Subject: Re: Can SUBTYPEP fail?
From: rpw3@rpw3.org (Rob Warnock)
Date: Tue, 25 Mar 2003 08:49:52 -0600
Newsgroups: comp.lang.lisp
Message-ID: <CeWcnWdxwbQN8R2jXTWc-g@speakeasy.net>
Juanjo <worm@arrakis.es> wrote:
+---------------
| 4) The ANSI specification says nothing about exceptional conditions in
| SUBTYPEP.
+---------------

Not quite -- it says:

	Exceptional Situations: None. 

To me, that suggests "never throws an exception". In particular, given
the definition of SUBTYPEP, I should think that this should be fairly
reliable:

	(defun valid-subtype-spec-p (x)
	  (multiple-value-bind (subtype-p valid-p)
	      (subtypep x t)
	    (and subtype-p valid-p)))


-Rob

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