Re: [Gcl-devel] Re: setf

[Camm Maguire]

Hi Paul!  Thanks as always!

"Paul F. Dietz" <address@hidden> writes:

> Camm Maguire wrote:
> 
> 
> I don't believe defsetf causes a (setf ...) function to be defined
> at all.  Instead, it causes a setf *expander* to be defined.  Macros
> like SETF would call GET-SETF-EXPANSION to get this expansion.
> 

So (setf foo x) never uses the (setf foo) function definition if any?
What's the point of this function name if not anyway?  What are the
forms that use this function?  I already see that ((setf foo) ...) is
illegal. (function (setf foo) ) should work, and therefore (fboundp
#'(setf foo)), etc.  (defun (setf foo) ...) is the only way to define
this function, right?  Anything else I need to know?

Take care,

> Example from SBCL:
> 
> * (defun foo (x) (car x))
> 
> FOO
> * (defsetf foo rplaca)
> 
> FOO
> * #'(setf foo)
> 
> debugger invoked on condition of type UNDEFINED-FUNCTION:
>    The function (SETF FOO) is undefined.
> 
> Within the debugger, you can type HELP for help. At any command prompt (within
> the debugger or not) you can type (SB-EXT:QUIT) to terminate the SBCL
> executable. The condition which caused the debugger to be entered is bound to
> *DEBUG-CONDITION*. You can suppress this message by clearing
> *DEBUG-BEGINNER-HELP-P*.
> 
> restarts (invokable by number or by possibly-abbreviated name):
>    0: [ABORT   ] Reduce debugger level (leaving debugger, returning to 
> toplevel).
>    1: [TOPLEVEL] Restart at toplevel READ/EVAL/PRINT loop.
> (FDEFINITION 1 (SETF FOO))[:EXTERNAL]
> 0] 0
> 
> * (macroexpand '(setf (foo x) y))
> 
> (RPLACA X Y)
> T
> *
> 
>       Paul
> 
> 
> 
> 
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> 
> 
> 

-- 
Camm Maguire                                            address@hidden
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