[plt-scheme] When does eqv? differ from eq? , from equal?

I almost always perform tests with eq? or equal?, seldom (if ever)  
with eqv? . The Reference is a bit mysterious, saying (in section 3.1)

Two values are eqv? if and only if they are eq?, unless otherwise  
specified for a particular datatype.

That doesn't help much. Well, it does help, but only by telling me  
that they are usually the same. Heuristically, I think of eq? as  
being similar to comparing pointers in C and equal? as a test that  
might involve library call that could run in time proportional to the  
size of the objects (e.g., strcmp). What is the intuition behind eqv?

"In the human mind, one-sidedness has
always been the rule and many-sidedness the
  exception. Hence, even in revolutions of
thought, one part of the truth usually sets while
  another rises."
--John Stuart Mill

http://www.gwoodhouse.com
http://GregWoodhouse.ImageKind.com





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