From: Jim Pryor <profjim@jimpryor.net>
Date: Mon, 13 Dec 2010 06:28:25 +0000 (-0500)
Subject: transformers tweak
X-Git-Url: http://lambda.jimpryor.net/git/gitweb.cgi?p=lambda.git;a=commitdiff_plain;h=e948c27044f69962483a6c62a8568b84acd5be85;ds=sidebyside

transformers tweak

Signed-off-by: Jim Pryor <profjim@jimpryor.net>
---

diff --git a/monad_transformers.mdwn b/monad_transformers.mdwn
index b40661a8..086a2ffc 100644
--- a/monad_transformers.mdwn
+++ b/monad_transformers.mdwn
@@ -306,8 +306,8 @@ Our Tree monad has a corresponding TreeT transformer. Simplified, its implementa
 				  reader_unit (Node(ls, rs))))
 		in loop us);;
 
-	let tree_reader_elevate (w : 'a reader) : 'a tree_reader =
-		reader_bind w (fun a -> reader_unit (Leaf a))
+	let tree_reader_elevate (inner : 'a reader) : 'a tree_reader =
+		reader_bind inner (fun a -> reader_unit (Leaf a))
 
 Recall our earlier definition of `tree_monadize`, specialized for the Reader monad:
 
@@ -317,9 +317,9 @@ Recall our earlier definition of `tree_monadize`, specialized for the Reader mon
 			(* the next line is equivalent to: tree_reader_elevate (f a) *)
 	        reader_bind (f a) (fun b -> reader_unit (Leaf b))
 	    | Node (l, r) ->
-	        reader_bind (tree_monadize f l) (fun l' ->
-	          reader_bind (tree_monadize f r) (fun r' ->
-	            reader_unit (Node (l', r'))));;
+	        reader_bind (tree_monadize f l) (fun ls ->
+	          reader_bind (tree_monadize f r) (fun rs ->
+	            reader_unit (Node (ls, rs))));;
 
 We rendered the result type here as `'b tree reader`, as we did in our earlier discussion, but as we can see from the above implementation of TreeT(Reader), that's the type of an `'b tree_reader`, that is, of a layered box consisting of TreeT packaging wrapped around an inner Reader box.