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

I think it would work, more or less. However, I think that if "someone"
change the parameter only and not update the continuation mark (either by
mistake, malice, or other reasons), things would not work. That is why I
suggested that this fictiocious mechanism needs to keep track of the changes
and keep the values synced.

However, for my current purposes the macro will be ok!
Cheers

2011/10/25 Robby Findler <robby at eecs.northwestern.edu>

> If you are willing to change the existing uses of parameterize, then you
> could use a macro to introduce a continuation mark along with the parameter
> setting. Would that work?
>
> Robby
>
>
> On Tuesday, October 25, 2011, Ismael Figueroa Palet <ifigueroap at gmail.com>
> wrote:
> > Robby,
> >
> > The solution you gave works with what I want to do. Thanks!
> >
> > The only issue is that the rest of the codebase is already assuming that
> the values are stored using parameterize, so I need to change all those
> points to use with-continuation-mark in addition to parameterize.
> >
> > Is there any way to configure parameterize so it also introduces a
> continuation mark with the same name, and make sure the values are always
> synced (and so it is captured when exceptions are raised)?
> >
> > It would be something like:
> >
> > (parameterize ([param value #:also-as-continuation-mark]) e)
> >
> > So if I do (current-continuation-mark 'param) it will return the adequate
> value, in addition to being accessible as a parameter.
> >
> > Thanks again!
> >
> > --
> > Ismael
> >
> > 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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