week3 evaluator fix

[lambda.git] / lambda_library.mdwn

diff --git a/lambda_library.mdwn b/lambda_library.mdwn
index 289b284..ff36375 100644 (file)
--- a/lambda_library.mdwn
+++ b/lambda_library.mdwn
@@ -65,7 +65,7 @@ and all sorts of other places. Others of them are our own handiwork.
        ; 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))
        let reverse = (\make_left_list lst. lst make_left_list empty) (\h t f z. t f (f h z))  in
-       ; zip [a;b;c] [x; y; z] ~~> [(a,x);(b,y);(c,z)]
+       ; 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
                        (make_pair empty (map (\h u. u h) right))
@@ -296,3 +296,28 @@ and all sorts of other places. Others of them are our own handiwork.
 
 
 -->
+
+<!--
+let list_equal =
+    \left right. left
+                ; here's our f
+                (\hd sofar.
+                    ; deconstruct our sofar-pair
+                    sofar (\might_be_equal right_tail.
+                        ; our new sofar
+                        make_pair
+                        (and (and might_be_equal (not (isempty right_tail))) (eq? hd (head right_tail)))
+                        (tail right_tail)
+                    ))
+                ; here's our z
+                ; we pass along the fold a pair
+                ; (might_for_all_i_know_still_be_equal?, tail_of_reversed_right)
+                ; when left is empty, the lists are equal if right is empty
+                (make_pair
+                    (not (isempty right))
+                    (reverse right)
+                )
+                ; when fold is finished, check sofar-pair
+                (\might_be_equal right_tail. and might_be_equal (isempty right_tail))
+-->
+