From 2466770c4ba4b1cf44894bce96cbf12434d4f4ed Mon Sep 17 00:00:00 2001
From: Jim Pryor <profjim@jimpryor.net>
Date: Tue, 14 Sep 2010 09:09:24 -0400
Subject: [PATCH 1/1] add damn3.rkt

Signed-off-by: Jim Pryor <profjim@jimpryor.net>
---
 damn3.rkt | 67 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 67 insertions(+)
 create mode 100644 damn3.rkt

diff --git a/damn3.rkt b/damn3.rkt
new file mode 100644
index 00000000..a087b4bc
--- /dev/null
+++ b/damn3.rkt
@@ -0,0 +1,67 @@
+#lang racket
+(require racket/control)
+
+(define damn0 (lambda ()
+				'id))
+
+(define damn1 (lambda ()
+				(cons '("side effect" bad)
+					  'id)))
+
+(define damn2 (lambda () (shift k
+								(cons '("side effect" bad) 
+									  (list (k 'id))))))
+
+(define damn3 (lambda () (shift k
+								(list (k 'id)
+									  '("side effect" bad)))))
+
+
+; Now if we use damn0, our compositional semantics will work OK but
+; we don't yet have any expressive contribution:
+
+(list "main content" 'i (list 'like (list 'the (damn0) 'boy)))
+; '("main content" i (like (the id boy)))
+
+
+; If we use damn1, we've added in the expressive side-effect:
+
+(list "main content" 'i (list 'like (list 'the (damn1) 'boy)))
+; '("main content" i (like (the (("side effect" bad) . id) boy)))
+
+; However, the context (list 'the ... 'boy) is now being asked to operate
+; on an element (("side effect" bad) . id), and it may complain it doesn't
+; know what that is. It knows how to use 'id to get (list 'the 'id 'boy),
+; and how to use 'bad to get (list 'the 'bad 'boy), but we're supposed to
+; have something different here.
+
+; To get what we want we need to use (delimited) continuations:
+(reset (list "main content" 'i (list 'like (list 'the (damn2) 'boy))))
+; '(("side effect" bad) ("main content" i (like (the id boy))))
+
+; or to get the side effect at the end:
+
+(reset (list "main content" 'i (list 'like (list 'the (damn3) 'boy))))
+; '(("main content" i (like (the id boy))) ("side effect" bad))
+
+; If you're working in the interactive interpreter, the outermost "reset" here
+; is already in its default position, so it doesn't need to be explicitly
+; specified:
+
+(list "main content" 'i (list 'like (list 'the (damn2) 'boy)))
+; '(("side effect" bad) ("main content" i (like (the id boy))))
+
+; However, if you're executing this as a file, you would need to include explicit resets.
+
+
+
+; Instead of using reset/shift you could use an element like "print" in
+; building the side-effect, as we did in class. Here you wouldn't require an
+; explicit continuation, but as Chris said, that's because "print" already
+; represents an implicit continuation.
+
+(define damn4 (lambda () (begin (print "bad") 'id)))
+(list "main content" 'i (list 'like (list 'the (damn4) 'boy)))
+; "bad"'("main content" i (like (the id boy)))
+;
+
-- 
2.11.0