[Fwd: Re: [plt-scheme] Scheme Program]

From: Bilal, Haider Z (bilalhz at lsbu.ac.uk)
Date: Thu Oct 12 07:55:44 EDT 2006

Dear Matt and Danny,


Oh dear, I am really sorry, I have received Danny's email but have
missed it as I do get a lot of emails! I have had a flue since the
weekend and still trying to recover. I've been trying to work from my
bed, but not doing a good job :-(

I am not an expert programmer but I'm learning and I do appreciate
your detailed analysis and your time for helping. I will go through it
in detail and will reply back if you don't mind please.


Thank you very much.





Mr Haider Zuhair Bilal BEng MSc MIEE MIEEE MBCS

PhD Research Scholar

Centre for Systems and Software Engineering

Faculty of Business, Computing and Information Management

London South Bank University

103 Borough Road

London SE1 0AA



Tel: +44(0)20 7815 7473

Fax: +44(0)20 7815 7550

Mobile: +44(0)7887 598355





-----Original Message-----
From: Matt Jadud [mailto:mcj4 at kent.ac.uk] 
Sent: 11 October 2006 09:57
To: Bilal, Haider Z
Cc: Danny Yoo
Subject: [Fwd: Re: [plt-scheme] Scheme Program]


Hi Bilal,


Danny gave you a good, thoughtful reply just a few days ago. If you're

subscribed to the list, and you're asking questions to the list, you 

should watch for replies to your messages.


Danny has already outlined a number of steps you can take, and I

you take everything he said on-board. His advice is, in my experience,

usually quite good. When it isn't "quite good", it's bordering on 

"excellent". If that seems over-the-top, then I'll claim that the word

"thorough" always applies to the answers he provides on-list.





-------- Original Message --------

Subject: Re: [plt-scheme] Scheme Program

Date: Mon, 2 Oct 2006 14:29:16 -0700 (PDT)

From: Danny Yoo <dyoo at hkn.eecs.berkeley.edu>

To: Bilal, Haider Z <bilalhz at lsbu.ac.uk>

CC: plt-scheme at flux.utah.edu


<9FFEE39DADA4A442B06FB5673765F41002847F77 at CSD-EXBE-VS1.lsbu.ac.uk>


> However, this section of the code is not working properly and giving

> the following error: apply: bad procedure: #[undefined]


Hi Haider,


The following is a code review of the code.  Please don't take any of

comments as condemnation against your own person. I'll try to keep

criticism directed at the code.



Code review comments:


     * I tried reading your program.  I suppose I'm not be a Schemer

       but I think the program is, frankly, hard to read.  It's way

       nested for me to read comfortably, and the indentation is in

       that does not seem natural.  Double-spacing Scheme code is not



     * There are superfluous expressions.  Doing a test like:


           (not (equal? (pdg-vertex-ids-killed v) #f))


       can be more simply expressed as:


           (pdg-vertex-ids-killed v)


     * There's a LOT of mutation going on in the code.  Are you sure

       want to do that?  It's really making the code more complicated

       it needs to be.


     * There are subexpressions that basically look like big

       blocks.  Don't copy-and-paste: abstract!  Concretely, the only

       difference I see between


                   (if (pdg-vertex-ids-killed v)


                        (pdg-vertex-ids-killed v)

                        (lambda (y)



                                (file-get-line-num fileuid offset)))

                            (set! linelist

                                  (cons (list line-num y v)






                   (if (pdg-vertex-ids-used v)


                        (pdg-vertex-ids-used v)

                        (lambda (y)



                                (file-get-line-num fileuid offset)))

                            (set! linelist

                                  (cons (list line-num y v)




       is just one minor subexpression.


     * Everything seems to be stuffed in one gargantuan function.

       writing helper functions where it will clarify the code's


     * I see no direct use of APPLY in your code, so something else
must be

       calling it.  Actually, I see a few type errors in the code.


       Concretely: what's the "contract" of ABS-LOC-SET-TRAVERSE?

       your usages of that function: the code is definitely violating 

its use of

       ABS-LOC-SET-TRAVERSE in a few places.




You made the comment:


> However, it gave me wrong output, some had TO and FROM both listed 

> together:


What in the program prevents from happening? From the sequence of



     (if (pdg-vertex-ids-killed (caddr z))

         (abs-loc-set-traverse ...))

     (if (pdg-vertex-ids-used (caddr z))

         (abs-loc-set-traverse ...))


there's nothing in the code that excludes both PDG-VERTEX-IDS-KILLED

PDG-VERTEX-IDS-USED to return true values.



If you are going to write more Scheme code, you might also want to

consider doing a read-through a textbook like HTDP:




If you do so, your programs will tend to have a better design.




I've reformatted your code as best as I can in the context of a PLT

module, to be able to use the Syntax Check tool as well as better see

structure of the program.




(module pdg mzscheme

   ;; Unknown: the following definitions are here only so I can run

   ;; check syntax and see where values are coming from.

   (define (pdg-vertex-set-traverse l f) (void))

   (define (int-pair-set-traverse l f) (void))

   (define (abs-loc-set-traverse l f) (void))

   (define (pdg-vertices pdg) (void))

   (define (pdg-compilation-uid pdg) (void))

   (define (pdg-vertex-pdg pdg) (void))

   (define (pdg-kind pdg) (void))

   (define (pdg-vertex-charpos pdg) (void))

   (define (pdg-vertex-ids-killed pdg) (void))

   (define (pdg-vertex-ids-used pdg) (void))

   (define (file-get-line-num x y) (void))

   (define (sort l cmp) (void))

   (define (sdg-pdgs) (void))



   (define (assignments)


     (define filenumber 1)


     (define (process-pdg pdg)

       (when (eqv? (pdg-kind pdg) 'user-defined)

         (let* ((out-port


                  (string-append "Fun"

                                 (number->string filenumber)


                (linelist ()))


            (pdg-vertices pdg)

            (lambda (v)

              (let* ((fileuid


                       (pdg-vertex-pdg v))))


                 (pdg-vertex-charpos v)

                 (lambda (offset w)

                   (if (pdg-vertex-ids-killed v)


                        (pdg-vertex-ids-killed v)

                        (lambda (y)




                                 fileuid offset)))

                            (set! linelist

                                  (cons (list line-num y v)




                   (if (pdg-vertex-ids-used v)


                        (pdg-vertex-ids-used v)

                        (lambda (y)




                                 fileuid offset)))

                            (set! linelist

                                  (cons (list line-num y v)






           (set! linelist

                 (sort linelist

                       (lambda (a b)

                         (< (cadar a) (cadar b)))))


           (for-each (lambda (z)


                           ((linenum (car z)))

                         (define line-num (car z))

                         (display (cdr line-num) out-port)

                         (write-char #\tab out-port)


                         (if (pdg-vertex-ids-killed (caddr z))


                              (pdg-vertex-ids-killed (caddr z))

                              (display "to" out-port)))


                         (if (pdg-vertex-ids-used (caddr z))


                              (pdg-vertex-ids-used (caddr z))

                              (display "from" out-port)))


                         (newline out-port)))



           (close-output-port out-port))


         (set! filenumber (+ filenumber 1))))


     (for-each process-pdg (sdg-pdgs)))




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