如何让我的va_list参数重复自己? [英] How can I get my va_list arguments to repeat itself?
问题描述
这是我第一次使用 va_list
和东西,所以我真的不知道我在做什么。好吧基本上我有一个数字(1,2,3,4,5)在函数排序,我让他们打印出来。这很好。
This is my first time working with va_list
and stuff so I don't really know what I'm doing. Okay basically what I have is a bunch of numbers (1, 2, 3, 4, 5) in the function ordered and I get them to print out. This works fine.
#include <iostream>
#include <cstdarg>
using namespace std;
void ordered(int num1, double list ...);
void main()
{
ordered(5, 1.0, 2.0, 3.0, 4.0, 5.0);
}
void ordered(int num1, double list ...)
{
va_list arguments;
va_start(arguments, num1);
list = va_arg(arguments, double);
cout << "There are " << num1 << " numbers" << endl;
do {
cout << list << endl; // prints out 1 then 2 then 3 then 4 then 5
list = va_arg(arguments, double);
} while (list != 0);
// at this point, list = 0
va_end(arguments);
}
问题是,在 va_end ;
或之前,我想让程序第二次打印我的列表;基本上会再次打印出1,2,3,4,5,而不会产生其他功能。我试着复制代码:
the problem is, after the va_end(arguments);
or before it, I would like to get the program to print out my list a second time; basically print out 1, 2, 3, 4, 5 once more, without making another function. I tried to duplicate the code:
va_start(arguments, num1);
do {
cout << list << endl;
list = va_arg(arguments, double);
} while (list != 0);
va_end(arguments);
没有成功。如何让程序再次重复 list
,或者不可能在同一个函数中再次执行呢?
without success. How can the program to repeat list
once more, or is it not possible to do it again in the same function?
推荐答案
这是一个有效的实现:
#include <iostream>
#include <cstdarg>
using namespace std;
void ordered(int num1, ...); // notice changed signature
int main(int,char**)
{
ordered(5, 1.0, 2.0, 3.0, 4.0, 5.0);
return 0;
}
void ordered(int count, ...) // notice changed signature
{
va_list arguments;
va_start(arguments, count);
cout << "There are " << count << " numbers" << endl;
double value = 0.0;
// notice how the loop changed
for(int i = 0; i < count; ++i) {
value = va_arg(arguments, double);
cout << value << endl; // prints out 1 then 2 then 3 then 4 then 5
}
// at this point, list = 0
va_end(arguments);
va_list arg2;
va_start(arg2, count);
cout << "There are " << count << " numbers" << endl;
for(int i = 0; i < count; ++i) {
value = va_arg(arg2, double);
cout << value << endl; // prints out 1 then 2 then 3 then 4 then 5
}
// at this point, list = 0
va_end(arg2);
}
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