[racket] Inductive and coinductive reasoning? (was "shared and immutable structures")

On Wed, Feb 02, 2011 at 11:30:45AM -0500, Shriram Krishnamurthi wrote:
> Yes you do.  Far less useful at our level.  But shared + immutable
> gives you coinductive.  That's why the distinction helps.

I'm not familiar with these terms and had trouble follwiong that
thread.  Would someone explain or point me to appropriate reading?

Thanks,
Mike