va_copy - cppreference.com (original) (raw)
| | | | | ------------------------------------------------------- | | ------------- | | void va_copy( std::va_list dest, std::va_list src ); | | (since C++11) |
The va_copy macro copies src to dest.
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).
[edit] Parameters
| dest | - | an instance of the va_list type to initialize |
|---|---|---|
| src | - | the source va_list that will be used to initialize dest |
[edit] Expanded value
(none)
[edit] Example
#include #include #include double sample_stddev(int count, ...) { double sum = 0; std::va_list args1; va_start(args1, count); std::va_list args2; va_copy(args2, args1); for (int i = 0; i < count; ++i) { double num = va_arg(args1, double); sum += num; } va_end(args1); 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); } va_end(args2); return std::sqrt(sum_sq_diff / count); } int main() { std::cout << sample_stddev(4, 25.0, 27.3, 26.9, 25.7) << '\n'; }
Output: