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FE_DOWNWARD, FE_TONEAREST, FE_TOWARDZERO, FE_UPWARD

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< cpp‎ | numeric‎ | fenv

 
 
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)
 
Defined in header <cfenv>
#define FE_DOWNWARD     /*implementation defined*/
(seit C++11)
#define FE_TONEAREST    /*implementation defined*/
(seit C++11)
#define FE_TOWARDZERO   /*implementation defined*/
(seit C++11)
#define FE_UPWARD       /*implementation defined*/
(seit C++11)
Jede dieser Makro-Konstanten weitet sich zu einer nichtnegativen Ganzzahlkonstantenausdruck, die mich mit verwendet std::fesetround und std::fegetround zu einem der unterstützten Floating-Point-Rundungsmodi anzuzeigen. Die Implementierung kann zusätzliche Rundungsmodus Konstanten in <cfenv> definieren, die alle sollten beginnen mit FE_ von mindestens einem Großbuchstaben gefolgt. Jedes Makro wird nur definiert, wenn sie unterstützt wird .
Original:
Each of these macro constants expands to a nonnegative integer constant expression, which can me used with std::fesetround and std::fegetround to indicate one of the supported floating-point rounding modes. The implementation may define additional rounding mode constants in <cfenv>, which should all begin with FE_ followed by at least one uppercase letter. Each macro is only defined if it is supported.
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Am meisten Implementierungen diese Makro-Konstanten mit den Werten gleich den Werten der FLT_ROUNDS und std::float_round_style erweitern
Original:
On most implementations, these macro constants expand to the values equal to the values of FLT_ROUNDS and std::float_round_style
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Constant
Original:
Constant
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Explanation
FE_DOWNWARD
Rundung in Richtung minus unendlich
Original:
rounding towards negative infinity
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FE_TONEAREST
Rundung zur nächsten ganzen Zahl
Original:
rounding towards nearest integer
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FE_TOWARDZERO
Rundung in Richtung Null
Original:
rounding towards zero
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FE_UPWARD
Rundung in Richtung plus unendlich
Original:
rounding towards positive infinity
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Zusätzliche Rundungsmodi kann durch eine Implementierung unterstützt werden .
Original:
Additional rounding modes may be supported by an implementation.
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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

zeigt Gleitkommazahl Rundungsmodi
Original:
indicates floating-point rounding modes
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(enum) [edit]
(C++11)
(C++11)
ab oder legt Rundung Richtung
Original:
gets or sets rounding direction
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(Funktion) [edit]