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Re: [Scheme-reports] must list-copy handle cycles?

On Tue, Jul 3, 2012 at 5:28 AM, Per Bothner <per@x> wrote:
> The text for list-copy seems to suggest that it must handle
> cyclic lists, but it doesn't explicitly say so.
> The Common Lisp Hyperspec says of copy-list:
>    The consequences are undefined if list is a circular list.
> If list-copy must handle cycles, what's a good algorithm?

Hair and tortoise works here - just use normal list-copy,
but if they ever meet up revert to the more expensive

For handling cycles in equal? you can refer to Clinger's
srfi-85 or:



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