C++ 模板类型定义

C++ template typedef(C++ 模板类型定义)

问题描述

我有课

template<size_t N, size_t M>
class Matrix {
    // ....
};

我想创建一个 typedef，它创建一个 Vector(列向量)，它等效于大小为 N 和 1 的 Matrix.类似的东西:

I want to make a typedef which creates a Vector (column vector) which is equivalent to a Matrix with sizes N and 1. Something like that:

typedef Matrix<N,1> Vector<N>;

这会产生编译错误.以下创建了类似的东西，但不完全是我想要的:

Which produces compile error. The following creates something similar, but not exactly what I want:

template <size_t N>
class Vector: public Matrix<N,1>
{ };

是否有解决方案或不太昂贵的解决方法/最佳实践?

Is there a solution or a not too expensive workaround / best-practice for it?

推荐答案

C++11新增别名声明，是typedef的泛化，允许模板:

C++11 added alias declarations, which are generalization of typedef, allowing templates:

template <size_t N>
using Vector = Matrix<N, 1>;

Vector<3> 类型等价于 Matrix<3, 1>.

在 C++03 中，最接近的近似值是:

In C++03, the closest approximation was:

template <size_t N>
struct Vector
{
    typedef Matrix<N, 1> type;
};

这里，类型 Vector<3>::type 等价于 Matrix<3, 1>.

Here, the type Vector<3>::type is equivalent to Matrix<3, 1>.

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