zero. This can occur when two very small numbers are multiplied, as the following example shows.

    using System;
    
    public class Example
    {
       public static void Main()
       {
          Double value1 = 1.1632875981534209e-225;
          Double value2 = 9.1642346778e-175;
          Double result = value1 * value2;
          Console.WriteLine("{0} * {1} = {2}", value1, value2, result);
          Console.WriteLine("{0} = 0: {1}", result, result.Equals(0.0));
       }
    }
    // The example displays the following output:
    //       1.16328759815342E-225 * 9.1642346778E-175 = 0
    //       0 = 0: True
    
  • If the magnitude of the result of a floating-point operation exceeds the range of the destination format, the result of the operation is F:System.Double.PositiveInfinity or F:System.Double.NegativeInfinity, as appropriate for the sign of the result. The result of an operation that overflows F:System.Double.MaxValue is F:System.Double.PositiveInfinity, and the result of an operation that overflows F:System.Double.MinValue is F:System.Double.NegativeInfinity, as the following example shows.

    using System;
    
    public class Example
    {
       public static void Main()
       {
          Double value1 = 4.565e153;
          Double value2 = 6.9375e172;
          Double result = value1 * value2;
          Console.WriteLine("PositiveInfinity: {0}", 
                             Double.IsPositiveInfinity(result));
          Console.WriteLine("NegativeInfinity: {0}\n", 
                            Double.IsNegativeInfinity(result));
    
          value1 = -value1;
          result = value1 * value2;
          Console.WriteLine("PositiveInfinity: {0}", 
                             Double.IsPositiveInfinity(result));
          Console.WriteLine("NegativeInfinity: {0}", 
                            Double.IsNegativeInfinity(result));
       }
    }                                                                 
    
    // The example displays the following output:
    //       PositiveInfinity: True
    //       NegativeInfinity: False
    //       
    //       PositiveInfinity: False
    //       NegativeInfinity: True
    

    PositiveInfinity also results from a division by zero with a positive dividend, and NegativeInfinity results from a division by zero with a negative dividend.

  • If a floating-point operation is invalid, the result of the operation is F:System.Double.NaN. For example, F:System.Double.NaN results from the following operations:

    • Division by zero with a dividend of zero. Note that other cases of division by zero result in either F:System.Double.PositiveInfinity or F:System.Double.NegativeInfinity.

  • Any floating-point operation with an invalid input. For example, calling the M:System.Math.Sqrt(System.Double) method with a negative value returns F:System.Double.NaN, as does calling the M:System.Math.Acos(System.Double) method with a value that is greater than one or less than negative one.

  • Any operation with an argument whose value is F:System.Double.NaN.

The T:System.Double structure does not define any explicit or implicit conversion operators; instead, conversions are implemented by the compiler.

The conversion of the value of any primitive numeric type to a T:System.Double is a widening conversion and therefore does not require an explicit cast operator or call to a conversion method unless a compiler explicitly requires it. For example, the C# compiler requires a casting operator for conversions from T:System.Decimal to T:System.Double, while the Visual Basic compiler does not. The following example converts the minimum or maximum value of other primitive numeric types to a T:System.Double.

using System;

public class Example
{
   public static void Main()
   {
      dynamic[] values = { 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 };
      double dblValue;
      foreach (var value in values) {
         if (value.GetType() == typeof(Decimal))
            dblValue = (Double) value;
         else
            dblValue = value;
         Console.WriteLine("{0} ({1}) --> {2:R} ({3})",
                           value, value.GetType().Name,
                           dblValue, dblValue.GetType().Name);
      }
   }
}
// The example displays the following output:
//    0 (Byte) --> 0 (Double)
//    255 (Byte) --> 255 (Double)
//    -79228162514264337593543950335 (Decimal) --> -7.9228162514264338E+28 (Double)
//    79228162514264337593543950335 (Decimal) --> 7.9228162514264338E+28 (Double)
//    -32768 (Int16) --> -32768 (Double)
//    32767 (Int16) --> 32767 (Double)
//    -2147483648 (Int32) --> -2147483648 (Double)
//    2147483647 (Int32) --> 2147483647 (Double)
//    -9223372036854775808 (Int64) --> -9.2233720368547758E+18 (Double)
//    9223372036854775807 (Int64) --> 9.2233720368547758E+18 (Double)
//    -128 (SByte) --> -128 (Double)
//    127 (SByte) --> 127 (Double)
//    -3.402823E+38 (Single) --> -3.4028234663852886E+38 (Double)
//    3.402823E+38 (Single) --> 3.4028234663852886E+38 (Double)
//    0 (UInt16) --> 0 (Double)
//    65535 (UInt16) --> 65535 (Double)
//    0 (UInt32) --> 0 (Double)
//    4294967295 (UInt32) --> 4294967295 (Double)
//    0 (UInt64) --> 0 (Double)
//    18446744073709551615 (UInt64) --> 1.8446744073709552E+19 (Double)

