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std::fegetround, std::fesetround

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C++
 
Numerik-Bibliothek
Gemeinsame mathematischen Funktionen
Floating-Point-Umgebung
Komplexe Zahlen
Numerische Arrays
Pseudo-Zufallszahlen
Compile-time rationale Arithmetik (C++11)
Generische numerische Operationen
Original:
Generic numeric operations
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iota(C++11)
accumulate
inner_product
adjacent_difference
partial_sum
 
Floating-Point-Umgebung
Funktionen
Original:
Functions
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feclearexcept(C++11)
fetestexcept(C++11)
feraiseexcept(C++11)
fegetexceptflag
fesetexceptflag		(C++11)
(C++11)
fegetround
fesetround		(C++11)
(C++11)
fegetenv
fesetenv		(C++11)
feholdexcept(C++11)
feupdateenv(C++11)
Makro Konstanten
Original:
Macro constants
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FE_ALL_EXCEPT
FE_DIVBYZERO
FE_INEXACT
FE_INVALID
FE_OVERFLOW
FE_UNDERFLOW		(C++11)
FE_DOWNWARD
FE_TONEAREST
FE_TOWARDZERO
FE_UPWARD		(C++11)
FE_DFL_ENV(C++11)
 
definiert in Header <cfenv>
int fesetround( int round )
 (1) (seit C++11)
int fegetround()
 (2) (seit C++11)
1)
Versuche, die Floating-Point-Rundung Richtung gleich dem Argument round, die voraussichtlich zu einem der Gleitkomma-Rundung Makros sein wird zu etablieren .
Original:
Attempts to establish the floating-point rounding direction equal to the argument round, which is expected to be one of the Gleitkomma-Rundung Makros.
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2)
Gibt den Wert des Gleitkomma-Rundung Makro, die dem aktuellen Rundung Richtung entspricht .
Original:
Returns the value of the Gleitkomma-Rundung Makro that corresponds to the current rounding direction.
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Inhaltsverzeichnis

[Bearbeiten] Parameter

round -
Rundung Richtung einer Gleitkomma-Rundung Makros
Original:
rounding direction, one of Gleitkomma-Rundung Makros
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[Bearbeiten] Rückgabewert

1)
​0​ bei Erfolg Null sonst .
Original:
​0​ on success, non-zero otherwise.
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2)
die Gleitkomma-Rundung Makro die den aktuellen Rundungsrichtung oder einen negativen Wert, wenn die Richtung, nicht ermittelt werden
Original:
the Gleitkomma-Rundung Makro describing the current rounding direction or a negative value if the direction cannot be determined
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[Bearbeiten] Beispiel

[edit]
#include <cmath>
#include <cfenv>
#include <iostream>
 
int main()
{
    #pragma STDC FENV_ACCESS ON
    std::fesetround(FE_DOWNWARD);
    std::cout << "rounding using FE_DOWNWARD: \n" << std::fixed
              << " 12.0 ->  " << std::nearbyint(12.0) << '\n'
              << " 12.1 ->  " << std::nearbyint(12.1) << '\n'
              << "-12.1 -> " << std::nearbyint(-12.1) << '\n'
              << " 12.5 ->  " << std::nearbyint(12.5) << '\n'
              << " 12.9 ->  " << std::nearbyint(12.9) << '\n'
              << "-12.9 -> " << std::nearbyint(-12.9) << '\n'
              << " 13.0 ->  " << std::nearbyint(13.0) << '\n';
    std::fesetround(FE_TONEAREST);
    std::cout << "rounding using FE_TONEAREST: \n"
              << " 12.0 ->  " << std::nearbyint(12.0) << '\n'
              << " 12.1 ->  " << std::nearbyint(12.1) << '\n'
              << "-12.1 -> " << std::nearbyint(-12.1) << '\n'
              << " 12.5 ->  " << std::nearbyint(12.5) << '\n'
              << " 12.9 ->  " << std::nearbyint(12.9) << '\n'
              << "-12.9 -> " << std::nearbyint(-12.9) << '\n'
              << " 13.0 ->  " << std::nearbyint(13.0) << '\n';
}

Output: 

rounding using FE_DOWNWARD:
 12.0 ->  12.000000
 12.1 ->  12.000000
-12.1 -> -13.000000
 12.5 ->  12.000000
 12.9 ->  12.000000
-12.9 -> -13.000000
 13.0 ->  13.000000
rounding using FE_TONEAREST: 
 12.0 ->  12.000000
 12.1 ->  12.000000
-12.1 -> -12.000000
 12.5 ->  12.000000
 12.9 ->  13.000000
-12.9 -> -13.000000
 13.0 ->  13.000000

[Bearbeiten] Siehe auch

(C++11)
nächste ganze Zahl mit aktuellen Rundung Modus
Original:
nearest integer using current rounding mode
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(Funktion) [edit]
(C++11)
(C++11)
(C++11)
nächste ganze Zahl mit aktuellen Rundung Modus mit
Ausnahme, wenn das Ergebnis unterscheidet
Original:
nearest integer using current rounding mode with
exception if the result differs
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(Funktion) [edit]
Von „https://de.cppreference.com/mwiki/index.php?title=cpp/numeric/fenv/feround&oldid=29484“