let true = \x y. x in
let false = \x y. y in
let and = \l r. l (r true false) false in
-let make_pair = \f s g. g f s in
+let make\_pair = \f s g. g f s in
let fst = true in
let snd = false in
-let empty = make_pair true junk in
+let empty = make\_pair true junk in
let isempty = \x. x fst in
-let make_list = \h t. make_pair false (make_pair h t) in
+let make\_list = \h t. make\_pair false (make\_pair h t) in
let head = \l. isempty l err (l snd fst) in
let tail = \l. isempty l err (l snd snd) in
-
+;
; a list of numbers to experiment on
-let mylist = make_list 1 (make_list 2 (make_list 3 empty)) in
-
+let mylist = make\_list 1 (make\_list 2 (make\_list 3 empty)) in
+;
; church numerals
let iszero = \n. n (\x. false) true in
let succ = \n s z. s (n s z) in
let mul = \m n s. m (n s) in
-let pred = \n. iszero n 0 (length (tail (n (\p. make_list junk p) empty))) in
+let pred = \n. iszero n 0 (length (tail (n (\p. make\_list junk p) empty))) in
let leq = \m n. iszero(n pred m) in
let eq = \m n. and (leq m n)(leq n m) in
-
+;
; a fixed-point combinator for defining recursive functions
let Y = \f. (\h. f (h h)) (\h. f (h h)) in
-
+;
let length = Y (\length l. isempty l 0 (succ (length (tail l)))) in
-
+;
; synonyms
-let makePair = make_pair in
+let makePair = make\_pair in
let nil = empty in
let isNil = isempty in
-let makeList = make_list in
+let makeList = make\_list in
let isZero = iszero in
let mult = mul in
-
+;
length (tail mylist)
</textarea>