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#2
rjsp2022-10-14 14:35
 程序代码：#include <stdio.h> #include <stdarg.h> double average( size_t num, ... ) { va_list valist; va_start( valist, num ); double sum = 0; for( size_t i=0; i!=num; ++i ) { int val = va_arg(valist, int); printf( "item(%zu) = %d\n", i, val ); sum += val; } va_end(valist); return num==0 ? 0 : sum/num; } int main( void ) { printf( "Average of { 2, 3, 4, 5 } = %f\n", average(4, 2,3,4,5) ); } 输出 item(0) = 2 item(1) = 3 item(2) = 4 item(3) = 5 Average of { 2, 3, 4, 5 } = 3.500000 |
程序代码：#include <stdio.h>
#include <stdarg.h>
double average(int num,...)
{
va_list valist;
int sum = 0.0;
int i;
/* 为 num 个参数初始化 valist */
va_start(valist, num);
/* 访问所有赋给 valist 的参数 */
for (i = 0; i < num; i++)
{
sum = va_arg(valist, int);
printf("sum = %d\n", sum);
}
/* 清理为 valist 保留的内存 */
va_end(valist);
return sum/num;
}
int main()
{
printf("Average of 2, 3, 4, 5 = %d\n", average(4, 2,3,4,5));
}
问题：
1、va_list valist; 其中的 valist; 是变量吧？
2、printf("Average of 2, 3, 4, 5 = %d\n", average(4, 2,3,4,5)); 打印后，它的值怎么会是 “Average of 2, 3, 4, 5 = 4202508” ？ 这个4202508怎么出来的？