[racket] Am I Missing Something? [HtDP 31.3.1]

From: Carl Eastlund (cce at ccs.neu.edu)
Date: Tue Jan 4 15:26:49 EST 2011

Richard,

We're not looking for an explanation of why the two numbers are
different.  We're looking for an explanation of why, on Luke's
machine, unlike anybody else's here, they _aren't_ different.  Somehow
I don't think portability issues in DrRacket are anybody's homework
assignment.  So if you have an explanation, please share.  :)

Carl Eastlund

On Tue, Jan 4, 2011 at 3:22 PM, Richard Cleis <rcleis at mac.com> wrote:
> I can explain it, but I don't know if it's revealing a solution.
>
> rac
>
> On Jan 4, 2011, at 12:32 PM, Stephen Chang wrote:
>
>> I get results similar to Carl.
>>
>> Welcome to DrRacket, version 5.0.1.7 [3m].
>> Language: Intermediate Student.
>> #i-0.49746596003269394
>> #i-0.4974659600326953
>> #i-4974659600326939.0
>> #i-4974659600326953.0
>>> (equal? (sum (g-series #i1000)) (accu-sum (g-series #i1000)))
>> false
>>> (equal? (* 10e15 (sum (g-series #i1000))) (* 10e15 (accu-sum (g-series #i1000))))
>> false
>>>
>>
>>
>> Luke, can you post the output you get?
>>
>>
>>
>>
>> On Tue, Jan 4, 2011 at 10:57 AM, Carl Eastlund <cce at ccs.neu.edu> wrote:
>>>
>>> On Tue, Jan 4, 2011 at 9:38 AM, Luke Jordan <luke.jordan at gmail.com> wrote:
>>>> All that code came straight out of the text, except that I used if instead
>>>> of cond.  The sum, accu-sum, and g-series defs are all given.  In your
>>>
>>> Ah, yes, now I see where the accumulator-based sum is.  Sorry, my mistake.
>>>
>>>> results I see a difference.  When I run it at home it's the same.  I can
>>>> even (equal? (sum (listof number)) (accu-sum (listof number))) and get true.
>>>
>>> No idea what's going on.  Maybe someone else will have an idea.
>>>
>>> --Carl


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