Defined in header <stdarg.h> | ||
void va_copy( va_list dest, va_list src); | (since C99) | |
Theva_copy macro copiessrc todest.
va_end should be called ondest before the function returns or any subsequent re-initialization ofdest (via calls tova_start orva_copy).
Contents |
| dest | - | an instance of theva_list type to initialize |
| src | - | the sourceva_list that will be used to initializedest |
(none)
#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);returnsqrt(sum_sq_diff/ count);} int main(void){printf("%f\n", sample_stddev(4,25.0,27.3,26.9,25.7));}
Possible output:
0.920258
| accesses the next variadic function argument (function macro)[edit] | |
| ends traversal of the variadic function arguments (function macro)[edit] | |
| holds the information needed byva_start,va_arg,va_end, andva_copy (typedef)[edit] | |
| enables access to variadic function arguments (function macro)[edit] | |
C++ documentation forva_copy | |
