ps3 done

1 files changed, 70 insertions, 12 deletions

diff --git a/ps03_evalapply/bnewbold_ps3.txt b/ps03_evalapply/bnewbold_ps3.txt
index 3d80a95..9bcaa26 100644
--- a/ps03_evalapply/bnewbold_ps3.txt
+++ b/ps03_evalapply/bnewbold_ps3.txt
@@ -1,38 +1,96 @@
-;;; 6.945 Problem Set #3
+;;; 6.945 Problem Set #3 Comments
 ;;; 02/25/2009
 ;;; Bryan Newbold <bnewbold@mit.edu>
 
+Note: I loaded the attached file bnewbold_work.scm load.scm and
+load-general.scm after everything else, if that helps you run things!
 
 Problem 3.1
 ------------------------
-(shouldn't be too hard, handling vectors of procedures as procedures)
+Ugh! This was super tricky because compound-procedure? and vector? are not 
+mutually exclusive... this took hours to figure out, the solution of writing
+my own predicate was easy once I knew what the problem was. Of course rereading
+the hints that were emailed out I can see where I went wrong. Stupid! I should
+have just asked!
 
+[see bnewbold_work.scm]
 
 Problem 3.2
 ------------------------
-(use tagged variable symbols?)
-(use tagged function symbols?)
+It would probably make more sense to have some symbols and functions as tagged
+lists with 'self-evaluating-symbol and 'self-evaluating-function or some such,
+but I just went with it.
+
+I only did binary operations because I got the comment "Don't worry about 
+arity!" on my last problem set ;)
+
+For the literal-functions I went a bit over board and only allowed single
+character names and required registration with declare-literal-function.
+
+[see bnewbold_work.scm]
 
 Problem 3.3
 ------------------------
-a.
-(description)
+a. 
+KONS is good enough on it's own because it creates an actual list that can be
+understood by CAR and CDR. The final un-delaying and memoization logic in
+eval and apply are what are doing the heavy lifting. CAR and CDR just choose
+which path evaluation should continue down.
 
-b.
-(description...?)
+b.  
+We have to delay the integrand call even further than kons does; fortunately
+we have good syntax for this now!
+
+#|
+(define (integral (integrand lazy) initial-value dt)
+    (define int
+    (kons initial-value
+            (add-streams (scale-stream integrand dt)
+                        int)))
+    int)
+; integral
+(define (solve f y0 dt)
+    (define y (integral dy y0 dt))
+    (define dy (map-stream f y))
+    y)
+; solve
+(ref-stream (solve (lambda (x) x) 1 0.001) 1000)
+; 2.716923932235896
 
 
 Problem 3.4
 ------------------------
 a.
-(non-memoizing: generation of random lists? generators? streams?)
+I will answer with a quick program (see code).
 
 b.
-(not sure)
+CONS wants a list as it's second argument (at least most schemes, MIT/GNU seems
+a little looser?), (dy lazy memo) would have to get checked sooner rather than
+later.
 
 c.
-(not sure)
+KONS creates some real headache lexical scoping issues which could be hard to
+debug. It's prevalent use could also effectively tie up every potential object
+created, blocking garbage collection.
+
 
 Problem 3.5
 ------------------------
-(ahhh! open ended project!)
+I implemented crude profiling: after evaluating an expression, a table can be
+printed out showing the number of procedure and primative calls. 
+
+A pair of eq-based hash tables are used to store the running call counts.  
+Performance does seem to be negatively effected (eg (fib 12) took 10+ seconds
+using a very crude algorithm vs. almost instant in the top level repl), but
+that might just be the generic dispatch stuff.
+
+I put in code for an enable/disable flag but i'm not sure it's even neccessary.
+
+The most-needed-change is to print just the primative/compound procedure name
+symbols, not their string representations. I wanted to make sure that the
+same procedure by different names would be counted together, but in the end
+it looks like a big mess. My scmutils-enabled version of MIT Scheme has a
+procedure-name method that does the trick, but it doesn't seem to be in the
+default distribution so I left it out.
+
+