[Scilab-users] Variable scope in Scilab

[Stéphane Mottelet]

Hi Frederico,

I do not have any problem with the variable scoping in Scilab and as I 
said before, even in Julia there is a similar scoping (at least for the 
particular case of functions). However, the status of formal input and 
output parameters should prevent the scoping to apply to them. For 
example, the following does also work (as an addition to my previous 
example for the input parameter):

function y=f(x)
endfunction

y=1
f

-> f
  ans  =

    1.

Frankly speaking, allowing such a behavior is madness...

S.

Le 27/02/2021 à 01:33, Federico Miyara a écrit :
>
> Stéphane,
>
> I agree it shouldn't happen, but the same moment access to outer 
> variables is granted you can't prevent such thing to happen since 
> inside the function all variables have a name which is more than just 
> a symbol or a mute variable, and this includes undefined arguments.
>
> This scoping feature is dangerous and I don't think it would be 
> advisable to create a macro for general use exploiting it.
>
> May be someone can provide an example where it has been used with 
> profit or explain why it was originally introduced
>
> Regards,
>
> Federico Miyara
>
> On 26/02/2021 10:38, Stéphane Mottelet wrote:
>> Hi all,
>>
>> In Scilab the scope of variables is quite permissive but even in 
>> Julia (really strict rules) we can have the following behavior:
>>
>> function y=f(x)
>>  y=x+a;
>> end
>>
>> a=1;
>> f(2)
>> a=2;
>> f(3)
>>
>> -> a=1;
>>
>> --> f(2)
>>  ans  =
>>
>>    3.
>>
>> --> a=2;
>>
>> --> f(3)
>>  ans  =
>>
>>    5.
>>
>> Yesterday afternoon I was my students for a Scilab beginners 
>> tutorial, and by accident one of them had "x" defined before in the 
>> main workspace and tried to call f without arguments. I reproduce the 
>> experiment here by explicitely defining x before the call:
>>
>> x=1;
>> f
>>
>> --> x=1;
>>
>> --> f
>>  ans  =
>>
>>    3.
>>
>> Allowing the function inner scope to see variables of the outer scope 
>> is one thing, you may or may not agree this is not the point here, 
>> but allowing to call f without arguments just because the formal 
>> input parameter has the same symbol as an outer scope symbol is 
>> another thing. I knew this was possible even if i never used such a 
>> feature, but my students were so puzzled by this, particularly those 
>> who already learned other low-level languages, that I decided to 
>> propose the suppression of this, that I consider as a serious 
>> potential source of many bugs. Don't tell me that this would break 
>> some user code because I frankly have no consideration for this kind 
>> of crappy shortcut and, sorry if it may sound rude, for programmers 
>> who use it...
>>
>> S.
>>
>
>
> <https://antispam.utc.fr/proxy/2/c3RlcGhhbmUubW90dGVsZXRAdXRjLmZy/www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient> 
> 	Libre de virus. www.avast.com 
> <https://antispam.utc.fr/proxy/2/c3RlcGhhbmUubW90dGVsZXRAdXRjLmZy/www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient> 
>
>
> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
>
> _______________________________________________
> users mailing list
> users at lists.scilab.org
> https://antispam.utc.fr/proxy/1/c3RlcGhhbmUubW90dGVsZXRAdXRjLmZy/lists.scilab.org/mailman/listinfo/users

-- 
Stéphane Mottelet
Ingénieur de recherche
EA 4297 Transformations Intégrées de la Matière Renouvelable
Département Génie des Procédés Industriels
Sorbonne Universités - Université de Technologie de Compiègne
CS 60319, 60203 Compiègne cedex
Tel : +33(0)344234688
http://www.utc.fr/~mottelet

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.scilab.org/pipermail/users/attachments/20210301/4e614a4a/attachment.htm>