From: jim <jim@web>
Date: Sun, 8 Feb 2015 01:19:32 +0000 (-0500)
Subject: fix link to hint
X-Git-Url: http://lambda.jimpryor.net/git/gitweb.cgi?p=lambda.git;a=commitdiff_plain;h=b23570f3ffe4fc05de3f291d96b20ce474b1e330;hp=7cc39c68d74503b3ea9d143ebe9acf21ff425042;ds=sidebyside

fix link to hint
---

diff --git a/exercises/assignment2.mdwn b/exercises/assignment2.mdwn
index 946df8fe..f0dbfcd4 100644
--- a/exercises/assignment2.mdwn
+++ b/exercises/assignment2.mdwn
@@ -133,30 +133,10 @@ Folds and Lists
 
 25. We mentioned in the Encoding notes that `fold_left (flipped_cons, []) xs` would give us the elements of `xs` but in the reverse order. That is, this is how we can express `reverse` in terms of `fold_left`. How would you express `reverse` in terms of `fold_right`?
 
-    This problem does have an elegant and concise solution, but it may be hard for you to figure it out. We think it will a useful exercise for you to try, anyway. We'll give a [[hint]]. Don't look at the hint until you've gotten really worked up about the problem. Before that, it probably will just be baffling. If your mind has really gotten its talons into the problem, though, the hint might be just what you need to break it open.
+    This problem does have an elegant and concise solution, but it may be hard for you to figure it out. We think it will a useful exercise for you to try, anyway. We'll give a [[hint|assignment2 hint]]. Don't look at the hint until you've gotten really worked up about the problem. Before that, it probably will just be baffling. If your mind has really gotten its talons into the problem, though, the hint might be just what you need to break it open.
 
     Even if you don't get the answer, we think the experience of working on the problem, and then understanding the answer when we reveal it, will be satisfying and worhtwhile. It also fits our pedagogical purposes for one of the recurring themes of the class.
 
-<!--
-Hint. Suppose the list we want to reverse is [10, 20, 30]. Applying `fold_right` to this will begin by computing `f 30 z` for some `f` and `z` that we specify. If we made the result of that be something like `30 & blah`, or any larger structure that contained something of that form, it's not clear how we could, using just the resources of `fold_right`, reach down into that structure and replace the `blah` with some other element, as we'd evidently need to, since after the next step we should get `30 & (20 & blah)`. What we'd like instead is something like this:
-
-    30 & < >
-
-Where `< >` isn't some *value* but rather a *hole*. Then with the next step, we want to plug into that hole `20 & < >`, which contains its own hole. Getting:
-
-    30 & (20 & < >)
-
-And so on. That is the key to the solution. The questions you need to answer, to turn this into something executable, are:
-
-1. What is a hole? How can we implement it?
-
-2. What should `f` be, so that the result of `f (20, 30 & < >)`, is `30 & (20 & < >)`?
-
-3. What should `z` be, so that the result of `f (30, z)` is `30 & < >`?
-
-4. At the end of the `fold_right`, we're going to end with something like `30 & (20 & (10 & < >))`. But what we want is `[30, 20, 10]`. How can we turn what we've gotten into what we want?
-
--->
 
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