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Why typedef pattern causes problem in C ++ (not C ++ 11)

In this question, OP requested a typedef template solution that is not possible in C ++. The OP also presented the solution on its own, but he did not like it:

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

// Problem - will not compile
typedef Matrix<N,1> Vector<N>;

// Solution
template <int N>
class Vector: public Matrix<N,1>
{ };

My question is: what advantage does the OP solution Helper::type give us (assuming these classes are never intended to be used by a base pointer or new'd as such)? An empty class should not have overhead in the release (or does it?). The only drawback that I see is that in debug builds you have to extend the base class when debugging.

EDIT: , . @Dani, , , .

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3

typedef . - .

,

template<size_t N, size_t M>
Matrix<N, M> * createMatrix();


Vector<3>::type * var = createMatrix<3, 1>();

.

Vector<3> * var = createMatrix<3, 1>();

.

+7

, ( ++ 11 ). , , , .

+7

In addition to each taste in the syntax (which may be subjective), the main difference is that, by means of a vector, a vector is actually another type that decomposes into a matrix, and when using an assistant containing typedef, the vector is an alias of the matrix (at least for partial specialization).

The difference requires that the vector redefine the constructors (which were not inherited) or some potential traps in the case of operations defined in terms of specialized specialization (with typedef, they will never be considered as "differnet")

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