(examples-for all?

("true when all items are numeric"
 (all? num? '(1 2 3 4))
 t)

("false when all items are not numeric"
 (all? num? '(1 2 x 4))
 nil)

("true for an atom"
 (and (all? string? "really, all") t)
 t)

("false for nil"
 (all? x1 nil)
 nil)

("false when any item is nil"
 (and (all? x1 '(1 2 nil 4)) t)
 nil))