//! The QR decomposition decomposes a matrix $A$ into the product
//! $$AP^T = QR,$$
//! where $P$ is a permutation matrix, $Q$ is a unitary matrix (represented as a block Householder
//! sequence), and $R$ is an upper trapezoidal matrix.
/// Computing the decomposition.
/// Reconstructing the inverse of the original matrix from the decomposition.
/// Reconstructing the original matrix from the decomposition.
/// Solving a linear system using the decomposition.