<html> <head> <style></style> </head> <body class='hmmessage'> <div> </div><div>Yeah that sounded "too good" to be true, as I was pretty sure to have read here that eval cannot have access at all to the enclosing bindings.</div> > Date: Tue, 20 Apr 2010 11:16:22 -0500 > Subject: Re: [plt-scheme] eval & syntax-rules > From: robby@eecs.northwestern.edu > To: skeptic2000@hotmail.com > CC: plt-scheme@list.cs.brown.edu > > This expression: > > (let ([t 2]) > (eval t (make-base-namespace))) > > is equivalent to this one: > > (eval 2 (make-base-namespace)) > > I think you probably meant to write this: > > (let ([t 2]) > (eval 't (make-base-namespace))) > > Eval is not what you think it is, I'd say. It isn't like ruby's eval, > for example. There are lots of discussions of this in the mail > archives for this list and some of them may even have made it into the > Guide. > > Robby > > On Tue, Apr 20, 2010 at 11:13 AM, Skeptic . <skeptic2000@hotmail.com> wrote: > > > > Hi, > > Why something like this works : > > #lang scheme > > (define t 9) > > (let ([t 2]) > >     (eval t (make-base-namespace))) > > -> 2 > > but not something like this : > > #lang scheme > > (define a 4) > > (define b 5) > > (define c 6) > > (define-syntax test > >   (syntax-rules () > >     [(test id ...) > >      (eval '(id ...) (make-base-namespace))])) > > (test a b c) > > ->  reference to a unidentified identifier : a > > Thanks. > > ________________________________ > > Gardez le contact. Obtenez la version mobile de Messenger ici > > _________________________________________________ > >  For list-related administrative tasks: > >  http://list.cs.brown.edu/mailman/listinfo/plt-scheme > > > > <hr />Messenger sur votre téléphone = MI sur la route <a href='http://go.microsoft.com/?linkid=9724469' target='_new'>Essayez-le maintenant.</a></body> </html>