X-Git-Url: http://lambda.jimpryor.net/git/gitweb.cgi?p=lambda.git;a=blobdiff_plain;f=arithmetic.mdwn;h=bc531ecddac814bf05bd763e06c24a01b7f04d24;hp=bc15ae8de777a3ad40fe126cbe7500f02edd4890;hb=0b12f248cc9c6b7361a5e3b72d3096a264eec82f;hpb=cbb48495bd8cd6cdcbebd1bcd8c3051148c8b0a6

diff --git a/arithmetic.mdwn b/arithmetic.mdwn
index bc15ae8d..bc531ecd 100644
--- a/arithmetic.mdwn
+++ b/arithmetic.mdwn
@@ -44,8 +44,20 @@ Here are a bunch of pre-tested operations for the untyped lambda calculus. In so
 	let map = \f lst. lst (\h sofar. make_list (f h) sofar) empty  in
 	let filter = \f lst. lst (\h sofar. f h (make_list h sofar) sofar) empty  in ; or
 	let filter = \f lst. lst (\h. f h (make_list h) I) empty  in
-	let reverse = \lst. lst (\h t. t make_list (\f n. f h n)) empty  in
-	
+
+	; append list2 to list1 with: list1 make_list list2
+	let singleton = \x f z. f x z  in
+	let reverse = \lst. lst (\h sofar. sofar make_list (singleton h)) empty  in
+	let zip = \left right. left (\h sofar. sofar (\x y. isempty y
+										sofar
+										(make_pair (make_list (\u v. head y (u v) h) x) (tail y))
+									)
+									(make_pair empty (map right (\h u v. u v h)))
+								)
+						(\x y. reverse x)  in
+	let all = \f lst. lst (\h sofar. and sofar (f h)) true  in
+	let any = \f lst. lst (\h sofar. or sofar (f h)) false  in
+
 
 	; version 1 lists