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structure equality in slisp
From: David.Butcher at ML.RI.CMU.EDU
To: Gripe at ML.RI.CMU.EDU
Re: structure equality in slisp
(equal (make-point) (make-point)) returned nil.
a point is just three slots containing a number each.
according to the book, things that have the same print name are equal.
so shouldn't equal work on structures?
Unfortunately, EQUAL is not a structural equality predicate. For
historical reasons, EQUAL on any atom other than a string (or a
bit-vector) is equivalent to EQL. Even worse, *there is no structural
equality predicate* in Common Lisp. You can use EQUALP, but then
comparisons of characters are case-insensitive. Yes, this is
misleading, confusing and inconsistent. I think it sucks. Flame