Re: Working with constansts

[Barry Margolin <barmar@alum.mit.edu>]

In article <mailman.7052.1242121473.31690.help-gnu-emacs@gnu.org>,
 Nikolaj Schumacher <me@nschum.de> wrote:

> Richard Riley <rileyrgdev@googlemail.com> wrote:
> 
> >> Because this would incur overhead on every assignment, as it would have 
> >> to check whether the variable being assigned was declared as a constant.  
> >> Since this is so rarely the case, this overhead could be seen as mostly 
> >> wasted and unnecessary.
> >
> > I don't know enough about Lisp than I can only assume that in this case
> > it can not be detected at compile time IF you compile to byte/p code.
> 
> "Thanks" to dynamic scoping it cannot be caught at compile time.

It could at least generate a warning.

> (defconst xxx nil)
> 
> (defun change-xxx ()
>   (setx xxx t)) ;; const or variable?
> 
> (let ((xxx nil))
>   (change-xxx))

This should also warn about binding a constant.

-- 
Barry Margolin, barmar@alum.mit.edu
Arlington, MA
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