X-Git-Url: http://lambda.jimpryor.net/git/gitweb.cgi?p=lambda.git;a=blobdiff_plain;f=lambda_library.mdwn;h=579668bed6323e3a976b8a70d599f537a82fbcca;hp=2e65f5ccea0e224fdeb262b6dcc2ad10fd9700c8;hb=8ef02c87c6608f870322ca38033c372b50890ef2;hpb=7369cbe617f9b283dc9a585858dd1085ff7266f8

diff --git a/lambda_library.mdwn b/lambda_library.mdwn
index 2e65f5cc..579668be 100644
--- a/lambda_library.mdwn
+++ b/lambda_library.mdwn
@@ -63,8 +63,12 @@ and all sorts of other places. Others of them are our own handiwork.
 	; very inefficient but correct reverse
 	let reverse = \lst. lst (\h sofar. append sofar (singleton h)) empty  in ; or
 	; more efficient reverse builds a left-fold instead
-	; (make_left_list a (make_left_list b (make_left_list c empty)) ~~> \f z. f c (f b (f a z))
+	; make_left_list a (make_left_list b (make_left_list c empty)) ~~> \f z. f c (f b (f a z))
 	let reverse = (\make_left_list lst. lst make_left_list empty) (\h t f z. t f (f h z))  in
+	; most elegant
+	; revappend [a;b;c] [x;y] ~~> [c;b;a;x;y]
+	let revappend = \lst. lst (\hd sofar. \lst. sofar (make_list hd lst)) I  in
+	let rev = \lst. revappend lst empty  in
 	; zip [a;b;c] [x;y;z] ~~> [(a,x);(b,y);(c,z)]
 	let zip = \left right. (\base build. reverse left build base (\x y. reverse x))
                        ; where base is