X-Git-Url: http://lambda.jimpryor.net/git/gitweb.cgi?p=lambda.git;a=blobdiff_plain;f=assignment10.mdwn;h=8f52ca20370e879efa536b7d720c5a7d21a6c6dd;hp=ad6ebb14e79aebd19f7733a51135b397f540787d;hb=21c2f56ceac1e9445ee7cc8e15786e9521a40b9b;hpb=c42666baade652387ad72d5109eff241c796edfb

diff --git a/assignment10.mdwn b/assignment10.mdwn
index ad6ebb14..8f52ca20 100644
--- a/assignment10.mdwn
+++ b/assignment10.mdwn
@@ -9,6 +9,25 @@
 	>	it with.
 
 
+	As Ken Shan points out, this is an instance of the algorithm
+	for converting name/year citations (like 'v. Montague 1970')
+	to numerals corresponding to their ('v. [24]').  Except that
+	bibliograpic numerals don't start with zero.
+
+	Give some thought to efficiency: there are straightforward
+	solutions that involve traversing the tree once (in order to,
+	say, construct a suitable mapping from leafs to ints), then
+	traversing it again to do the conversion.  Can you find a
+	solution that traverses the tree exactly once, replacing each
+	leaf as soon as you see it?
+
+	Consider a variation in which you must replace each leaf with
+	is number of occurrences in the tree.  Is there any way to do
+	that with a single traversal?
+
+	You can assume that the tree is leaf-labeled (no labels on the
+	internal nodes), and that the leafs are, say, chars.
+
 	Here is [a hint](/hints/assignment_10_hint).
 
 
@@ -93,7 +112,19 @@
 		       (insert-co new before after (cdr lst) (lambda (new-lst lefts rights) ________))))))
 
 
-6.	Go back to the "abSd" problem we presented in [[From List Zippers to Continuations]]. Consider the "tc" solution which uses explicitly passed continuations. Try to reimplement this using reset and shift instead of having an explicit `k` argument. This will likely be challenging but rewarding. The notes on [[CPS and Continuation Operators]], especially the examples at the end, should be helpful. We are of course also glad to help you out.
+6.	Go back to the "abSd" problem we presented in [[From List Zippers to Continuations]]. Consider the "tc" solution which uses
+explicitly passed continuations. Try to reimplement this using reset
+and shift instead of having an explicit `k` argument. This will likely
+be challenging but rewarding. The notes on [[CPS and Continuation Operators]], especially the examples at the end, should be helpful. We
+are of course also glad to help you out.
+
+    Consider adding a special symbol `'#'` (pronounced 'prompt') to the
+    mini-language such that
+
+    `"ab#cdSef"` ~~> `"abcdcdef"`
+
+    That is, the rule for `'S'` is to copy the preceding string, but
+    only up to the closest enclosing `'#'` symbol.
 
 7.	Can you reimplement your solution to [[assignment9]] using reset and shift?