In addition, the T:System.Single values F:System.Single.NaN, F:System.Single.PositiveInfinity, and F:System.Single.NegativeInfinity covert to F:System.Double.NaN, F:System.Double.PositiveInfinity, and F:System.Double.NegativeInfinity, respectively.

Note that the conversion of the value of some numeric types to a T:System.Double value can involve a loss of precision. As the example illustrates, a loss of precision is possible when converting T:System.Decimal, T:System.Int64, T:System.Single, and T:System.UInt64 values to T:System.Double values.

The conversion of a T:System.Double value to a value of any other primitive numeric data type is a narrowing conversion and requires a cast operator (in C#), a conversion method (in Visual Basic), or a call to a T:System.Convert method. Values that are outside the range of the target data type, which are defined by the target type's MinValue and MaxValue properties, behave as shown in the following table.

Target type

Result

Any integral type

An T:System.OverflowException exception if the conversion occurs in a checked context.

If the conversion occurs in an unchecked context (the default in C#), the conversion operation succeeds but the value overflows.

Decimal

An T:System.OverflowException exception.

Single

Single.NegativeInfinity for negative values.

Single.PositiveInfinity for positive values.

In addition, F:System.Double.NaN, F:System.Double.PositiveInfinity, and F:System.Double.NegativeInfinity throw an T:System.OverflowException for conversions to integers in a checked context, but these values overflow when converted to integers in an unchecked context. For conversions to T:System.Decimal, they always throw an T:System.OverflowException. For conversions to T:System.Single, they convert to F:System.Single.NaN, F:System.Single.PositiveInfinity, and F:System.Single.NegativeInfinity, respectively.

Note that a loss of precision may result from converting a T:System.Double value to another numeric type. In the case of converting non-integral T:System.Double values, as the output from the example shows, the fractional component is lost when the T:System.Double value is either rounded (as in Visual Basic) or truncated (as in C#). For conversions to T:System.Decimal and T:System.Single values, the T:System.Double value may not have a precise representation in the target data type.

The following example converts a number of T:System.Double values to several other numeric types. The conversions occur in a checked context in Visual Basic (the default) and in C# (because of the checked keyword). The output from the example shows the result for conversions in both a checked an unchecked context. You can perform conversions in an unchecked context in Visual Basic by compiling with the /removeintchecks+ compiler switch and in C# by commenting out the checked statement.

using System;

