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Re: generic-function special form
There hasn't been enough conversation about this for us to converge. In
particular, Moon hasn't replied about whether or not he agrees that
generic-function efunctuates the method-function bodies contained in it.
It seems to me that generic-function is like function. It causes part
of its body to be efunctuated. It could be implemented as a macro and
have the same effect, but I don't see why that is a good idea.
To make things simpler for people who may not have the old messages
filed, here are all the messages I have on this topic:
Date: Fri, 29 Apr 88 14:25 PDT
One of the comments we received was:
Date: Fri, 15 Apr 88 13:43 PDT
From: David N Gray <Gray@DSG.csc.ti.com>
It is not apparent why GENERIC-FUNCTION needs to be a special form
instead of a macro.
Because Common Lisp doesn't have lambda macros.
No, that's wrong, because GENERIC-FUNCTION is not something that can be
used inside the FUNCTION special form. In other words, GENERIC-FUNCTION
evaluates, it doesn't efunctuate. As far as I can see GENERIC-FUNCTION
could be a macro that expands into MAKE-INSTANCE <generic-function-class>
and a bunch of initargs including some that are forms that construct methods.
I think Gray is right on this one and it's a mistake in the document.
We should check with RPG, who proposed this.
I am surprised to here that generic-function cannot be used inside the
function special form. It doesn't say that in the documentation, and
since the method bodies are supplied as forms, I think this must
efunctuate. It must capture the lexical scope it was used in or else
what is it worth?
Date: 30 Apr 88 10:19 PDT
From: Dick Gabriel <RPG@SAIL.Stanford.EDU>
On GENERIC-FUNCTION special form:
It's true I proposed it to be a special form. I did that so it
would be parallel to FUNCTION. I had even imagined some #<mumble>
reader macro for it. Unlike FUNCTION, GENERIC-FUNCTION can be a macro
for MAKE-INSTANCE. In Qlisp we have a macro called QLAMBDA which is
like LAMBDA except it cannot be used inside FUNCTION etc. It turns out
to be a drag because the differences between how you can use QLAMBDA
and how you can use LAMBDA seem gratuitous. Similarly, I thought that
folks would prefer to see GENERIC-FUNCTION be as similar to FUNCTION as
GENERIC-FUNCTION as a macro can efunctuate what it needs to inside the
#'lambda's that appear inside the method-forming part of the expansion of
the macro. I can imagine people making mistakes the first time they write
Date: Mon, 2 May 88 08:58:20 CDT
From: Patrick H Dussud <DUSSUD@Jenner.csc.ti.com>
I think that a macro will work. A macro can return a form that capture
the lexical environment if it contains lambda forms.
Date: Mon, 02 May 88 08:54:39 -0700
Arguments on the side of making it a special form are those cited by RPG
and Gregor, namely that consistency between the way function and
generic-function work seems like a good idea (RPG's qlambda example) and
the need for capturing the lexical environment (Gregor). On the minus
side is the stated goal of Common Lisp to limit the number of special
forms and the obvious macroexpansion for generic-function.
I tend to think that generic-function should be a special form, for
the arguments cited, and because it seems like a different enough
piece of functionality to justify going beyond the goal of limiting