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From: Emiliano <emiliano@example.invalid>
Newsgroups: comp.lang.tcl
Subject: Re: Are class consts possible?
Date: Sat, 21 Jun 2025 14:03:33 -0300
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On Fri, 20 Jun 2025 07:58:37 -0000 (UTC)
Mark Summerfield <m.n.summerfield@gmail.com> wrote:

> Is it possible to create class-specific consts i.e., consts that exist 
> inside a class's namespace?
> 
> For example, this does _not_ work:
> 
> ```
> 
>     oo::class create Klass {
>         const SPECIAL special
> 
>         method say {} { return $SPECIAL }
>     }
> 
>     set klass [Klass new]
>     puts "$Klass::SPECIAL [$klass say]"
> 
> ```

Maybe there are more straightforward methods, but this one works:

% oo::class create C {
    method foo {} { # reads the constant
        classvariable CVar
        puts $CVar
    }
    method bar {} { # tries to set the constant
        classvariable CVar
        set CVar "other value"
    }
}
::C
% namespace eval [info object namespace C] {
    # defines the constant in the class namespace
    const CVar "My class variable"
}
% C create o
::o
% o foo
My class variable
% o bar
can't set "CVar": variable is a constant


Regards
-- 
Emiliano