[racket-dev] Typed versions of untyped collections

From: Matthias Felleisen (matthias at ccs.neu.edu)
Date: Mon Dec 17 16:44:35 EST 2012

My understanding is that 

 -- Neil created a single file P, I believe it is typed 
 -- he tells you to load plot/typed/ for the typed version 
 -- he tells you to load plot/ for the untyped version 

Somewhere in this arrangement a call in some untyped client to a function f from P will cross a line. 

If this is wrong, I'd like to know where it goes wrong. 

---------------------------------------------

I like the submodule idea a lot. 







On Dec 17, 2012, at 4:16 PM, Robby Findler wrote:

> I don't understand Matthias's performance comments. If, in TR (require plot) actually gives me a typed version of the library and in R (require plot) gives me the untyped version of the library, then I am avoiding the performance the untyped/typed performance overhead properly. If, on the other hand, if I have to commit that (require plot) gives me either the untyped or the typed version, then I have to suffer the performance overhead when I require it from the "wrong" context.
> 
> Neil's original complaint also has validity, I think: if he provides a plot/typed today, and then later ports plot so it is typed, then he has to keep this extra thing around for what appears to not be a very good reason.
> 
> And while I do understand Sam's reluctance to mess with module resolution, I think that just not solving this problem is worse.
> 
> And finally (and perhaps this is the root of the problem), I cannot understand what TR actually does by reading its documentation.
> 
> For example, the docs for 'require' do not explain why I can make a copy of "list.rkt" (in the racket collection), call the copy "listt.rkt" and have that copy not work, but the original one does. Clearly TR is not just "get[ting] *exactly* the same file as in R", so I think Sam's comments are off base.
> 
> Robby
> 
> On Mon, Dec 17, 2012 at 2:51 PM, Sam Tobin-Hochstadt <samth at ccs.neu.edu> wrote:
> >
> > On Mon, Dec 17, 2012 at 3:27 PM, Robby Findler
> > <robby at eecs.northwestern.edu> wrote:
> > > I've long thought something along these lines is a good idea, but perhaps
> > > what I think is a good idea isn't what Matthias and Sam think is the bad
> > > idea.
> > >
> > > I think that it makes sense for 'require' in typed-racket to look in a
> > > different place than 'require' in untyped racket looks so that one can write
> > > the same require spec (in both the docs and the code) and have two versions
> > > of the same library, one that is typed and one that isn't typed. Then, then
> > > library writer, if they choose, can decide who pays what for going (or not)
> > > across the boundary between typed and untyped. (Or maybe submodules would be
> > > better.)
> >
> > I think this is exactly what Eli was suggesting, and what I think is a bad idea.
> >
> > > I think this is already happening in TR anyways, when I write
> > >
> > >   (require racket/list)
> > >
> > > I don't get the same file being loaded when that is in a TR program as when
> > > it is in a R program.
> >
> > You get *exactly* the same file as in R.  I think that (a) this is a
> > valuable invariant and (b) the mechanisms for violating this invariant
> > are all very worrying.
> >
> > Sam
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