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

Are continuation marks thread- and continuation- safe as parameters?

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
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