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bug#62746: [PATCH] Updated Elispref-Manual: `nil' cannot be defuned
From: |
Stefan Monnier |
Subject: |
bug#62746: [PATCH] Updated Elispref-Manual: `nil' cannot be defuned |
Date: |
Mon, 10 Apr 2023 10:14:59 -0400 |
User-agent: |
Gnus/5.13 (Gnus v5.13) |
>> “The symbols nil and void are Lisp objects, and can be stored into a
>> function cell just as any other object can be (and they can be valid
>> functions if you define them in turn with defun).”
>>
>> Updated:
>>
>> “The symbols nil and void are Lisp objects, and can be stored into a
>> function cell just as any other object can be (and void can be a
>> valid function if you define it with defun).”
>
> Why do you think the original text needs to be corrected?
Indeed, `nil` is treated specially to mean "not defined" when we try to
call a function:
Lisp_Object
funcall_general (Lisp_Object fun, ptrdiff_t numargs, Lisp_Object *args)
{
Lisp_Object original_fun = fun;
retry:
if (SYMBOLP (fun) && !NILP (fun)
&& (fun = XSYMBOL (fun)->u.s.function, SYMBOLP (fun)))
fun = indirect_function (fun);
if (SUBRP (fun) && !SUBR_NATIVE_COMPILED_DYNP (fun))
return funcall_subr (XSUBR (fun), numargs, args);
else if (COMPILEDP (fun)
|| SUBR_NATIVE_COMPILED_DYNP (fun)
|| MODULE_FUNCTIONP (fun))
return funcall_lambda (fun, numargs, args);
else
{
if (NILP (fun))
xsignal1 (Qvoid_function, original_fun);
-- Stefan