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std::fegetround, std::fesetround

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>
int fesetround( int round )
(1) (dal C++11)
int fegetround()
(2) (dal C++11)
1)
I tentativi di stabilire in virgola mobile direzione arrotondamento pari al round argomento, che dovrebbe essere uno dei galleggiante macro arrotondamento punto.
Original:
Attempts to establish the floating-point rounding direction equal to the argument round, which is expected to be one of the galleggiante macro arrotondamento punto.
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2)
Restituisce il valore della galleggiante arrotondamento macro punto che corrisponde alla direzione di arrotondamento corrente.
Original:
Returns the value of the galleggiante arrotondamento macro punto that corresponds to the current rounding direction.
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Indice

[modifica] Parametri

round -
arrotondamento direzione, uno dei galleggiante macro arrotondamento punto
Original:
rounding direction, one of galleggiante macro arrotondamento punto
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[modifica] Valore di ritorno

1)
0 in caso di successo, non-zero altrimenti.
Original:
0 on success, non-zero otherwise.
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2)
la galleggiante arrotondamento macro punto descrive la direzione corrente arrotondamento o un valore negativo se la direzione non può essere determinata
Original:
the galleggiante arrotondamento macro punto describing the current rounding direction or a negative value if the direction cannot be determined
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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

(C++11)
numero intero più vicino utilizzando la modalità corrente di arrotondamento
Original:
nearest integer using current rounding mode
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(funzione) [edit]
(C++11)
(C++11)
(C++11)
numero intero più vicino utilizzando la modalità corrente di arrotondamento ad eccezione
se il risultato è diverso
Original:
nearest integer using current rounding mode with
exception if the result differs
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(funzione) [edit]