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Variadic functions

From cppreference.com
< cpp‎ | utility

Variadic functions are functions (e.g. std::printf) which take a variable number of arguments.

To declare a variadic function, an ellipsis is used as the last parameter, e.g. int printf(const char* format, ...);. See Variadic arguments for additional detail on the syntax, automatic argument conversions and the alternatives.

To access the variadic arguments from the function body, the following library facilities are provided:

Defined in header <cstdarg>
enables access to variadic function arguments
(function macro) [edit]
accesses the next variadic function argument
(function macro) [edit]
(C++11)
makes a copy of the variadic function arguments
(function macro) [edit]
ends traversal of the variadic function arguments
(function macro) [edit]
holds the information needed by va_start, va_arg, va_end, and va_copy
(class) [edit]

[edit] Example

#include <iostream>
#include <cstdarg>
 
void simple_printf(const char* fmt...)
{
    va_list args;
    va_start(args, fmt);
 
    while (*fmt != '\0') {
        if (*fmt == 'd') {
            int i = va_arg(args, int);
            std::cout << i << '\n';
        } else if (*fmt == 'c') {
            // note automatic conversion to integral type
            int c = va_arg(args, int);
            std::cout << static_cast<char>(c) << '\n';
        } else if (*fmt == 'f') {
            double d = va_arg(args, double);
            std::cout << d << '\n';
        }
        ++fmt;
    }
 
    va_end(args);
}
 
int main()
{
    simple_printf("dcff", 3, 'a', 1.999, 42.5); 
}

Output:

3
a
1.999
42.5

[edit] See also

C documentation for Variadic functions