[plt-scheme] How to make a setter out of an identifier

That's much simpler than I suggested ):
Jos


----- Original Message ----- 
From: "Robby Findler" <robby at eecs.northwestern.edu>
To: "Cheng-Chang Wu" <chengchangwu at yahoo.com>
Cc: <plt-scheme at list.cs.brown.edu>
Sent: Wednesday, November 04, 2009 2:34 AM
Subject: Re: [plt-scheme] How to make a setter out of an identifier


How about this:

(define-syntax-rule (make-setter kk) (lambda (x) (set! kk x)))

Robby

2009/11/3 Cheng-Chang Wu <chengchangwu at yahoo.com>:
> Hi,
>
> I am new to the brave scheme world, and trying hard to understand the secrets of macro.
>
> I want to do the following: take an identifier and make a setter out of the identifier.
>
> For example,
>
> (define kk 0)
> (make-setter kk)
>
> should give me a set-kk! which can be used to set the value of kk.
>
> The best macro I can image is
>
> (define-syntax make-setter
> (lambda (x)
> (syntax-case x ()
> ((make-setter id)
> (with-syntax
> ((def
> (datum->syntax
> (syntax k)
> `(define (,(string->symbol (string-append "set-" (symbol->string 'id) "!")) a-value) (set! id a-value)))))
> (syntax def))))))
>
>
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