从返回类型推断类型T的模板 [英] Templates inferring type T from return type

问题描述

我有一个如下模板:

template <class T>
vector<T> read_vector(int day)
{
  vector<T> the_vector;
  {...}
  return the_vector;
}

我希望能够做类似的事情

I would like to be able to do something like

vector<int> ints = read_vector(3);
vector<double> doubles = read_vector(4);

C ++模板是否可以从调用它们的时间推断出返回类型，还是我应该将虚拟参数传递给具有想要矢量具有的类型的模板?后者有效，但更麻烦.

Is it possible for C++ templates to infer the return type from when they're called, or should I just pass a dummy argument to the template with the type I want to the vector to have? The latter works but is messier.

推荐答案

#include <vector>

struct read_vector
{
    int day;
    explicit read_vector(int day) : day(day) {}

    template <typename T, typename A>  
    operator std::vector<T, A>()
    {
        std::vector<T, A> v;
        //...
        return v;
    }
};

int main()
{
    std::vector<int> ints = read_vector(3);
    std::vector<double> doubles = read_vector(4);
}

演示

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