va_copy

 

C++

Sprache

Concepts

Utilities-Bibliothek

Strings Bibliothek

Container-Bibliothek

Algorithmen-Bibliothek

Iteratoren Bibliothek

Numerik-Bibliothek

Input / Output-Bibliothek

Lokalisierungen Bibliothek

Reguläre Ausdrücke Bibliothek (C++11)

Atomare Operationen Bibliothek (C++11)

Thread Support-Bibliothek (C++11)

 

Utilities-Bibliothek

Typen Unterstützung (basic types, RTTI, type traits)

Dynamische Speicherverwaltung

Fehlerbehandlung

Programm Unterstützung

Variadic Funktionen

Datum und Uhrzeit

Funktionsobjekte

initializer_list (C++11)

bitset

hash (C++11)

Relationale Operatoren

rel_ops::operator!= rel_ops::operator> rel_ops::operator<= rel_ops::operator>=

Paare und Tupel

pair

tuple (C++11)

piecewise_construct_t (C++11)

piecewise_construct (C++11)

Swap, forward und move

swap

forward (C++11)

move (C++11)

move_if_noexcept (C++11)

declval (C++11)

 

Variadic Funktionen

va_start

va_arg

va_copy

va_end

va_list

 

Defined in header <cstdarg>

void va_copy(va_list dest, va_list src);		(seit C++11)

Die va_copy Makro kopiert src um dest .

Original:

The va_copy macro copies src to dest.

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

va_end sollte auf dest bevor die Funktion zurückkehrt oder eine spätere Re-Initialisierung des dest aufgerufen werden (über Anrufe va_start oder va_copy) .

Original:

va_end should be called on dest before the function returns or any subsequent re-initialization of dest (via calls to va_start or va_copy).

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

Parameter

dest	-	eine Instanz der va_list geben zu initialisieren Original: an instance of the va_list type to initialize The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
src	-	die Quelle va_list, die verwendet werden, um dest initialisiert werden Original: the source va_list that will be used to initialize dest The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

Expanded Wert

(None)

Original:

(none)

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

Beispiel

#include <iostream>
#include <cstdarg>
#include <cmath>
 
double sample_stddev(int count, ...) 
{
    double sum = 0;
    va_list args1;
    va_start(args1, count);
    va_list args2;
    va_copy(args2, args1);
    for (int i = 0; i < count; ++i) {
        double num = va_arg(args1, double);
        sum += num;
    }
    double mean = sum / count;
 
    double sum_sq_diff = 0;
    for (int i = 0; i < count; ++i) {
        double num = va_arg(args2, double);
        sum_sq_diff += (num-mean) * (num-mean);
    }
    return std::sqrt(sum_sq_diff / count);
}
 
int main() 
{
    std::cout << sample_stddev(4, 25.0, 27.3, 26.9, 25.7) << '\n';
}

Output:

0.920258

Siehe auch

va_start	ermöglicht den Zugriff auf variadische Funktionsargumente Original: enables access to variadic function arguments The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (funktionieren Makro)
va_arg	greift auf die nächsten variadische Funktionsargument Original: accesses the next variadic function argument The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (funktionieren Makro)
va_end	endet Durchlaufen der variadische Funktionsargumente Original: ends traversal of the variadic function arguments The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (funktionieren Makro)