public class Example
{
   public static void Main()
   {
      Double[] values = { Double.MinValue, -67890.1234, -12345.6789,
                          12345.6789, 67890.1234, Double.MaxValue,
                          Double.NaN, Double.PositiveInfinity,
                          Double.NegativeInfinity };
      checked {
         foreach (var value in values) {
            try {
                Int64 lValue = (long) value;
                Console.WriteLine("{0} ({1}) --> {2} (0x{2:X16}) ({3})",
                                  value, value.GetType().Name,
                                  lValue, lValue.GetType().Name);
            }
            catch (OverflowException) {
               Console.WriteLine("Unable to convert {0} to Int64.", value);
            }
            try {
                UInt64 ulValue = (ulong) value;
                Console.WriteLine("{0} ({1}) --> {2} (0x{2:X16}) ({3})",
                                  value, value.GetType().Name,
                                  ulValue, ulValue.GetType().Name);
            }
            catch (OverflowException) {
               Console.WriteLine("Unable to convert {0} to UInt64.", value);
            }
            try {
                Decimal dValue = (decimal) value;
                Console.WriteLine("{0} ({1}) --> {2} ({3})",
                                  value, value.GetType().Name,
                                  dValue, dValue.GetType().Name);
            }
            catch (OverflowException) {
               Console.WriteLine("Unable to convert {0} to Decimal.", value);
            }
            try {
                Single sValue = (float) value;
                Console.WriteLine("{0} ({1}) --> {2} ({3})",
                                  value, value.GetType().Name,
                                  sValue, sValue.GetType().Name);
            }
            catch (OverflowException) {
               Console.WriteLine("Unable to convert {0} to Single.", value);
            }
            Console.WriteLine();
         }
      }
   }
}
// The example displays the following output for conversions performed
// in a checked context:
//       Unable to convert -1.79769313486232E+308 to Int64.
//       Unable to convert -1.79769313486232E+308 to UInt64.
//       Unable to convert -1.79769313486232E+308 to Decimal.
//       -1.79769313486232E+308 (Double) --> -Infinity (Single)
//
//       -67890.1234 (Double) --> -67890 (0xFFFFFFFFFFFEF6CE) (Int64)
//       Unable to convert -67890.1234 to UInt64.
//       -67890.1234 (Double) --> -67890.1234 (Decimal)
//       -67890.1234 (Double) --> -67890.13 (Single)
//
//       -12345.6789 (Double) --> -12345 (0xFFFFFFFFFFFFCFC7) (Int64)
//       Unable to convert -12345.6789 to UInt64.
//       -12345.6789 (Double) --> -12345.6789 (Decimal)
//       -12345.6789 (Double) --> -12345.68 (Single)
//
//       12345.6789 (Double) --> 12345 (0x0000000000003039) (Int64)
//       12345.6789 (Double) --> 12345 (0x0000000000003039) (UInt64)
//       12345.6789 (Double) --> 12345.6789 (Decimal)
//       12345.6789 (Double) --> 12345.68 (Single)
//
//       67890.1234 (Double) --> 67890 (0x0000000000010932) (Int64)
//       67890.1234 (Double) --> 67890 (0x0000000000010932) (UInt64)
//       67890.1234 (Double) --> 67890.1234 (Decimal)
//       67890.1234 (Double) --> 67890.13 (Single)
//
//       Unable to convert 1.79769313486232E+308 to Int64.
//       Unable to convert 1.79769313486232E+308 to UInt64.
//       Unable to convert 1.79769313486232E+308 to Decimal.
//       1.79769313486232E+308 (Double) --> Infinity (Single)
//
//       Unable to convert NaN to Int64.
//       Unable to convert NaN to UInt64.
//       Unable to convert NaN to Decimal.
//       NaN (Double) --> NaN (Single)
//
//       Unable to convert Infinity to Int64.
//       Unable to convert Infinity to UInt64.
//       Unable to convert Infinity to Decimal.
//       Infinity (Double) --> Infinity (Single)
//
//       Unable to convert -Infinity to Int64.
//       Unable to convert -Infinity to UInt64.
//       Unable to convert -Infinity to Decimal.
//       -Infinity (Double) --> -Infinity (Single)
// The example displays the following output for conversions performed
// in an unchecked context:
//       -1.79769313486232E+308 (Double) --> -9223372036854775808 (0x8000000000000000) (Int64)
//       -1.79769313486232E+308 (Double) --> 9223372036854775808 (0x8000000000000000) (UInt64)
//       Unable to convert -1.79769313486232E+308 to Decimal.
//       -1.79769313486232E+308 (Double) --> -Infinity (Single)
//
//       -67890.1234 (Double) --> -67890 (0xFFFFFFFFFFFEF6CE) (Int64)
//       -67890.1234 (Double) --> 18446744073709483726 (0xFFFFFFFFFFFEF6CE) (UInt64)
//       -67890.1234 (Double) --> -67890.1234 (Decimal)
//       -67890.1234 (Double) --> -67890.13 (Single)
//
//       -12345.6789 (Double) --> -12345 (0xFFFFFFFFFFFFCFC7) (Int64)
//       -12345.6789 (Double) --> 18446744073709539271 (0xFFFFFFFFFFFFCFC7) (UInt64)
//       -12345.6789 (Double) --> -12345.6789 (Decimal)
//       -12345.6789 (Double) --> -12345.68 (Single)
//
//       12345.6789 (Double) --> 12345 (0x0000000000003039) (Int64)
//       12345.6789 (Double) --> 12345 (0x0000000000003039) (UInt64)
//       12345.6789 (Double) --> 12345.6789 (Decimal)
//       12345.6789 (Double) --> 12345.68 (Single)
//
//       67890.1234 (Double) --> 67890 (0x0000000000010932) (Int64)
//       67890.1234 (Double) --> 67890 (0x0000000000010932) (UInt64)
//       67890.1234 (Double) --> 67890.1234 (Decimal)
//       67890.1234 (Double) --> 67890.13 (Single)
//
//       1.79769313486232E+308 (Double) --> -9223372036854775808 (0x8000000000000000) (Int64)
//       1.79769313486232E+308 (Double) --> 0 (0x0000000000000000) (UInt64)
//       Unable to convert 1.79769313486232E+308 to Decimal.
//       1.79769313486232E+308 (Double) --> Infinity (Single)
//
//       NaN (Double) --> -9223372036854775808 (0x8000000000000000) (Int64)
//       NaN (Double) --> 0 (0x0000000000000000) (UInt64)
//       Unable to convert NaN to Decimal.
//       NaN (Double) --> NaN (Single)
//
//       Infinity (Double) --> -9223372036854775808 (0x8000000000000000) (Int64)
//       Infinity (Double) --> 0 (0x0000000000000000) (UInt64)
//       Unable to convert Infinity to Decimal.
//       Infinity (Double) --> Infinity (Single)
//
//       -Infinity (Double) --> -9223372036854775808 (0x8000000000000000) (Int64)
//       -Infinity (Double) --> 9223372036854775808 (0x8000000000000000) (UInt64)
//       Unable to convert -Infinity to Decimal.
//       -Infinity (Double) --> -Infinity (Single)

