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std::numeric_limits::quiet_NaN

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C++
 
Utilities-Bibliothek
 
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Basic types
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Feste Breite Integer-Typen (C++11)
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numeric_limits
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std::numeric_limits
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static T quiet_NaN()
 (bis C + +11)
static constexpr T quiet_NaN()
 (seit C++11)
Gibt den besonderen Wert "quiet not-a-number", wie von der Fließkomma-Typ T vertreten. Nur sinnvoll, wenn std::numeric_limits<T>::has_quiet_NaN == true. In IEEE 754, die häufigste Binärdarstellung Gleitkommazahlen, repräsentiert jeder Wert mit allen Bits des Exponenten eingestellten und mindestens ein Bit des Satzes einen Bruchteil NaN. Es wird durch die Implementierung definiert, welche Werte der Fraktion ruhig oder singaling NaNs darstellen, und ob das Vorzeichenbit ist sinnvoll .
Original:
Returns the special value "quiet not-a-number", as represented by the floating-point type T. Only meaningful if std::numeric_limits<T>::has_quiet_NaN == true. In IEEE 754, the most common binary representation of floating-point numbers, any value with all bits of the exponent set and at least one bit of the fraction set represents a NaN. It is implementation-defined which values of the fraction represent quiet or singaling NaNs, and whether the sign bit is meaningful.
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Inhaltsverzeichnis

[Bearbeiten] Rückgabewert

T std::numeric_limits<T>::quiet_NaN()
/* non-specialized */ T();
bool false
char ​0​
signed char ​0​
unsigned char ​0​
wchar_t ​0​
char16_t ​0​
char32_t ​0​
short ​0​
unsigned short ​0​
int ​0​
unsigned int ​0​
long ​0​
unsigned long ​0​
long long ​0​
unsigned long long ​0​
float
NAN oder eine andere Implementierung definiert NaN
Original:
NAN or another implementation-defined NaN
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double
Implementierung definiert
Original:
implementation-defined
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long double
Implementierung definiert
Original:
implementation-defined
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[Bearbeiten] Ausnahmen

noexcept specification:  
noexcept
  (seit C++11)

[Bearbeiten] Notes

Ein NaN nie vergleicht sich selbst gleich. Kopieren einer NaN kann nicht bewahren ihre Bit-Darstellung .
Original:
A NaN never compares equal to itself. Copying a NaN may not preserve its bit representation.
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[Bearbeiten] Beispiel

Mehrere Möglichkeiten, um ein NaN (die Ausgabe-String ist Compiler-spezifisch) zu generieren
Original:
Several ways to generate a NaN (the output string is compiler-specific)
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#include <iostream>
#include <limits>
#include <cmath>
int main()
{
    std::cout << std::numeric_limits<double>::quiet_NaN() << ' '
              << std::numeric_limits<double>::signaling_NaN() << ' '
              << std::acos(2) << ' '
              << std::tgamma(-1) << ' '
              << std::log(-1) << ' '
              << std::sqrt(-1) << ' '
              << 0 / 0.0 << '\n';
 
    std::cout << "NaN == NaN? " << std::boolalpha
              << ( std::numeric_limits<double>::quiet_NaN()
                   == std::numeric_limits<double>::quiet_NaN() ) << '\n';
}

Output: 

nan nan nan nan nan -nan -nan
NaN == NaN? false

[Bearbeiten] Siehe auch

[statisch]
identifiziert Floating-Point-Typen, die den besonderen Wert "quiet not-a-number" (NaN) darstellen kann
Original:
identifies floating-point types that can represent the special value "quiet not-a-number" (NaN)
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(public static Mitglied konstanten) [edit]
[statisch]
gibt ein Signal NaN Wert der gegebenen Fließkomma-Typ
Original:
returns a signaling NaN value of the given floating-point type
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(public static Elementfunktion) [edit]
Von „https://de.cppreference.com/mwiki/index.php?title=cpp/types/numeric_limits/quiet_NaN&oldid=30326“