[racket-dev] Things we could move out of the core

At Fri, 28 Jun 2013 17:43:42 -0400, Sam Tobin-Hochstadt wrote:
> On Fri, Jun 28, 2013 at 5:17 PM, Matthew Flatt <mflatt at cs.utah.edu> wrote:
> > At Fri, 28 Jun 2013 17:08:19 -0400, Sam Tobin-Hochstadt wrote:
> >> On Fri, Jun 28, 2013 at 5:02 PM, Matthew Flatt <mflatt at cs.utah.edu> wrote:
> >> > At Fri, 28 Jun 2013 14:38:03 -0400, Sam Tobin-Hochstadt wrote:
> >> >> On Thu, Jun 27, 2013 at 8:45 PM, Robby Findler
> >> >> <robby at eecs.northwestern.edu> wrote:
> >> >> > Did you consider moving "#lang mzscheme" out as well?
> >> >>
> >> >> I've now created another pull request that does this, here:
> >> >> https://github.com/plt/racket/pull/377
> >> >>
> >> >> There's one remaining question.  The `make-base-namespace` procedure
> >> >> provided by `mzscheme` attaches the `mzscheme` module.  But this pull
> >> >> request removes that module, so it can't be attached or required in
> >> >> this code.  The alternatives are:
> >> >>
> >> >> 1. Just attach/require `scheme/mzscheme`.  Slightly incompatible in
> >> >> some corner cases.
> >> >> 2. Don't remove `mzscheme` from the core.
> >> >> 3. Remove `make*-namespace` from `scheme/mzscheme` and implement them
> >> >> in the `mzscheme` collection in the `mzscheme` package.
> >> >>
> >> >> I'm currently leaning toward 3 but I'd appreciate anyone else's thoughts.
> >> >
> >> > Is there some reason that `scheme/mzscheme' can't move to the
> >> > "mzscheme" package (along with `racket/private/stxmz-body')?
> >>
> >> Because large portions of the core are written in the `mzscheme`
> >> language (or `scheme/mzscheme`, after my patch), some of which feature
> >> evaluating code in mzscheme-like namespaces.  If we can somehow get
> >> around the latter problem, then the former is a Small Matter of
> >> Programming, but it'll take a little while.
> >
> > Ah --- I had not actually looked at 9587a2f.
> >
> > I guess I'm confused on the goal, since I don't see changing `mzscheme'
> > to `scheme/mzscheme' as a step forward. Can you say more about the
> > intent of changing `mzscheme' to `scheme/mzscheme'?
> 
> The intent is to reduce the API surface area provided by the core.
> Note that `scheme/mzscheme` is not a documented API.  Thus, moving the
> `mzscheme` language and collection would require anyone who depended
> on them to explicitly depend on another package. At some later point,
> we finish implementing the core without using `scheme/mzscheme`, move
> the actual implementation of `mzscheme` to the `mzscheme` package,
> without any compatibility problems.

I see what you mean, but it feels wrong to me that `scheme/mzscheme'
exists and isn't documented. I'd prefer to work toward getting it in
the right package and documented.

> > Meanwhile, I worry that options 1 and 3 can create subtle and confusing
> > bugs/incompatibilities. (I've spent a lot of time on problems that
> > happened due to accidentally choosing similar options in the past.)
> 
> (1) definitely has the potential for subtle bugs. I believe that (3)
> is semantics preserving *except* insofar as some part of the core was
> using the `mzscheme` namespace creation functions, and would thus work
> differently. However, there are only two places in the core that use
> `make-namespace` from `mzscheme`.  They are (a) the `setup/unpack`
> code using `eval` that you plan to remove and (b) a part of
> `compiler/private/xform.rkt` for loading precompiled headers. I don't
> know what the latter does, or if changing it to use a Racket namespace
> would have the potential to introduce bugs.
> 
> But yes, there's definitely a worry about subtle bugs here.

There's also the issue that `scheme/mzscheme' introduces an
`for-syntax' import of `scheme/mzscheme', and not a `for-syntax' import
of `mzscheme', so `make-base-namespace' would disappear from phase 1 in
`mzscheme' --- if I'm following correctly.

So, I think option 2 is right for now, and we should eventually spend
cycles on really getting `mzscheme' out of the core.