[plt-scheme] let vs parameterize?

Oh! Custodians are the mechanism we use to identify "principal"s for
the purpose of reclaiming resources. Threads are one such resource.

I suggest that you read these two papers to get an idea of the
pragmatics of custodians:

  http://www.ccs.neu.edu/scheme/pubs/icfp99-ffkf.pdf
  http://www.cs.utah.edu/plt/publications/pldi04-ff.pdf

They are really quite different than the other things (let, fluid-let,
parameterize) you are asking about.

Robby

On 4/16/07, Yin-So Chen <yinso.chen at gmail.com> wrote:
> They are both mentioned under the thread chapter in mzscheme doc hence I
> thought they were related ;)  Under what situation do I need to think about
> custodians?
>
> Thanks,
> yinso
>
>
>  On 4/16/07, Robby Findler <robby at cs.uchicago.edu> wrote:
> > No, parameterize doesn't use custodians. They're independent of each
> other.
> >
> > Robby
> >
> > On 4/16/07, Yin-So Chen <yinso.chen at gmail.com> wrote:
> > > Thanks Robby/Carl (and Eric for answering privately) -
> > >
> > > here's a related question:  Does parameterize automatically uses a
> custodian
> > > (e.g. current-custodian) to manage resources or custodians have to be
> used
> > > explicitly?
> > >
> > >
> > > On 4/16/07, Robby Findler < robby at cs.uchicago.edu> wrote:
> > > > Another difference between parameters and fluid-let: in a fluid-let
> > > > the values are not thread local, but in a parameter they are.
> > > >
> > > > Robby
> > > >
> > > > On 4/16/07, Carl Eastlund <cce at ccs.neu.edu > wrote:
> > > > > On 4/16/07, Yin-So Chen < yinso.chen at gmail.com> wrote:
> > > > > > What is the difference between using let vs parameterize?
> > > > >
> > > > > Let operates on bindings.  It creates a new name and binds it to a
> > > > > value.  This affects code directly within the let-body that refers
> to
> > > > > the same name, providing it is not bound again ("shadowed") inside
> the
> > > > > let.
> > > > >
> > > > > Parameterize operates on parameters, which are values.  It takes an
> > > > > existing parameter and makes it return a different value during the
> > > > > execution of the body of the parameterize.  This affects any code
> > > > > called during that execution, even if it's in a different function,
> > > > > module, whatever, so long as it uses the same parameter value.
> > > > >
> > > > > > It seems that one can use let to manipulate parameter objects (at
> > > least
> > > > > > scheme doesn't forbid it) - any issues with using it?
> > > > >
> > > > > Let does not manipulate values at all.  It just binds names to
> > > > > existing values.  It never changes values or their contents.
> > > > >
> > > > > >  How do I know whether or not something is a parameter versus a
> > > variable?
> > > > >
> > > > > You could ask the same thing about numbers vs variables, or strings
> vs
> > > > > variables.  A variable is a name for a value.  That value might be
> > > > > anything: number, string, list, parameter, etc.  But you should be
> > > > > careful never to confuse the name with what it refers to.
> > > > >
> > > > > And in response to the followup email: fluid-let, like let, operates
> > > > > on variables (names), not values.  Hence it would not be an
> > > > > "extension" to make it work on parameters.  If you give the name of
> a
> > > > > parameter to fluid-let, it will change which parameter that name
> > > > > refers to, not the contents of the current parameter.
> > > > >
> > > > > --
> > > > > Carl Eastlund
> > > > > _________________________________________________
> > > > >   For list-related administrative tasks:
> > > > >
> http://list.cs.brown.edu/mailman/listinfo/plt-scheme
> > > > >
> > > >
> > >
> > >
> > >
> > > --
> > > http://www.yinsochen.com
> > > ...continuous learning...
> >
>
>
>
>  --
>
> http://www.yinsochen.com
> ...continuous learning...