Most of the procedures in ALIAS will accept as optional last argument the name of a simplification procedure: a user-supplied procedure that take as input the current box and proceed to some further reduction of the width of the box or even determine that there is no solution for these box, in which case it should return -1. Such procedure must be implemented as:
int Simp_Proc(INTERVAL_VECTOR & P)where P is the current box. This procedure must return either -1 or any other integer. If a reduction of an interval is done within this procedure, then P must be updated accordingly.
This type of procedure allows the user to add information to the algorithm without having to add additional equations. The simplification procedure is applied on a box before the bisection and is used within the 3B method if this heuristic is applied.
Note that the Maple package associated to ALIAS allows in some cases to produce automatically the code for such procedure (see the ALIAS-Maple manual) and that section 2.17 presents a standard simplification procedure that may be used for almost any system of equations.