Question

Let’s say I have two Matrice classes. One matrix is 2 by 2, the other 3 by 3 and then I go to multiply them together. Of course I cannot multiply two matrices that don’t have the same dimensions.

I am aware that I can build in a run-time check, but is there a way to build in a compile-time check using the c++ language? So if I try to compile a program where two defined matrices of different dimensions are multiplied it will through a compile-time error.

Matrix *matrix1 = new Matrix(2,2);
Matrix *matrix2 = new Matrix(3,3);

Matrix_Multiply(matrix1,matrix2);  // compiler throws error on this line 

Also while we are on this topic, are there any programming languages that have this feature?

Answer 1

The answer depends on how your matrices get a dimension: If the dimensions are determined at run-time, there is no compile-time check. However, if the matrices are compile-time dimensioned, I’d think that you’ll naturally end up having compile time checks:

template <typename T, int Width, int Height>
class Matrix;

template <typename T, int M, int N, int O>
Matrix<T, M, O> operator* (Matrix<T, M, N> const& lhs, Matrix<T, N, O> const& rhs);

That is, the size of the result matrix is deduced by the sizes of the two argument matrices. If they have mismatching dimensions, no suitable multiplication operator would be found.