Merge branch 'master' of ssh://server.philosophy.fas.nyu.edu/Users/lambda/lambda

[lambda.git] / week11.mdwn

diff --git a/week11.mdwn b/week11.mdwn
index 1857d8b..0128a5d 100644 (file)
--- a/week11.mdwn
+++ b/week11.mdwn
@@ -1,22 +1,11 @@
 These notes may change in the next few days (today is 30 Nov 2010).
 The material here benefited from many discussions with Ken Shan.
 
 These notes may change in the next few days (today is 30 Nov 2010).
 The material here benefited from many discussions with Ken Shan.
 

-[[!toc]]
+##[[Tree and List Zippers]]##

 
 

-##List Zippers##
+##[[Coroutines and Aborts]]##

 
 

-Say you've got some moderately-complex function for searching through a list, for example:
-
-       let find_nth (test : 'a -> bool) (n : int) (lst : 'a list) : (int * 'a) ->
-               let rec helper (position : int) n lst =
-                       match lst with
-                       | [] -> failwith "not found"
-                       | x :: xs when test x -> (if n = 1
-                               then (position, x)
-                               else helper (position + 1) (n - 1) xs
-                       )
-                       | x :: xs -> helper (position + 1) n xs
-               in helper 0 n lst;;
+##[[From Lists to Continuations]]##

 
 This searches for the `n`th element of a list that satisfies the predicate `test`, and returns a pair containing the position of that element, and the element itself. Good. But now what if you wanted to retrieve a different kind of information, such as the `n`th element matching `test`, together with its preceding and succeeding elements? In a real situation, you'd want to develop some good strategy for reporting when the target element doesn't have a predecessor and successor; but we'll just simplify here and report them as having some default value:
 
 
 This searches for the `n`th element of a list that satisfies the predicate `test`, and returns a pair containing the position of that element, and the element itself. Good. But now what if you wanted to retrieve a different kind of information, such as the `n`th element matching `test`, together with its preceding and succeeding elements? In a real situation, you'd want to develop some good strategy for reporting when the target element doesn't have a predecessor and successor; but we'll just simplify here and report them as having some default value:
 


@@ -1760,4 +1749,7 @@ called a
 that is intended to 
 represent non-deterministic computations as a tree.
 
 that is intended to 
 represent non-deterministic computations as a tree.
 

+##[[List Monad as Continuation Monad]]##
+
+##[[Manipulating Trees with Monads]]##