1  ($define null "the empty bunch")
 2  ($define pred "all predicates")
 3  ($define elem "all elements (non bunches)")
 4  ($define p (var pred))
 5  ($define e (var elem))
 6  ($define t1 (var anything))
 7  ($define t2 (var anything))
 8  
 9  ($define '(∀ null p) #T)
10  ($define '(= (∀ e p) (p e)) #T)
11  ($define '(= (∀ (∪ t1 t2) p)
12               (∧ (∀ t1 p)
13                  (∀ t2 p)))
14    #T)
15  
16  
17  
18  ($define b (var boolean))
19  ($define '(is? pred ($lambda (x) b)) #T)