CODEWITHSUNDEEP
c++classtemplates
m.a.g
m.a.g

Reputation: 21

Combining matrices with different sizes using C++ templates

I have a templated class called Matrix with the following template parameters:

template <typename T, int rows, int columns>
class Matrix
{
...
}

I want to write a function called Augment that augments (just combines the two side by side) two matrices of different sizes into a new matrix. For example: 3x1 + 3x2 = 3x3.

Written in C++, the objects would look like this:

Matrix<int, 3, 1> a;
Matrix<int, 3, 2> b;
Matrix<int, 3, 3> c = a.Augment(b);

I have my class function declaration as follows:

template <int newColumns, int otherColumns>
Matrix<T, rows, newColumns> Augment(const Matrix<T, rows, otherColumns>& other)

However, I am getting an error:

no instance of function template
"Matrix<T, rows, columns::Augment [with T=int, rows=3, columns=1]" matches the argument list
    argument types are: (Matrix<int, 3, 2>)
    object type is: Matrix<int, 3, 1>.

I have tried these template parameters with no luck so far, I still get the same error:

Upvotes: 1

Views: 59

Answers (2)

Erdal K&#252;&#231;&#252;k
Erdal K&#252;&#231;&#252;k

Reputation: 5830

With C++20, you could do something like this:

constexpr auto Augment(const auto& other)
{
    constexpr auto new_cols = 3; //or whatever new columns is
    return Matrix<T, rows, new_cols>{};
}

A full example can be seen here: https://godbolt.org/z/s5xnKWvcc

Upvotes: 0

zdan
zdan

Reputation: 29450

The compiler can't deduce newColumns with the signature you've provided it. How about this:

template <int otherColumns> 
Matrix<T, rows, columns+otherColumns> Augment(const Matrix<T, rows, otherColumns>& other);

Upvotes: 2

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