[plt-scheme] (no subject)

From: Geoffrey S. Knauth (geoff at knauth.org)
Date: Sat Mar 17 11:29:13 EDT 2007

Hello Patrick, isn't MIT OCW wonderful?

I tried your program in the Beginning Student language of DrScheme,  
and it worked fine:

(define (area-of-disk r)
   (* pi (* r r)))

(define (area-of-ring outer inner)
   (- (area-of-disk outer)
      (area-of-disk inner)))

After you input a program in the definitions pane, you should save  
it--I used the filename "disk-geometry.scm"--and then press the Run  
button.  In the interactions pane, this is what I got:

Welcome to DrScheme, version 360.
Language: Beginning Student.
Teachpack: /Applications/Added_Apps/PLT_Scheme/collects/teachpack/ 
 > (area-of-ring 6 4)

Geoffrey S. Knauth | http://knauth.org/gsk

On Mar 17, 2007, at 04:01, Pat wrote:
> Hi guys, I am a freshman student in Kenya. After I stumbled on  
> MIT's ocw website, I got interested in Scheme and after a few while  
> on this LtU site, I felt like starting with DrScheme is the best  
> way since its tailoured to the biginners. I am very new in  
> Programming and we just don't have great teachers who have command  
> of the subject here in Kenya.
> Well after installing and running DrScheme, I encountered a problem  
> which I will be very greatful to anyone of you who can help.
> I difined this procedure: (define (area-of-disk r)
> (* 3.14 (* r r)))
> which worked when I ran it like this (area-of-disk 5)
> then I defined this: (define (area-of-ring outer inner)
> (- (area-of-disk outer)
> (area-of-disk inner)))
> However upon running this procedure I got this message; area-of- 
> disk: name is not defined, not an argument, and not a primitive name.
> and this on the tracing window: No tracing results are available,  
> yet. (Make sure that your language supports tracing and that  
> tracing is enabled.)
> Can anyone help?
> -- 
> Live, Learn, Love!
> Patrick Amkayah.

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