On Apr 4, 2015, at 5:26 PM, Erik Silkensen <eriksilken...@gmail.com> wrote:
> Could someone explain how this example works?
>
> $ racket
> Welcome to Racket v6.1.1.
> -> (require racket/sandbox)
> -> (define racket-eval (make-evaluator 'racket))
> -> (define a (racket-eval '(set 1 2 3)))
> -> a
> (set 1 2 3)
> -> (set? a)
> #f
> -> (define racket-eval-again (make-evaluator 'racket))
> -> (equal? a (racket-eval-again '(set 1 2 3)))
> #f
>
> Is it something particular to set? (Or objects like that?)
I don’t really know how this works, but if you do this:
> (define racket-eval2
(parameterize ([sandbox-namespace-specs
(append (sandbox-namespace-specs)
`(racket/set))])
(make-evaluator 'racket)))
> (define b (racket-eval2 '(set 1 2 3)))
> (set? b)
#t
Then it works more like you would expect.
The documentation for sandbox-namespace-specs says this:
The module paths are needed for sharing module instantiations between the
sandbox and the caller. For example, sandbox code that returns posn values
(from the lang/posn module) will not be recognized as such by your own code by
default, since the sandbox will have its own instance of lang/posn and thus its
own struct type for posns. To be able to use such values, include 'lang/posn in
the list of module paths.
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