For more information on the conversion of numeric types, see Type Conversion in the .NET Framework and Type Conversion Tables in the .NET Framework.

The T:System.Double structure and related types provide methods to perform operations in the following areas:

  • Comparison of values. You can call the Equals method to determine whether two Double values are equal, or the CompareTo method to determine the relationship between two values.

    The T:System.Double structure also supports a complete set of comparison operators. For example, you can test for equality or inequality, or determine whether one value is greater than or equal to another. If one of the operands is a numeric type other than a T:System.Double, it is converted to a T:System.Double before performing the comparison.

    System_CAPS_warningAdvertencia

    Because of differences in precision, two T:System.Double values that you expect to be equal may turn out to be unequal, which affects the result of the comparison. See the Testing for Equality section for more information about comparing two T:System.Double values.

    You can also call the M:System.Double.IsNaN(System.Double), M:System.Double.IsInfinity(System.Double), M:System.Double.IsPositiveInfinity(System.Double), and M:System.Double.IsNegativeInfinity(System.Double) methods to test for these special values.

  • Mathematical operations. Common arithmetic operations, such as addition, subtraction, multiplication, and division, are implemented by language compilers and Common Intermediate Language (CIL) instructions, rather than by Double methods. If one of the operands in a mathematical operation is a numeric type other than a Double, it is converted to a Double before performing the operation. The result of the operation is also a Double value.

    Other mathematical operations can be performed by calling static (Shared in Visual Basic) methods in the T:System.Math class. It includes additional methods commonly used for arithmetic (such as M:System.Math.Abs(System.Double), M:System.Math.Sign(System.Double), and M:System.Math.Sqrt(System.Double)), geometry (such as M:System.Math.Cos(System.Double) and M:System.Math.Sin(System.Double)), and calculus (such as M:System.Math.Log(System.Double)).

    You can also manipulate the individual bits in a T:System.Double value. The M:System.BitConverter.DoubleToInt64Bits(System.Double) method preserves a T:System.Double value's bit pattern in a 64-bit integer. The M:System.BitConverter.GetBytes(System.Double) method returns its bit pattern in a byte array.

  • Rounding. Rounding is often used as a technique for reducing the impact of differences between values caused by problems of floating-point representation and precision. You can round a Double value by calling the Math.Round method.

  • Formatting. You can convert a Double value to its string representation by calling the ToString method or by using the composite formatting feature. For information about how format strings control the string representation of floating-point values, see the Cadenas con formato numérico estándar and Cadenas con formato numérico personalizado topics.

