Incomplete definition

Excuse me if I'm being too strict here but there seems to be a glaring gap in the definition of what a PRC(squared) class is on p42 of the textbook.

The definition states that
1) the initial functions must belong to the class,
2) a function obtained from functions belonging to the class (by either composition or recursion) also belongs to the class

From experience in previous modules, it seems that the definition is missing a 3rd point:

3) Only the functions which qualify through 1) and 2) belong the the class.

Without point 3), any other function I choose could also be included in the class, since points 1) and 2) have already been fulfilled.

assignment 2 right? sorry, have not got that far yet. I stil lwant to know if the due date for the assignment is 15 june or 15 july....

I would agree on 3, but the way the definition is constructed implies that not all functions have been identified in PRC and hence by point number 2, any new functions not known to be part of PRC but derived from PRC are part of PRC. The definition seems to be based on an inductive principle, not a classifying one (which would make your point valid).

BTW, hope by now you've realized it is not PRC(squared) just PRC. The 2 is a footnote.