可变参数的 C++ 重载运算符逗号

2022-01-21 00:00:00 operators arguments variadic c++ comma-operator

是否可以通过重载参数的运算符逗号来构造函数的可变参数?我想看一个例子如何做到这一点..，也许是这样的:

is it possible to construct variadic arguments for function by overloading operator comma of the argument? i want to see an example how to do so.., maybe something like this:

template <typename T> class ArgList {
public:
    ArgList(const T& a);
    ArgList<T>& operator,(const T& a,const T& b);
}
//declaration
void myFunction(ArgList<int> list);

//in use:
myFunction(1,2,3,4);

//or maybe:
myFunction(ArgList<int>(1),2,3,4);

推荐答案

有点可能，但使用起来不太好.例如:

It is sort-of possible, but the usage won't look very nice. For exxample:

#include <vector>
#include <iostream>
#include <algorithm>
#include <iterator>

template <class T>
class list_of
{
    std::vector<T> data;
public:
    typedef typename std::vector<T>::const_iterator const_iterator;
    const_iterator begin() const { return data.begin(); }
    const_iterator end() const { return data.end(); }

    list_of& operator, (const T& t) {
        data.push_back(t);
        return *this;
    }
};

void print(const list_of<int>& args)
{
    std::copy(args.begin(), args.end(), std::ostream_iterator<int>(std::cout, " "));
}

int main()
{
    print( (list_of<int>(), 1, 2, 3, 4, 5) );
}

这个缺点将在 C++0x 中得到修复，你可以这样做:

This shortcoming will be fixed in C++0x where you can do:

void print(const std::initializer_list<int>& args)
{
    std::copy(args.begin(), args.end(), std::ostream_iterator<int>(std::cout, " "));
}

int main()
{
    print( {1, 2, 3, 4, 5} );
}

甚至是混合类型:

template <class T>
void print(const T& t)
{
    std::cout << t;
}

template <class Arg1, class ...ArgN>
void print(const Arg1& a1, const ArgN& ...an)
{
    std::cout << a1 << ' ';
    print(an...);
}


int main()
{
    print( 1, 2.4, 'u', "hello world" );
}

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