[racket] lazy racket

The problem is that only applications are wrapped with the
toplevel-forcer. (And you don't actually need !!. Just the regular !
should be sufficient.)

For a short term solution, if you select Lazy Racket in the language
menu instead of #lang lazy, it will do what you want, due to a
subtlety in the way languages are implemented. Lazy Racket when
selected in the menu is implemented as a "tool", so top level
variables are wrapped with #%top, which gets forced. #lang languages
are module languages and module level variables have no such wrapping.

ps racket-dev, should the #%top from lazy racket be removed?




On Mon, Nov 14, 2011 at 2:53 PM, Eric Tanter <etanter at dcc.uchile.cl> wrote:
> Hi,
>
> I'd like to tweak Lazy Racket such that the top-level interactions in the REPL always use `!!' (recursive force), in order to mimic Haskell's behavior as close as possible.
>
> If someone can help me in the very brief term, I would really appreciate it (I plan to start teaching on laziness using Lazy Racket tomorrow).
>
> Thanks in advance!
>
> -- Éric
>
> PS: Eli told me of some parameter that controls this behavior. I think it is `toplevel-forcer', but a) I'm not sure, b) even if I hack it manually (edit lazy.rkt), it does not work:
>
> ;; parameter is properly set to `!!'
>> (toplevel-forcer)
> #<procedure:!!>
>
>> ones
> #<promise:ones>
>
>> (!! ones)
> #0='(1 . #0#)
>
> I'd like the following behavior:
>> ones
> #0='(1 . #0#)
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