changes

[lambda.git] / manipulating_trees_with_monads.mdwn

diff --git a/manipulating_trees_with_monads.mdwn b/manipulating_trees_with_monads.mdwn
index e309faa..0d9e33d 100644 (file)
--- a/manipulating_trees_with_monads.mdwn
+++ b/manipulating_trees_with_monads.mdwn
@@ -293,7 +293,7 @@ it through:
 Later, we will talk more about controlling the order in which nodes are visited.
 
 One more revealing example before getting down to business: replacing
 Later, we will talk more about controlling the order in which nodes are visited.
 
 One more revealing example before getting down to business: replacing

-`state` everywhere in `tree_monadize` with `list` gives us
+`state` everywhere in `tree_monadize` with `list` lets us do:

 
        # let decider i = if i = 2 then [20; 21] else [i];;
        # tree_monadize decider t1;;
 
        # let decider i = if i = 2 then [20; 21] else [i];;
        # tree_monadize decider t1;;


@@ -311,11 +311,11 @@ one for each choice of `int`s for its leaves.
 Now for the main point.  What if we wanted to convert a tree to a list
 of leaves?
 
 Now for the main point.  What if we wanted to convert a tree to a list
 of leaves?
 

-       type ('a, 'r) continuation = ('a -> 'r) -> 'r;;
+       type ('r,'a) continuation = ('a -> 'r) -> 'r;;

        let continuation_unit a = fun k -> k a;;
        let continuation_bind u f = fun k -> u (fun a -> f a k);;
        
        let continuation_unit a = fun k -> k a;;
        let continuation_bind u f = fun k -> u (fun a -> f a k);;
        

-       let rec tree_monadize (f : 'a -> ('b, 'r) continuation) (t : 'a tree) : ('b tree, 'r) continuation =
+       let rec tree_monadize (f : 'a -> ('r,'b) continuation) (t : 'a tree) : ('r,'b tree) continuation =

            match t with
            | Leaf a -> continuation_bind (f a) (fun b -> continuation_unit (Leaf b))
            | Node (l, r) -> continuation_bind (tree_monadize f l) (fun l' ->
            match t with
            | Leaf a -> continuation_bind (f a) (fun b -> continuation_unit (Leaf b))
            | Node (l, r) -> continuation_bind (tree_monadize f l) (fun l' ->


@@ -368,7 +368,7 @@ interesting functions for the first argument of `tree_monadize`:
 It's not immediately obvious to us how to simulate the List monadization of the tree using this technique.
 
 We could simulate the tree annotating example by setting the relevant 
 It's not immediately obvious to us how to simulate the List monadization of the tree using this technique.
 
 We could simulate the tree annotating example by setting the relevant 

-type to `('a, 'state -> 'result) continuation`.
+type to `(store -> 'result, 'a) continuation`.

 
 Andre Filinsky has proposed that the continuation monad is
 able to simulate any other monad (Google for "mother of all monads").
 
 Andre Filinsky has proposed that the continuation monad is
 able to simulate any other monad (Google for "mother of all monads").