Doesn't really answer your question, but why not use something like this
instead:
(define inc
(let ((counter 0))
(lambda ()
(set! counter (add1 counter))
counter)))
Best,
Erich
On Mon, 2011-10-31 at 12:58 -0400, jkaczo...@aol.pl wrote:
> Hi,
>
> I’m using DrRacket.
> In an edit window I have written:
>
> #lang racket
> (define counter 0)
>
> I’m pressing “Run” button and next, in a command line, after running a
> command:
>
> (set! counter (add1 counter))
>
> I receive a message “set!: cannot modify a constant: counter”
>
> The problem can be resolved by changing the language (Language/Choose
> language/R5RS and unchecking “Disallow redefinition of initial
> binding”) but I suppose that in this way I can lose an access to the
> racket libraries.
> Of course, I realize, that redefinition of the variables is not good
> (functional) programming style but sometimes it’s necessary. Is there
> a possibility of such modifications without changing language?
>
> Jerzy
>
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