1. The CLHS page for SLOT-VALUE calls it a "function" as opposed to an
"accessor" although you can do (setf (slot-value ... )) .Is this an
oversight ? Because with every other function I can think of which can
be used with SETF , the corresponding CLHS page calls it an "accessor".

2. The same page says

If an attempt is made to read a slot and no slot of the name slot-name
exists in the object, slot-missing is called as follows:
[...]

If an attempt is made to write a slot and no slot of the name slot-name
exists in the object, slot-missing is called as follows:
[...]

The specific behavior depends on object's metaclass. An error is never
signaled if object has metaclass standard-class. An error is always
signaled if object has metaclass built-in-class.

What specific behaviour depends ? Is it what will happen if SLOT-MISSING gets
called ? The page for SLOT-MISSING doesn't say anything about dependency on
an object's metaclass.

--
vlaho.ninja/prog

Spiros Bousbouras <spibou@gmail.com> wrote:
> 1. The CLHS page for SLOT-VALUE calls it a "function" as opposed to an
> "accessor" although you can do (setf (slot-value ... )) .Is this an
> oversight ? Because with every other function I can think of which can
> be used with SETF , the corresponding CLHS page calls it an "accessor".

Doesn't matter, but perhaps an oversight.

> The specific behavior depends on object's metaclass. An error is never
> signaled if object has metaclass standard-class. An error is always
> signaled if object has metaclass built-in-class.
>
> What specific behaviour depends ? Is it what will happen if SLOT-MISSING gets
> called ? The page for SLOT-MISSING doesn't say anything about dependency on
> an object's metaclass.

Whether SLOT-VALUE signals error or calls SLOT-MISSING or SLOT-UNBOUND in
the appropriate cases: it never signals an error and always calls
SLOT-MISSING or SLOT-UNBOUND for objects whose metaclass is STANDARD-CLASS,
it always signals an error for objects of metaclass BUILT-IN-CLASS, and for
objects of other metaclasses its behaviour is undefined, which allows it to
work, or not work, for structures & conditions (am not sure metaclass of
conditions is specified, structures is).

--
the small snake

On Wed, 16 Mar 2022 09:20:12 -0000 (UTC)
Zyni Moë <no_email@invalid.invalid> wrote:
> Spiros Bousbouras <spibou@gmail.com> wrote:

[...]

> > The specific behavior depends on object's metaclass. An error is never
> > signaled if object has metaclass standard-class. An error is always
> > signaled if object has metaclass built-in-class.
> >
> > What specific behaviour depends ? Is it what will happen if SLOT-MISSING gets
> > called ? The page for SLOT-MISSING doesn't say anything about dependency on
> > an object's metaclass.
>
>
> Whether SLOT-VALUE signals error or calls SLOT-MISSING or SLOT-UNBOUND in
> the appropriate cases: it never signals an error and always calls
> SLOT-MISSING or SLOT-UNBOUND for objects whose metaclass is STANDARD-CLASS,
> it always signals an error for objects of metaclass BUILT-IN-CLASS, and for
> objects of other metaclasses its behaviour is undefined,

Actually unspecified.

> which allows it to
> work, or not work, for structures & conditions (am not sure metaclass of
> conditions is specified, structures is).

Ok , I had a look on the CLHS page for BUILT-IN-CLASS and it's clear now.
Initially I had read the "Whether SLOT-VALUE signals ..." text as referring
to the situation where one attempts to read or write a slot and "no slot of
the name slot-name exists in the object" .But the page for BUILT-IN-CLASS
makes it clear that

Calling slot-value on an instance of a built-in class signals an error of
type error.

I think the text on the SLOT-VALUE page would be clearer as follows :

Calling SLOT-VALUE on an instance of an object whose metaclass is
BUILT-IN-CLASS signals an error of type error.

For objects whose metaclass is STANDARD-CLASS:

If an attempt is made to read a slot and no slot of the name
slot-name exists in the object, slot-missing is called as follows:

[...]

If an attempt is made to write a slot and no slot of the name
slot-name exists in the object, slot-missing is called as follows:

[...]

Calling SLOT-VALUE on an instance of an object whose metaclass is neither
BUILT-IN-CLASS nor STANDARD-CLASS has unspecified consequences.

--
vlaho.ninja/prog