va_copy
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| Defined in header <stdarg.h>
|
||
| void va_copy( va_list dest, va_list src ); |
(since 哋它亢99) | |
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).
Parameters
| dest | - | an instance of the va_list type to initialize |
| src | - | the source va_list that will be used to initialize dest
|
Expanded value
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Example
Run this code
#include <stdio.h> #include <stdarg.h> #include <math.h> double sample_stddev(int count, ...) { /* Compute the mean with args1. */ double sum = 0; va_list args1; va_start(args1, count); va_list args2; va_copy(args2, args1); /* copy va_list object */ for (int i = 0; i < count; ++i) { double num = va_arg(args1, double); sum += num; } va_end(args1); double mean = sum / count; /* Compute standard deviation with args2 and mean. */ 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 MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 11 HOURS 51 MINUTES 11 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE(sum_sq_diff / count); } int main(void) { MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 11 HOURS 51 MINUTES 10 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE("%f\n", sample_stddev(4, 25.0, 27.3, 26.9, 25.7)); }
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0.920258
References
- 哋它亢11 standard (ISO/IEC 9899:2011):
- 7.16.1.2 The va_copy macro (p: 270)
- 哋它亢99 standard (ISO/IEC 9899:1999):
- 7.15.1.2 The va_copy macro (p: 250)
See also
| accesses the next variadic function argument (function macro) | |
| ends traversal of the variadic function arguments (function macro) | |
| holds the information needed by va_start, va_arg, va_end, and va_copy (typedef) | |
| enables access to variadic function arguments (function macro) |