CString.PredSourceThe type of sets.
add x s returns a set containing all elements of s, plus x. If x was already in s, then s is returned unchanged.
remove x s returns a set containing all elements of s, except x. If x was not in s, then s is returned unchanged.
equal s1 s2 tests whether the sets s1 and s2 are equal, that is, contain equal elements.
Gives a finite representation of the predicate: if the boolean is false, then the predicate is given in extension. if it is true, then the complement is given