[racket] Making namespaces meet

I should have clarified that I have a little exceptional environment (#%top
override), and the dynamic evals used to work in the default environment,
like you said. I can't change it back to default, though, so I need some
other solution. The examples in the manual don't seem to quite deal with
this kind of case.

I tried for example the following:
((lambda ()
   (define ns (make-base-namespace)) ; create a new namespace?
   (current-namespace ns) ; apply it to take effect before the next lines
define?
   (define x 5)
   (eval '(list 1 2) ns)      >> ( 1 2)
   x                          >> 5
   (eval '(list 1 2 x) ns)))  >>  reference to undefined identifier: x


I'll next look into racket/load, thanks.


br, jukka

> -----Original Message-----
> From: Ryan Culpepper [mailto:ryanc at ccs.neu.edu]
> Sent: 05 November 2010 18:04
> To: Jukka Tuominen
> Cc: users at racket-lang.org
> Subject: Re: [racket] Making namespaces meet
>
>
> On 11/05/2010 05:53 AM, Jukka Tuominen wrote:
> >
> > Hi,
> >
> > I'm having trouble of getting namespaces meet when making dynamic
> > definitions. I made a simple example below.
> >
> > ((lambda ()
> >     (define x 10)
> >     (eval (list 'define 'y 5))
> >     (+ x y)))
> >
> > ;>>  reference to undefined identifier: y
> >
> >
> >
> > I then tried to "store" one of the namespaces and pass it on to
> another, but
> > I guess that's not the way the namespaces work.
> >
> >
> >
> > ((lambda ()
> >     (define namespace (current-namespace))
> >     (define x 10)
> >     (eval (list 'define 'y 5) namespace)
> >     (+ x y)))
> >
> > ;>>  reference to undefined identifier: y
> >
> >
> > Any ideas how to solve this?
>
> Both of your examples work at the racket repl. They should also work at
> the DrRacket repl. They fail only when you put them inside of a module
> (eg, the DrRacket definitions window after #lang racket), because a
> module must have no free references when it is compiled, even if those
> references would be defined during the execution of the module.
>
> Read reflection chapter of the Guide for more information:
>
>    http://docs.racket-lang.org/guide/reflection.html
>
> The short answer is that to make DrRacket's definitions window act more
> like an ordinary repl, use the racket/load language. That is, change
> #lang racket to #lang racket/load. It seems you'll have to print out the
> results yourself, though; racket/load doesn't do it automatically.
>
> Ryan