| * Add an inline version of the iterate method for speed? Perhaps not, | |
| the time taken for each iteration surely dominated by the convergence | |
| test. | |
| * Numerical derivatives? Maybe have a function to manufacture an fdf | |
| from an f and optionally a df. (We'll need to approximate the | |
| derivative if it is not provided; this is something which should be | |
| done outside the root finding package.) | |