The non-zero arity actions (non-terminals) for both main population and SMART operator programs are: ADD, SUB, MULT, DIV, READ, WRITE, ADF, IF-THEN-ELSE, PIFTE, MAX, MIN, LESS-THAN, EQUAL, NOT.
MAX and MIN double as OR and AND. All non-zero numbers are treated as TRUE and 0 as FALSE. PIFTE is a probabilistic IF-THEN-ELSE that takes 3 arguments. A random number is chosen and if it is less than arg1 then arg2 is returned, else arg3 is returned. ``Returned'' in the PADO context is equivalent to ``pushed onto the argument stack.'' ``Takes X arguments'' in the PADO context means ``pops X elements off the argument stack to use as input.'' In this chapter, the main population programs were given access to Library programs through a LIBRARY[i] action. In addition, there are six signal-access actions that the PADO programs discussed in this chapter were given. These functions are {POINT, AVERAGE, MOST, LEAST, VARIANCE, DIFFERENCE}. More detail on them can be seen in [Teller and Veloso 1995a, 1995b].
Table 3.1: Branch-decision function templates
The branch-decision function at a specific node is one of a preset set
of function templates (table 3.1). 
and
(table 3.1) can be any two of these three
things: the action type of the temporally previous node (e.g.
``WRITE''), the result of the action of the current node, and the
node's branch-decision constant. The branch-decision function
compares these two values through one of the twelve choices in
table 3.1, and (for this chapter) follows 
on
FALSE and 
on TRUE.