- -1: A singular matrix has been found during the scheme (not applicable if we use Newton with a constant )
- 0: Newton has not converged after
`MaxIter`iteration - 1: Newton has converged toward solution
`Input` - 2: only valid for the implementation in which the function
evaluation return an interval vector. It has not been possible to find
a solution such that all the mid point of the interval evaluation of
the function was at a distance less than
`Accuracy`from 0. However the procedure will return as solution the point obtained during Newton iteration for which the interval evaluation of all the function include 0 and has the minimal average value for the width of the interval evaluation of the functions.

Jean-Pierre Merlet 2012-12-20