Re: [Scheme-reports] Current tickets for the 5th ballot - 281

[Andre van Tonder <andre@x>]

On Thu, 29 Sep 2011, John Cowan wrote:

> Andy Wingo scripsit:
>
>>> #281 Make non-readable objects self-quoting in EVAL
>
> You can reproduce this with
>
> (define e (interaction-environment))
> (define x (list 'cons 1 2))
> (set-car! x cons)
> (define y (list (list 'quote 'cons) 1 2))
> (set-car! (cdar y) cons)
> (eval x e)
> (eval y e)

I don't think this ticket makes any sense.  Neither x nor y should be required 
to be evaluable.  It clashes with modules.  It confuses levels.  It may cause 
problems for systems that invoke a compiler on the argument of EVAL.

If e is a module environment (of which the interaction env. is a special case),
we need to look up the bindings of identifiers, including 'CONS, in the 
environment e, to determine the meaning of '(cons 1 2).  The environment is a 
mapping from identifiers to their meanings.  It is not defined on procedure 
objects.

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.

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