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Re: Name That Class
- To: common-lisp-object-system@SAIL.STANFORD.EDU
- Subject: Re: Name That Class
- From: David A. Moon <Moon@STONY-BROOK.SCRC.Symbolics.COM>
- Date: Thu, 6 Aug 87 22:14 EDT
- In-reply-to: <870728-192157-1316@Xerox>
Date: 28 Jul 87 19:21 PDT
It seems to me that there are ways for class-named and setf of such to
work. I think only two of these are reasonable, but I will include the
third for completeness. Note that this same analysis applies to
generic-function-name and setf of symbol-function and
get-setf-generic-function. I will do class names first.
A class C 'is bound to' a given name Ni iff (class-named Ni) returns C.
In all this solutions, we document class-named and setf of class-named.
We say that class-named returns the class is bound to a particular name.
We say that setf of class-named can be used to set the binding of a
class to a name.
All agreed, except I think we decided a month ago to rename class-named to
symbol-class, to be more consistent with the rest of Common-Lisp.
Only document class-named and setf of class-named. Most
implementations will have some magic for printing out a class's name
when it has one.
Document class-named and setf of class-named. Also document
class-name, but say that the the class may or may not 'bound' to that
Document class-named and class-names and setf of class-named. Say
that setf of class-named can be used to bind a clas to a name. Say that
class-names returns the list of all names that a class is bound to.
It seems to me that solution 1 and solution 3 are the only reasonable
ones. My general dislike of names makes me prefer solution 1, but I
think that solution 3 actually provides users some important
That's interesting, because I prefer solution 2, for the simple reason
that everything else I can think of that has a name works that way. The
symbol->object mapping is the "real" one, and the object->symbol mapping
is only a helpful hint for printing things out, but isn't necessarily kept
consistent with the symbol->object (a programming environment might try
to keep it consistent).
As far as I am concerned, any of these three would work. My objection
to solution 3 is primarily that it is more complicated. My objection to
solution 1 is that it is the same as solution 2 as soon as the users
discover what the name of the class-name function is, and no useful
purpose is served by making this name implementation-dependent.
(setf (class-named 'n1) nil)
#<Standard-Class N2 1>
Is this really how we want to undo these bindings? Nothing else in Common
Lisp I can think of works this way (storing nil). Also, a minor nit, CL
requires that such a setf form return nil, not the former value.
I think its easy to see how this whole thing would work for
generic-function-name, symbol-function, setf of symbol-function,
get-setf-generic-function and setf of get-setf-generic-function.
Agreed. Note that (setf (symbol-function 'foo) nil) isn't how we do
(fmakunbound 'foo) in CL currently.