Disallowing Specific Functions

It would be handy to be able to set! a function such as reverse to an expression which raises an error in a module. PLT Scheme does not allow this. However, it provides a different way through a module provide to export a binding as a different name than the one inside of the module itself: rename-out.

The following code illustrates how to bar a particular tested file from using reverse or append; note, however, that this will not autodetect if the students themselves implement such a function, and so hand-checking will still likely be necessary.

#lang scheme

(provide (rename-out (d-reverse reverse))
         (rename-out (d-append append)))

(define-syntax disallow
  (syntax-rules ()
    ((~ func)
     (lambda args
       (error (format "Disallowed function ~a called" (quote func)))))))

(define d-reverse (disallow reverse))
(define d-append  (disallow append))

-- TerryVaskor - 12 Mar 2009

Topic revision: r2 - 2010-02-17 - BobCui
 
This site is powered by the TWiki collaboration platform Powered by PerlCopyright © 2008-2015 by the contributing authors. All material on this collaboration platform is the property of the contributing authors.
Ideas, requests, problems regarding TWiki? Send feedback

escort ankara escort beylikduzu escort istanbul escort eskisehir escort bursa