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Re: eval'ing a self-referential vector


> A vector is a valid expression even if it is cyclic.
> 
> It is well-specified how to handle it: a vector is self-evaluating.
> 
> So, I'd say that we have to be able to handle it.

Hmm, I'm not sure I agree.  I think you're taking the correspondence
between Scheme data and expressions farther than R5RS does.

The set of valid Scheme expressions is defined in terms of a
context-free grammar, without reference to the structures one can
construct.  The definition is strictly textual, just like that of most
other languages.

Since there is no string which corresponds to a cyclic structure, I'd
say cyclic structures can't be valid expressions.

(The Scheme laywers take out their briefcases!  The courtroom goes
silent!  Doug Evans falls asleep!) :)