let true = \x y. x in
let false = \x y. y in
let and = \l r. l (r true false) false in
+let or = \l r. l true r in
+;
let make\_pair = \f s g. g f s in
let get\_fst = true in
let get\_snd = false in
let isZero = iszero in
let mult = mul in
;
+let t1 = (make\_list 1 empty) in
+let t2 = (make\_list 2 empty) in
+let t3 = (make\_list 3 empty) in
+let t12 = (make\_list t1 (make\_list t2 empty)) in
+let t23 = (make\_list t2 (make\_list t3 empty)) in
+let ta = (make\_list t1 t23) in
+let tb = (make\_list t12 t3) in
+let tc = (make\_list t1 (make\_list t23 empty)) in
+;
+;sum-leaves t1 ; ~~> 1
+;sum-leaves t2 ; ~~> 2
+;sum-leaves t3 ; ~~> 3
+;sum-leaves t12 ; ~~> 3
+;sum-leaves t23 ; ~~> 5
+;sum-leaves ta ; ~~> 6
+;sum-leaves tb ; ~~> 6
+;
length (tail mylist)
</textarea>