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std::fegetround, std::fesetround

De cppreference.com
< cpp‎ | numeric‎ | fenv

 
 
Bibliothèque Numerics
Fonctions mathématiques courantes
Virgule flottante environnement
Nombres complexes
Tableaux numériques
La génération de nombres pseudo-aléatoires
Moment de la compilation arithmétique rationnelle (C++11)
Génériques des opérations numériques
Original:
Generic numeric operations
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iota (C++11)
accumulate
inner_product
adjacent_difference
partial_sum
 
Virgule flottante environnement
Fonctions
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)
Macro constantes
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>
int fesetround( int round )
(1) (depuis C++11)
int fegetround()
(2) (depuis C++11)
1)
Tentatives pour établir la direction d'arrondi en virgule flottante égale à la round argument, qui devrait être l'un des macros flottant arrondi de points .
Original:
Attempts to establish the floating-point rounding direction equal to the argument round, which is expected to be one of the macros flottant arrondi de points.
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2)
Retourne la valeur de la flotter macro arrondi point qui correspond à la direction d'approximation courante .
Original:
Returns the value of the flotter macro arrondi point that corresponds to the current rounding direction.
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Sommaire

[modifier] Paramètres

round -
direction arrondissement, l'un des macros flottant arrondi de points
Original:
rounding direction, one of macros flottant arrondi de points
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[modifier] Retourne la valeur

1)
0 en cas de succès, non nuls autrement .
Original:
0 on success, non-zero otherwise.
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2)
l'flotter macro arrondi point décrivant la direction d'approximation courante ou une valeur négative si la direction ne peut pas être déterminée
Original:
the flotter macro arrondi point describing the current rounding direction or a negative value if the direction cannot be determined
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[modifier] Exemple

[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';
}

Résultat :

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

[modifier] Voir aussi

(C++11)
entier le plus proche en utilisant le mode d'arrondi courant
Original:
nearest integer using current rounding mode
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(fonction) [edit]
(C++11)
(C++11)
(C++11)
entier le plus proche en utilisant le mode d'arrondi courant à l'exception
si le résultat est différent
Original:
nearest integer using current rounding mode with
exception if the result differs
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(fonction) [edit]