Namespace
Varianti

FE_DOWNWARD, FE_TONEAREST, FE_TOWARDZERO, FE_UPWARD

Da cppreference.com.
< cpp‎ | numeric‎ | fenv

 
 
Numeri libreria
Comuni funzioni matematiche
Virgola mobile ambiente
I numeri complessi
Array numerici
Pseudo-casuale generazione
In fase di compilazione aritmetica razionale (C++11)
Generici operazioni numeriche
Original:
Generic numeric operations
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iota(C++11)
accumulate
inner_product
adjacent_difference
partial_sum
 
Virgola mobile ambiente
Funzioni
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 costanti
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*/
(dal C++11)
#define FE_TONEAREST    /*implementation defined*/
(dal C++11)
#define FE_TOWARDZERO   /*implementation defined*/
(dal C++11)
#define FE_UPWARD       /*implementation defined*/
(dal C++11)
Ciascuna di queste costanti macro restituisce un negativo espressione intero costante, che può utilizzare con me std::fesetround e std::fegetround per indicare uno dei supportate virgola mobile modalità di arrotondamento. L'applicazione può definire ulteriori costanti modalità di arrotondamento nel <cfenv>, che dovrebbero iniziare con FE_ seguita da almeno una lettera maiuscola. Ogni macro è definito solo se supportato.
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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Sulla maggior parte delle implementazioni, queste costanti macro espandere i valori uguali ai valori di FLT_ROUNDS e std::float_round_style
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
arrotondamento verso l'infinito negativo
Original:
rounding towards negative infinity
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FE_TONEAREST
arrotondamento verso l'intero più vicino
Original:
rounding towards nearest integer
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FE_TOWARDZERO
arrotondamento verso lo zero
Original:
rounding towards zero
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FE_UPWARD
arrotondamento verso l'infinito positivo
Original:
rounding towards positive infinity
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Ulteriori modalità di arrotondamento può essere supportato da una implementazione.
Original:
Additional rounding modes may be supported by an implementation.
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[modifica] Esempio

[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

[modifica] Vedi anche

indica virgola mobile modalità di arrotondamento
Original:
indicates floating-point rounding modes
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(enum) [edit]
(C++11)
(C++11)
ottiene o imposta la direzione di arrotondamento
Original:
gets or sets rounding direction
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(funzione) [edit]