[racket] testing impure stuff

On Mon, 23 Dec 2013 16:44:03 -0500
Matthias Felleisen <matthias at ccs.neu.edu>
wrote:

> 
> Sadly, I think you may have to re-implement in-directory (with a
> recursive traversal like the one in for.rkt) but use
> file-or-directory-permission before you try to go into a
> subdirectory. -- Matthias
> 
> 
> 

Yep, I did it like this:

(define (can-read-directory? d)
    (if (member 'read (file-or-directory-permissions d))
        #t
        (begin (display "Permission denied for ")
               (displayln d)
               #f)))


and in in-directory:

 (when (and (directory-exists? fp)
            (can-read-directory? fp))
     (loop fp p)))))


Perhaps not the smartest way but it works fine now:


I think in-directory should be fixed in the long run.



-- 
Manfred



> On Dec 23, 2013, at 4:09 PM, Manfred Lotz
> <manfred.lotz at arcor.de> wrote:
> 
> > I had a look into collects/racket/private/for.rkt where
> > in-directory is defined.
> > 
> > I have to admit that I don't understand much of the stuff as this
> > is a level of Racket I haven't yet mastered.
> > 
> > Nevertheless, there is 
> >       (when (directory-exists? fp)
> >          (loop fp p)))))
> > 
> > Here it should be checked if there is permission to read fp. Not
> > quite sure what is the best way to handle it. Issue an error
> > message and continue, or let the issuer of in-directory decide what
> > to do. 
> > 
> > In my case I copied the stuff into my own source, renamed it,
> > checked permissions and issue a message if there is no permission
> > to read and continue. Seems to be the solution for me for the time
> > being.
> > 
> > 
> > 
> > -- 
> > Manfred
> > 
> > 
> > 
> > On Mon, 23 Dec 2013 15:20:32 -0500
> > Matthias Felleisen
> > <matthias at ccs.neu.edu> wrote:
> > 
> >> 
> >> For that, you will need to wrap the whole loop because
> >> (in-directory ...) fails, and no, I don't know how to resume this
> >> optimized loop: 
> >> 
> >> #lang racket ;; foo.rkt 
> >> 
> >> (define start-dir ".")
> >> 
> >> ;;
> >> (with-handlers (((lambda (x) #t) (lambda (e) (log-warning
> >> "in-directory failed")))) (for ([f (in-directory start-dir)] #:when
> >> (regexp-match #rx"\\.rkt" f)) (with-handlers ((exn:fail:contract?
> >> (lambda (e) (log-warning (exn-message e)))) (exn? displayln))
> >>      (displayln (path->string f)))))
> >> 
> >> 
> >> 
> >> On Dec 23, 2013, at 3:06 PM, Manfred Lotz
> >> <manfred.lotz at arcor.de> wrote:
> >> 
> >>> #lang racket ;; foo.rkt 
> >>> 
> >>> (define start-dir "/tmp/testdir")
> >>> 
> >>> (for ([f (in-directory start-dir)] #:when (regexp-match
> >>> #rx"\\.rkt" f)) (with-handlers ((exn:fail:contract? (lambda (e)
> >>> (log-warning (exn-message e))))) 
> >>> (displayln (path->string f))))
> >> 
> >> 
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> > 
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