[plt-scheme] Re: sxml.ss - Works on its own, but not in module

From: Eli Barzilay (eli at barzilay.org)
Date: Wed Jan 16 15:22:38 EST 2008

On Jan 16, John Clements wrote:
> On Jan 16, 2008, at 12:52 AM, Dmitry Lizorkin wrote:
> > Hello John
> >
> >> it's also sort of a problem with the sxml package, AFAICT.
> >
> > I agree with you completely.
> >
> >> Would it be possible to fix the package so that this is no longer  
> >> an issue?
> >
> > I would be willing to fix this; however, I need your hint on how to  
> > handle such an eval-inside-a-package-issue in PLT module system.
> I believe that the canonical answer is: this use of eval is
> untenable in PLT Scheme.  In particular, I observe that in PLT v4
> (more specifically, that I cannot compile your "foo.ss"
> file, because I get an error that bar:f is unbound, which is pretty
> much what I'd expect.  I'm willing to believe that this code works
> differently in version 371.

FWIW, 3.99 allows using eval in a much saner way (IMO):

  #lang scheme/base
  (define (bar:f) 1)
  (define-namespace-anchor bar-world)
  (define (bar:g) (eval '(bar:f) (namespace-anchor->namespace bar-world)))
  (provide (all-defined-out))

  #lang scheme/base
  (require "bar.ss")
  (define test (bar:g))
  (provide test)

  Welcome to MzScheme v3.99.0.9 [3m], Copyright (c) 2004-2008 PLT Scheme Inc.
  > (require "foo.ss")
  > test

          ((lambda (x) (x x)) (lambda (x) (x x)))          Eli Barzilay:
                  http://www.barzilay.org/                 Maze is Life!

Posted on the users mailing list.