Determinant in Haskell

In linear algebra, the determinant is quite a useful operation that can be done on matrices. To further my understanding of Haskell, I decided to program a solver for systems of equations. One of the best ways to do this dynamically is through Cramer's Rule which needs to be able to calculate determinants. So, here's my recursive code for finding determinants:

determinant :: (Num a, Fractional a) => [[a]] -> a

determinant [[x]] = x
determinant mat =
 sum [(-1)^i*x*(determinant (getRest i mat)) | (i, x) <- zip [0..] (head mat)]

So, in this code, the base case is a 1x1 matrix. The getRest function simply returns the matrix without the head row (topmost) and without the \(i\)th column.

The code and tests are available on my github.