  • Parsing strings. You can convert the string representation of a floating-point value to a Double value by calling either the Parse or TryParse method. If the parse operation fails, the Parse method throws an exception, whereas the TryParse method returns false.

  • Type conversion. The Double structure provides an explicit interface implementation for the IConvertible interface, which supports conversion between any two standard .NET Framework data types. Language compilers also support the implicit conversion of values of all other standard numeric types to Double values. Conversion of a value of any standard numeric type to a Double is a widening conversion and does not require the user of a casting operator or conversion method,

    However, conversion of T:System.Int64 and T:System.Single values can involve a loss of precision. The following table lists the differences in precision for each of these types:

    Type

    Maximum precision

    Internal precision

    Double

    15

    17

    Int64

    19 decimal digits

    19 decimal digits

    Single

    7 decimal digits

    9 decimal digits

    The problem of precision most frequently affects T:System.Single values that are converted to T:System.Double values. In the following example, two values produced by identical division operations are unequal because one of the values is a a single-precision floating point value converted to a T:System.Double.

    using System;
    
    public class Example
    {
       public static void Main()
       {
          Double value = .1;
          Double result1 = value * 10;
          Double result2 = 0;
          for (int ctr = 1; ctr <= 10; ctr++)
             result2 += value;
    
          Console.WriteLine(".1 * 10:           {0:R}", result1);
          Console.WriteLine(".1 Added 10 times: {0:R}", result2);
       }
    }
    // The example displays the following output:
    //       .1 * 10:           1
    //       .1 Added 10 times: 0.99999999999999989
    

The following code example illustrates the use of T:System.Double:

// The Temperature class stores the temperature as a Double
// and delegates most of the functionality to the Double
// implementation.
public class Temperature : IComparable, IFormattable 
   {
	// IComparable.CompareTo implementation.
	public int CompareTo(object obj) {
           if (obj == null) return 1;

		Temperature temp = obj as Temperature;
           if (obj != null) 
			return m_value.CompareTo(temp.m_value);
		else
    			throw new ArgumentException("object is not a Temperature");	
	}

	// IFormattable.ToString implementation.
	public string ToString(string format, IFormatProvider provider) {
		if( format != null ) {
			if( format.Equals("F") ) {
				return String.Format("{0}'F", this.Value.ToString());
			}
			if( format.Equals("C") ) {
				return String.Format("{0}'C", this.Celsius.ToString());
			}
		}

		return m_value.ToString(format, provider);
	}

	// Parses the temperature from a string in the form
	// [ws][sign]digits['F|'C][ws]
	public static Temperature Parse(string s, NumberStyles styles, IFormatProvider provider) {
		Temperature temp = new Temperature();

		if( s.TrimEnd(null).EndsWith("'F") ) {
			temp.Value = Double.Parse( s.Remove(s.LastIndexOf('\''), 2), styles, provider);
		}
		else if( s.TrimEnd(null).EndsWith("'C") ) {
			temp.Celsius = Double.Parse( s.Remove(s.LastIndexOf('\''), 2), styles, provider);
		}
		else {
			temp.Value = Double.Parse(s, styles, provider);
		}

		return temp;
	}

	// The value holder
	protected double m_value;

	public double Value {
		get {
			return m_value;
		}
		set {
			m_value = value;
		}
	}

	public double Celsius {
		get {
			return (m_value-32.0)/1.8;
		}
		set {
			m_value = 1.8*value+32.0;
		}
	}
}

Plataforma universal de Windows
Disponible desde 8
.NET Framework
Disponible desde 1.1
Biblioteca de clases portable
Se admite en: plataformas portátiles de .NET
Silverlight
Disponible desde 2.0
Windows Phone Silverlight
Disponible desde 7.0
Windows Phone
Disponible desde 8.1

All members of this type are thread safe. Members that appear to modify instance state actually return a new instance initialized with the new value. As with any other type, reading and writing to a shared variable that contains an instance of this type must be protected by a lock to guarantee thread safety.

System_CAPS_cautionPrecaución

Assigning an instance of this type is not thread safe on all hardware platforms because the binary representation of that instance might be too large to assign in a single atomic operation.

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