The call ratio(C, x) returns a list of ratios which can be used to determine which equation in C is most restrictive with respect to the next simplex pivot.  For each equation, the ratio computed, if possible, is

All negative ratios are reported as infinity, as are those for which the denominator is 0.

The equations C are in the special form produced by simplex[setup].

The command with(simplex,ratio) allows the use of the abbreviated form of this command.