Successive raising
Using the
raise
operation of exercise
2.83
, modify the
apply-generic
procedure so that it coerces its arguments to have the same type by the method of successive raising, as discussed in this section. You will need to devise a way to test which of two types is higher in the tower. Do this in a manner that is ''compatible'' with the rest of the system and will not lead to problems in adding new levels to the tower.