[racket] testing impure stuff

I'll add support for an optional directory-filtering function to
`in-directory`.

At Tue, 24 Dec 2013 05:24:50 +0100, Manfred Lotz wrote:
> On Mon, 23 Dec 2013 20:51:16 -0600
> Robby Findler <robby at eecs.northwestern.edu>
> wrote:
> 
> > I don't think the proposed fix would "resist" in this manner. The
> > directory could be deleted between the time you check for its
> > existence and when you ask for its contents.
> > 
> 
> I would differentiate between static and dynamic errors.
> 
> Static error is that a directory couldn't be traversed because of
> permission denied. An optional parameter would do.
> 
> Dynamic error is that during traversing a bad thing happens.
> Permissions gets changed or even the directory gets deleted. In this
> case it is an exception, and in-directory stops. However, the issuer of
> in-directory should have an option to resume.
> 
> 
> -- 
> Manfred
> 
> 
> 
> > 
> > 
> > On Mon, Dec 23, 2013 at 7:05 PM, Matthias Felleisen
> > <matthias at ccs.neu.edu>wrote:
> > 
> > >
> > > If you don't have permissions, you can't recur and the current
> > > implementation throws an error w/o recourse to a fix. As Manfred
> > > points out, this is a 'fair weather' function. A real
> > > implementation should resist such external mishaps. But I also
> > > agree w/ you about the parameter. It would generalize this
> > > situation -- Matthias
> > >
> > >
> > >
> > >
> > >
> > >
> > > On Dec 23, 2013, at 5:53 PM, Robby Findler wrote:
> > >
> > > Perhaps in-directory can take an optional parameter that controls
> > > whether or not to recur?
> > >
> > > Robby
> > >
> > >
> > > On Mon, Dec 23, 2013 at 4:42 PM, Matthias Felleisen
> > > <matthias at ccs.neu.edu>wrote:
> > >
> > >>
> > >> On Dec 23, 2013, at 5:12 PM, Manfred Lotz
> > >> <manfred.lotz at arcor.de> wrote:
> > >>
> > >> > I think in-directory should be fixed in the long run.
> > >>
> > >> Agreed. -- Matthias
> > >>
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> > >
> > >
> > >
> > 
> 
> 
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