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Re: DEFSTRUCT and predicates
Date: Tue, 26 Nov 1985 18:27 EST
From: Skef Wholey <Wholey@C.CS.CMU.EDU>
Subject: DEFSTRUCT and predicates
In-Reply-To: Msg of 26 Nov 1985 17:20-EST from NGALL at BBNG.ARPA
Date: Tuesday, 26 November 1985 17:20-EST
From: NGALL at BBNG.ARPA
The only complexity in the CL "-P" heuristic is dealing with qualified
predicates such as string-(lessp). Since defstruct created predicates
will ALWAYS be suffixing data-type names (NEVER existing predicate
names), defstruct can safely use the simple hyphenation heuristic,
i.e., if the data-type name is hyphenated, add "-P", otherwise add
"P". Can anyone think of counter-examples?
(defstruct (space-person (:include person))
Space-Person-P (or Space-Personp) is what you call a "qualified predicate."
Hmmm. I think I disagree. I don't think Space-Person-P falls under
the CL definition of "qualified predicate":
1. The rationale for for NOT hyphenating the "P" in "STRING-LESSP" is
that it would "incorrectly imply that it is a predicate that tests for
a kind of object called a STRING-LESS." This is exactly what we WANT
to imply in the case of SPACE-PERSON; so the predicate should be
2. Your definition by example would require that SIMPLE-STRING-P
become SIMPLE-STRINGP, BIT-VECTOR-P become BIT-VECTORP, etc., since
STRINGP, VECTORP, etc., are already predicates.
3. In my opinion, the only predicates that retain their
"P"s "as is" are predicates such as lessp, greaterp, equalp, i.e.,
non-type-predicates. And these are the kind of predicate that
defstruct will never have to deal with.