let Composition := requireModule "Composition" in 
let Logic := requireModule "Logic" in 
let Arithmetic := requireModule "Arithmetic" in 
let Error := requireModule "Error" in 
import [nil? cons? head tail (:)] from Builtins in 
import [($) compose flip rec rem] from Composition in 
import [(if) (else) (elif) (||) (&&) (#t) (#f) not] from Logic in 
import [(<=) (>=) (=) (/=) (+) (-) (*) (/) div0 max ceiling] from Arithmetic in 
let emptySet := in 
let adjoin := \e \A in 
let unite := \A \B in 
let intersect := \A \B in 
let (∩) := intersect in 
let (∪) := unite in 
let contains? := \e \A in 
let (∈) := contains? in 
let subset? := \A \B in 
let superset? := \A \B subset? B A in 
let properSubset? := \A \B (subset? A B) && (not (subset? B A)) in 
let properSuperset? := \A \B properSubset? B A in 
let (=) := \A \B subset? A B && subset? B A in 
let (≟) := (=) in 
let (⊂) := properSubset? in 
let (⊃) := properSuperset? in 
let (⊆) := subset? in 
let (⊇) := superset? in 
let (-) := \A \B in 
let listOf := \A in 
Composition.dispatch1 (#exports[emptySet adjoin unite intersect (∩) (∪) contains? (∈) subset? superset? properSubset? properSuperset? (=) (≟) (⊂) (⊃) (⊆) (⊇) (-) listOf])