[英]Having trouble with C++ variadic template parameters
I'm trying to write a generic function for logging some stuff for debugging, and I want to call it for example like so: 我正在尝试编写一个用于记录一些调试信息的通用函数,我想像这样调用它:
Log("auo", 34); //writes: auo34
Point point;
point.X = 10;
point.Y = 15;
Log(35, point, 10); //writes: 35{10, 15}10
However, I'm having all kinds of problems with parameter packing and unpacking, I can't seem to get the hang of it. 但是,我在参数打包和解包方面遇到了各种各样的问题,我似乎无法掌握它。 Below is the full code:
下面是完整的代码:
struct Point {
long X, Y;
}
std::ofstream debugStream;
template<typename ...Rest>
void Log(Point first, Rest... params) { //specialised for Point
if (!debugStream.is_open())
debugStream.open("bla.log", ios::out | ios::app);
debugStream << "{" << first.X << ", " << first.Y << "}";
Log(params...);
}
template<typename First, typename ...Rest>
void Log(First first, Rest... params) { //generic
if (!debugStream.is_open())
debugStream.open("bla.log", ios::out | ios::app);
debugStream << first;
Log(params...);
}
How do I fix the functions please? 我该如何修复功能?
Take the following simplified version: 请使用以下简化版本:
void print() {}
template<typename First, typename... Rest>
void print(const First& first, const Rest&... rest)
{
std::cout << first;
print(rest...);
}
When sizeof...(Rest) == 0
a call to print()
with no parameters will be issued which requires the base case overload above. 当
sizeof...(Rest) == 0
将调用没有参数的print()
,这需要上面的基本情况重载。
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