[BULK] [plt-scheme] Teaching Scheme

Dear Shriram,

In an effort to be equivalent to all the other implementations, it would be great to write the values to stdout in the same format.

If this isn't possible with Scheme, thats fine, but it might be considered a weakness. Lots of people want to print something out, either for debugging purposes or simply to see intermediate results of processing. It is a very common way of teaching programming at present. 

This might not be the best way to debug Scheme (I'm not a Scheme programmer) but if this is the case then it will be important to discuss this on the page about Scheme, especially as a potential reason why someone would want to use Scheme.

Kind regards,
Samuel

On 4/05/2010, at 2:31 AM, Shriram Krishnamurthi wrote:

> Functions compute values.  They don't print output.
> 
> On Mon, May 3, 2010 at 7:26 AM, Samuel Williams
> <space.ship.traveller at gmail.com> wrote:
>> Dear Stephen,
>> Can you let me know firstly which function is responsible for printing the
>> output?
>> Secondly, can you add comments explaining how it works? I can generally
>> appreciate what you are doing, but I'm not a Scheme programmer so I might
>> not understand the exact detail correctly.
>> Thanks
>> Samuel
>> On 4/05/2010, at 1:01 AM, Stephen Bloch wrote:
>> 
>> Well, that particular algorithm relies very heavily on mutation, but here's
>> a functional version.
>> (define (door-open door)
>>   (doh door 99))
>> (define (doh door pass)
>>   (cond [(zero? pass) true]
>>         [(= (remainder door (+ pass 1)) pass)
>>          (not (doh door (- pass 1)))]
>>         [else
>>          (doh door (- pass 1))]))
>> (define doors (build-list 100 door-open))
>> 
>> 
>> Somewhat shorter but more cryptic:
>> (define (door-open door)
>>   (doh door 99))
>> (define (doh door pass)
>>   (or (zero? pass)
>>       (not (boolean=? (= (remainder door (+ pass 1)) pass)
>>                       (doh door (- pass 1))))))
>> (define doors (build-list 100 door-open))
>> 
>> 
>> Even shorter, but takes some math (and illustrates how artificial this
>> problem is :-) :
>> (define (door-open door)
>>    (integer? (sqrt (+ door 1))))
>> (define doors (build-list 100 door-open))
>> 
>> 
>> Stephen Bloch
>> sbloch at adelphi.edu
>> 
>> 
>> 
>> 
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