stdvectorstdvectordouble LinAlgsubtractionstdvectorstdvectordouble A stdvectorstdvectordouble B stdvectorstdvectordouble C; CresizeAsize; forint i = 0; i Csize; i++ Ci

The code above defines three functions in the LinAlg namespace for matrix operations: subtraction, matrix multiplication, and Hadamard product.

The subtraction function takes two matrices A and B of the same size and returns their element-wise difference as a new matrix C.

The matrix multiplication function takes two matrices A and B and returns their product as a new matrix C. This operation is defined for matrices where the number of columns in A equals the number of rows in B.

The Hadamard product function takes two matrices A and B of the same size and returns their element-wise product as a new matrix C.

All three functions create a new matrix C to store the result of the operation, with the size of C determined by the size of the input matrices A and B.

The code uses nested for loops to perform the element-wise operations on each element of the matrices. The Hadamard product and subtraction functions use a straightforward approach, while the matrix multiplication function uses a triple nested loop to calculate the dot product of each row of A with each column of B