[racket] Creating a #lang language, and modifying contract system

Don't apologize, I'm very grateful for your help :-)
I'll take a look at the paper and the documentation

Cheers

2011/8/11 Robby Findler <robby at eecs.northwestern.edu>

> Well, continuation-marks are a lower-level, lighter-weight construct
> than parameters.
>
> Sometimes you have to use parameters because that's the api you get to
> work with (current-output-port being a popular example of that) and
> sometimes you have to use continuation-marks because that's the api
> you get to work with (the exn field that you're using, altho this is a
> much rarer case).
>
> Featurewise, parameters have guards, they work with parameterizations,
> they can be set directly (as opposed to stored as part of a
> continuation) and they behave differently write to the interactions
> with threads. Continuation marks don't do any of that.
>
> Overall, I guess, the best answer is "it depends" and I'm sorry to say
> it, but I think that your best bet is to study the constructs yourself
> to try to understand them.
>
> Matthew recently wrote an excellent note about the interactions with
> eval and namespaces and why you should or shouldn't use one and I
> would love to be able to provide you with the same, but I don't have
> such an essay yet. I'm sorry. The best I can offer you is the
> documentation and this paper:
>
>  http://www.eecs.northwestern.edu/~robby/pubs/papers/icfp2007-fyff.pdf
>
> I apologize in advance if this is too researchy for what you're looking
> for.
>
> Perhaps others have more practical experience and would like to chime in.
>
> Robby
>
> On Thu, Aug 11, 2011 at 8:55 AM, Ismael Figueroa Palet
> <ifigueroap at gmail.com> wrote:
> > I'll try that in my particular case, however, what is the main difference
> > and how do I decide whether to use continuation marks or parameters??
> what
> > are the advantages/disadvantages of choosing one over the other?
> > Thanks
> >
> > 2011/8/10 Robby Findler <robby at eecs.northwestern.edu>
> >>
> >> A parameter is implementing using continuation marks (and other things).
> >>
> >> The short version of the story is that you want to say
> >>
> >>  (with-continuation-mark 'key 'value e)
> >>
> >> instead of
> >>
> >>  (parameterize ([param 'value]) e)
> >>
> >> and then when the exception is raised, you'll find that it has a field
> >> that holds the continuation marks in effect at the point where the
> >> value was raised. You can then use that to extract the 'value you
> >> stored with the 'key.
> >>
> >> There is more information in the manuals about these primitives that
> >> you'll want to read but don't hesitate to ask if you get stuck.
> >> (Overall, it sounds like it should be much easier to use this approach
> >> than the one you were thinking of before.)
> >>
> >> Robby
> >>
> >> On Wed, Aug 10, 2011 at 11:25 AM, Ismael Figueroa Palet
> >> <ifigueroap at gmail.com> wrote:
> >> > Hi again Robby,
> >> > I really don't know much about continuation marks. I want the value A
> to
> >> > be
> >> > embedded on the exception structure, because I check that value with a
> >> > modified with-handlers macro. I thought that using parameters A will
> >> > behave
> >> > like a dynamically scoped identifier.
> >> > What are the differences, if any, of using continuation marks versus
> >> > using
> >> > parameters??
> >> > Thanks
> >> >
> >> > 2011/8/9 Robby Findler <robby at eecs.northwestern.edu>
> >> >>
> >> >> Could you put the value into a continuation mark and then, when you
> >> >> catch the exception, look in the continuation marks to get it out
> >> >> again?
> >> >>
> >> >> Robby
> >> >>
> >> >> On Tue, Aug 9, 2011 at 3:56 PM, Ismael Figueroa Palet
> >> >> <ifigueroap at gmail.com> wrote:
> >> >> >
> >> >> >
> >> >> > 2011/8/9 Robby Findler <robby at eecs.northwestern.edu>
> >> >> >>
> >> >> >> On Tue, Aug 9, 2011 at 3:01 PM, Ismael Figueroa Palet
> >> >> >> <ifigueroap at gmail.com> wrote:
> >> >> >> > 2011/8/4 Robby Findler <robby at eecs.northwestern.edu>
> >> >> >> >>
> >> >> >> >> The blame assignment stuff is wired pretty deep into the
> contract
> >> >> >> >> system. There isn't currently any way to change that aspect of
> >> >> >> >> the
> >> >> >> >> system without doing what you've done below.
> >> >> >> >>
> >> >> >> >> If you can say more about how/why you want to change it, tho,
> >> >> >> >> there
> >> >> >> >> maybe some extension to the current API that would work for you
> >> >> >> >> and
> >> >> >> >> that we'd be willing to maintain going forward.
> >> >> >> >
> >> >> >> > I defined a new-exn struct to represent exceptions and defined a
> >> >> >> > raise
> >> >> >> > macro
> >> >> >> > that wraps Racket's raise to throw a new-exn value. Also, I need
> >> >> >> > to
> >> >> >> > raise
> >> >> >> > the exception thrown by raise-blame-error inside a parameterize
> >> >> >> > expression.
> >> >> >> > I want to access and modify a parameter that will be used to
> >> >> >> > construct
> >> >> >> > the
> >> >> >> > new-exn value.
> >> >> >>
> >> >> >> It sounds like you're maybe adding a field to the exn record? Can
> >> >> >> you
> >> >> >> say more about what that field is and how you compute its value?
> (Or
> >> >> >> if I'm just wrong about that?)
> >> >> >
> >> >> > Yes, the end result I want is to tag the exn record with a value.
> >> >> > That
> >> >> > value
> >> >> > is stored in a parameter A. I want to make raise-blame-error to
> >> >> > always
> >> >> > raise
> >> >> > an exception tagged with A+1.
> >> >> >
> >> >> > --
> >> >> > Ismael
> >> >> >
> >> >> >
> >> >
> >> >
> >> >
> >> > --
> >> > Ismael
> >> >
> >> >
> >
> >
> >
> > --
> > Ismael
> >
> >
>



-- 
Ismael
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