Variadic functions
From cppreference.com
C++
Utilities library
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Variadic functions are functions (e.g. std::printf) which take a variable number of arguments
To declare a variadic function, an ellipsis appears after the list of parameters, e.g. int printf( const char * format...) ; , which may be preceded by an optional comma. See Variadic arguments
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) |
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| accesses the next variadic function argument (function macro) |
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(C++11)
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makes a copy of the variadic function arguments (function macro) |
| ends traversal of the variadic function arguments (function macro) |
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| holds the information needed by va_start, va_arg, va_end, and va_copy
(typedef) |
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Example
Run this code
#include <cstdarg> #include <iostream> void simple_printf(const char* fmt...) // C-style "const char* fmt, ..." is also valid { 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
See also
C documentation for Variadic functions
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