[Scilab-Dev] [Scilab-users] Variable scope in Scilab

[Stéphane Mottelet]

Hi devs,

Just after changing the rule in macro.cpp I see this at startup, and I 
am laughing out loud ;-)

Scilab branch-6.1 (Feb 19 2021, 14:37:51)
at line    44 of function mdelete            ( 
/Users/mottelet/git/scilab_6.1.orig/scilab/modules/fileio/macros/mdelete.sci 
line 57 )
at line    26 of function atomsAUWriteAccess ( 
/Users/mottelet/git/scilab_6.1.orig/scilab/modules/atoms/macros/atoms_internals/atomsAUWriteAccess.sci 
line 42 )
at line    11 of function atomsSystemInit    ( 
/Users/mottelet/git/scilab_6.1.orig/scilab/modules/atoms/macros/atomsSystemInit.sci 
line 27 )

Wrong number of input arguments.

-->

Does it mean that we use the "crappy shortcut" as a feature in Scilab 
internals ?

S.

Le 26/02/2021 à 14:38, Stéphane Mottelet a écrit :
> 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.
>
-- 
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