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On 09/29/2011 05:25 PM, Andre van Tonder wrote:

> On a system that that invokes a compiler on the argument of EVAL, the compiler
> may depend on the textual representation of the code '(cons 1 2).  It may even
> do certain optimizations and rewritings based on the textual representation.
> Again, having procedure objects in here confuses levels and can cause problems
> for such a compiler.

Does it really? Can anyone point to an implementation of EVAL that can't
cope with this?

The counter-argument is that it's useful for implementing sandboxes with
controlled gaps in them. One can wrap an expression in a let that
shadows away dangerous operations (or the ability to re-import them),
but then binds some symbols to procedures from outside the sandbox
(closing over sandbox state) that allow controlled access to things;
then eval it in (scheme-report-environment 7).

ABS

- --
Alaric Snell-Pym
http://www.snell-pym.org.uk/alaric/
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