Re: [TCLCORE] TIP #184: Avoid Creating Unusable Variables

[miguel s. <mi...@ut...>]

Larry Smith wrote:
> 
>>  One example is:
>>       upvar 0 x(1) y(1)
>>
>>  which creates a /scalar/ variable named y(1) that is linked to the 
>>  element 1 of the array x. However, there is no way for a tcl script 
>> to  read or write such scalar variables, the parser will interpret 
>> that  name as referring to an element of the array named y. 
> 
> 
> % global x(1)
> % set {x(1)} foo
> foo
> % puts ${x(1)}
> foo
> 
> 
> 

% proc a {} {
     global x(1)
     set {x(1)} foo
     foreach n [info vars] {
         catch {append res "$n: [set $n]"}
     }
     puts $res
     info vars
}
% a
x(1): foo
n res x x(1)
% info vars x*
x
% set x(1)
can't read "x(1)": no such element in array

What happened is: a managed to set the element 1 of the local array x to 
"foo", but NOT the local scalar variable 'x(1)' to foo. The latter is 
the one that was linked to element 1 of the global array x.