[racket-dev] 5.0.2 changelog

About a minute ago, Sam Tobin-Hochstadt wrote:
> On Thu, Oct 28, 2010 at 12:41 PM, Eli Barzilay <eli at barzilay.org> wrote:
> > About a minute ago, Sam Tobin-Hochstadt wrote:
> >> On Thu, Oct 28, 2010 at 12:29 PM, Eli Barzilay <eli at barzilay.org> wrote:
> >> > Three hours ago, Matthias Felleisen wrote:
> >> >>
> >> >> On Oct 28, 2010, at 8:34 AM, Matthew Flatt wrote:
> >> >> >
> >> >> > None seem especially worth mentioning, but the internal-definition
> >> >> > change could be mentioned if we need more to Say:
> >> >> >
> >> >> > * The `when', `unless', `cond', `case', and `match' forms (in
> >> >> >   `racket/base' and derived languages) now allow immediate
> >> >> >   internal definitions.
> >> >>
> >> >> Just for the record: allowing internal definitions all over the
> >> >> place and mixing them properly with expressions has been one of the
> >> >> best small changes of the decade.
> >> >
> >> > BTW, there's another one that I think should get the same: `begin0'.
> >>
> >> That would be weird.  What do these do?
> >>
> >> (begin0 (define x 1) x)
> >> (let ([x 0]) (begin0 x (define x 1))
> >
> > I don't see what should be weird, those would be similar syntax errors
> > to what you get from
> >
> >  (begin0 (define x 1) (let () x))
> 
> This isn't any different from my first example.  What did you mean here?

I mean that the suggested `begin0' that I'm talking about will be
implemented with a `(let () ...)' around the body, and therefore the
error that you would get with

  (begin0 (define x 1) x)

is the same that you get now with:

  (begin0 (define x 1) (let () x))


> >  (let ([x 0]) (begin0 x (let () (define x 1))))
> 
> What about
> 
> (let ([x 0]) (begin0 x (define-syntax x #'1)))
> 
> or
> 
> (let ([x 0]) (begin0 x (define-syntax x #'1) 7))
> ?

Same for all of these (first is a syntax error, second is 0).  I don't
see anything problematic or surprising.

-- 
          ((lambda (x) (x x)) (lambda (x) (x x)))          Eli Barzilay:
                    http://barzilay.org/                   Maze is Life!