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FE_DFL_ENV

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>
#define FE_DFL_ENV  /*implementation defined*/
(depuis C++11)
Le FE_DFL_ENV macro constante développe en une expression de const std::fenv_t* type, qui pointe vers une copie complète de la valeur par défaut en virgule flottante environnement, qui est, de l'environnement tel qu'il est chargé au démarrage du programme .
Original:
The macro constant FE_DFL_ENV expands to an expression of type const std::fenv_t*, which points to a full copy of the default floating-point environment, that is, the environment as loaded at program startup.
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Macros complémentaires qui commencent par FE_ suivie par des lettres majuscules, et le const std::fenv_t* nature, peuvent être pris en charge par une mise en œuvre .
Original:
Additional macros that begin with FE_ followed by uppercase letters, and have the type const std::fenv_t*, may be supported by an implementation.
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[modifier] Exemple

#include <iostream>
#include <cfenv>
 
#pragma STDC FENV_ACCESS ON
 
void show_env()
{
    int e = std::fetestexcept(FE_ALL_EXCEPT);
    if(e & FE_DIVBYZERO) std::cout << "division by zero is raised\n";
    if(e & FE_INEXACT)   std::cout << "inexact is raised\n";
    if(e & FE_INVALID)   std::cout << "invalid is raised\n";
    if(e & FE_UNDERFLOW) std::cout << "underflow is raised\n";
    if(e & FE_OVERFLOW)  std::cout << "overflow is raised\n";
    int r = std::fegetround();
    switch(r)
    {  
        case FE_DOWNWARD: std::cout << "rounding down\n"; break;
        case FE_TONEAREST: std::cout << "rounding to nearest\n"; break;
        case FE_TOWARDZERO: std::cout << "rounding to zero\n"; break;
        case FE_UPWARD: std::cout << "rounding up\n"; break;
    }
}
 
int main()
{
    std::cout << "On startup: \n";
    show_env();
 
    std::feraiseexcept(FE_UNDERFLOW | FE_OVERFLOW);
    std::fesetround(FE_UPWARD);
 
    std::cout << "\nBefore restoration: \n";
    show_env();
 
    std::fesetenv(FE_DFL_ENV);
 
    std::cout << "\nAfter reset to default: \n";
    show_env();
}

Résultat :

On startup: 
rounding to nearest
 
Before restoration: 
underflow is raised
overflow is raised
rounding up
 
After reset to default: 
rounding to nearest

[modifier] Voir aussi

sauvegarde ou restaure l'environnement actuel point flottant
Original:
saves or restores the current floating point environment
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(fonction) [edit]
(C++11)
restaure l'environnement en virgule flottante et soulève le lever des exceptions précédemment
Original:
restores the floating-point environment and raises the previously raise exceptions
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(fonction) [edit]