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

From: Alan Watson (alan at alan-watson.org)
Date: Tue Oct 7 08:29:00 EDT 2008

> And eqv?, the function that started this
> whole topic, is useless as near as I can tell, since it is defined to
> be eq? unless you know the values you're comparing are numbers or
> characters (or a handful of "empty" values) in which case you're
> better off using a type-specific comparison function.

Um, eqv? is the fundamental identity predicate for data structures in  
Scheme. That is, if two data structures are eqv?, they cannot be  
distinguished by any finite composition of standard Scheme procedures  
except eq?, which, as I have said, is cheating.

So, eqv? seems pretty useful to me. Or, like Shriram, do you also  
never use case? :-)


Alan Watson

Posted on the users mailing list.