C ++类模板是一个模板：模板参数无效 [英] C++ class template is a template: template argument is invalid

问题描述

我有一个类模板的问题。我希望类中的私有数据是某种数字类型的向量的向量，即：

I have a problem with a class template. I want the private data in a class to be a vector of vectors of some kind of numeric type, i.e:

std::vector<std::vector<double> >
std::vector<std::vector<std::complex<double> > >

但我想要的矢量类型（我使用的第三方矢量库和stl向量）和要模板化的元素类型。我试过模板模板，但现在我不认为这是我的问题的解决方案。一个高度简化的例子是：

But I want the type of vector (I'm using a library of third party vectors along with stl vectors), and the element type to be templated. I tried template templates but now I don't think that is the solution to my problem. A highly simplified example is:

#include <complex>
#include <vector>
template<typename T>
class Fred {
    std::vector<T> data_;
};
int main(){
    Fred<std::vector<double> > works;
    //Fred<std::vector<std::complex<double> > doesnt_work;
    return 0;
}

如图所示，它编译正常，但如果我取消注释main中的第二行，我收到错误（g ++ 4.6）：

As shown it compiles fine, but if I uncomment the second line in main, I get the error (g++ 4.6):

error: template argument 1 is invalid

为什么会收到这个错误？任何人都有建议的修复？
谢谢！

Why do I get this error? And does anyone have a suggested fix? Thanks!

推荐答案

#include <complex>
#include <vector>
template<typename T>
class Fred {
    std::vector<T> data_;
};

int main(){
    //Fred<std::vector<double> > works;
    Fred<std::vector<std::complex<double> > > doesnt_work;
    return 0;
}

您错过了 doesnt_work 声明中的第三个> 。

Works well. You miss third > in declaration of doesnt_work.

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