[plt-scheme] Side effect requiring rnrs/base-6?

Robby,

Yes I am sure, I copy pasted the exact code. Here are the screenshots  
for your reference. You can also verify the version information in the  
interactive console.

http://gallery.me.com/itsgg/100023/mac (No exception)
http://gallery.me.c…/itsgg/100023/linux1 (Exception)
http://gallery.me.c…/itsgg/100023/linux2 (Commented letrec block. No  
exception)

Cheers,
Ganesh Gunasegaran

On 17-Sep-2009, at 9:54 AM, Robby Findler wrote:

> Are you sure you ran exactly the same code and you were using exactly
> the same version? At that level, there is no difference between the
> two versions (ie, it is the same source code that implements cons
> etc).
>
> Robby
>
> On Wed, Sep 16, 2009 at 11:15 PM, Ganesh Gunasegaran
> <ganesh.gunas at gmail.com> wrote:
>> Hi Jens,
>>
>> Thanks for the explanation. Couple of questions
>>
>> - The same code doesn't throw the mcar exception in Mac OSX version  
>> of
>> DrScheme(4.2.1). The exception is thrown only in the linux version of
>> DrScheme(4.2.1).
>>
>> - Even in the linux version of DrScheme, the exception is not  
>> thrown if I
>> comment the unrelated letrec block.
>>
>> Even if shadowing occurs as you suggested, there is inconsistency  
>> across
>> operating systems.
>>
>> Cheers,
>> Ganesh Gunasegaran.
>>
>> #lang scheme
>> (require rnrs/base-6)
>>
>> (letrec ([my-sum (lambda (l)
>>            (if (null? l)
>>                0
>>                (+ (car l) (my-sum (cdr l)))))])
>>  (my-sum '(1 2 3 4)))
>>
>> (define my-sum
>>  (lambda (l)
>>   (if (null? l)
>>       0
>>       (+ (car l) (my-sum (cdr l))))))
>>
>>
>> On 16-Sep-2009, at 11:29 PM, Jens Axel Søgaard wrote:
>>
>>> 2009/9/16 Jens Axel Søgaard <jensaxel at soegaard.net>:
>>>>
>>>> [sent privately too by accident]
>>>>
>>>> 2009/9/16 Ganesh Gunasegaran <ganesh.gunas at gmail.com>:
>>>>>
>>>>> Hi All,
>>>>>
>>>>> I am very new to Scheme
>>>>>
>>>>> What is wrong with the following code?
>>>>>
>>>>>
>>>>> --------------------------------------------------------------------------------------------------------------------------------
>>>>> #lang scheme
>>>>> (require rnrs/base-6)
>>>
>>> One more thing:
>>>
>>> Since the entire rnrs/base-6 is required some functions from  
>>> "scheme"
>>> such as car, cdr, cons are shadowed by their bindings in rnrs/ 
>>> base-6.
>>> In particular in rnrs the identifier car is bound to the same value
>>> as the identifier mcar is bound to in "scheme'. That is, after the
>>> require line, when you write "car" you are actually calling "mcar".
>>>
>>> This might we somewhat confusing, for new Scheme users, so
>>> here is a practical advise:
>>>
>>> Stick either to the "scheme" language, and if you need a particular
>>> function from rnrs use the documentation to figure out, what
>>> is called in PLT Scheme (in 99% of the cases the names
>>> are the same).
>>>
>>> --
>>> Jens Axel Søgaard
>>
>> _________________________________________________
>>  For list-related administrative tasks:
>>  http://list.cs.brown.edu/mailman/listinfo/plt-scheme
>>

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