X-Git-Url: http://lambda.jimpryor.net/git/gitweb.cgi?p=lambda.git;a=blobdiff_plain;f=assignment3.mdwn;h=e240b732b1405e176d696bbab3c5974a1d125f35;hp=8a4efcc0d34dd9de201013699e3156f7de26cc2c;hb=303e7febec777213e5e8d2b305406c2684dcac6a;hpb=29f15e8e027b34b893874598824bdbff45096c78 diff --git a/assignment3.mdwn b/assignment3.mdwn index 8a4efcc0..e240b732 100644 --- a/assignment3.mdwn +++ b/assignment3.mdwn @@ -42,6 +42,7 @@ Recall that version 1 style lists are constructed like this (see ; church numerals let iszero = \n. n (\x. false) true in let succ = \n s z. s (n s z) in + let add = \l r. l succ r in let mul = \m n s. m (n s) in let pred = (\shift n. n shift (make\_pair 0 0) get\_snd) (\p. p (\x y. make\_pair (succ x) x)) in let leq = \m n. iszero(n pred m) in @@ -50,6 +51,7 @@ Recall that version 1 style lists are constructed like this (see ; 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 + let fold = Y (\f l g z. isempty l z (g (head l)(f (tail l) g z))) in eq 2 2 yes no