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Jim Blandy <jimb@red-bean.com> writes: > > 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. You're of course right---silly me. /mdj