private Mx leftContract(final Mx original) {
final VecBasedMx contracted = new VecBasedMx(original.rows(), original.columns() - 1);
for (int i = 0; i < contracted.rows(); i++) {
for (int j = 0; j < contracted.columns(); j++) {
contracted.set(i, j, original.get(i, j + 1));
}
}
return contracted;
}
