[Q] introspecting setf expanders

[Didier Verna]

Content preview: Hello, I cannot find a standard way to figure out whether
a setf expander has been defined for a symbol FOO (via either DEFSETF or
DEFINE-SETF-EXPANDER). Is there one? Otherwise, I would also be happy with
an SBCL-only solution. [...]

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Hello,

I cannot find a standard way to figure out whether a setf expander has
been defined for a symbol FOO (via either DEFSETF or
DEFINE-SETF-EXPANDER).

Is there one? Otherwise, I would also be happy with an SBCL-only
solution.


Thank you !

[Raymond Wiker]

Content preview: On Oct 8, 2012, at 15:28 , Didier Verna wrote: > Hello, >

I cannot find a standard way to figure out whether a setf expander has >

been defined for a symbol FOO (via either DEFSETF or > DEFINE-SETF-EXPANDER).

Is there one? Otherwise, I would also be happy with an SBCL-only > solution.

Thank you ! [...]

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Hello,
I cannot find a standard way to figure out whether a setf expander has
been defined for a symbol FOO (via either DEFSETF or
DEFINE-SETF-EXPANDER).
Is there one? Otherwise, I would also be happy with an SBCL-only
solution.
Thank you !

#'get-setf-expansion, perhaps?

[Didier Verna]

Content preview: Raymond Wiker <rwiker-***@public.gmane.org> wrote: > #'get-setf-expansion,
perhaps? Nope, because it gives you something by default. [...]

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Post by Raymond Wiker
#'get-setf-expansion, perhaps?

Nope, because it gives you something by default.

CL-USER> (get-setf-expansion '(not-previously-defined))
NIL
NIL
(#:NEW886)
(FUNCALL #'(SETF NOT-PREVIOUSLY-DEFINED) #:NEW886)
(NOT-PREVIOUSLY-DEFINED)

[Didier Verna]

Content preview: Pascal Costanza wrote: > Just guessing: If you see that the
writer form is a funcall to a setf > function, you can then check with fboundp
if such a function actually > exists. This is probably a bit shaky, but maybe
good enough for > practical purposes? [...]

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Archived-At: <http://permalink.gmane.org/gmane.lisp.cl-pro/725>

Just guessing: If you see that the writer form is a funcall to a setf
function, you can then check with fboundp if such a function actually
exists. This is probably a bit shaky, but maybe good enough for
practical purposes?

Good idea. To be more precise:

- if the writer form is something else than (FUNCALL #'(SETF FOO) ...)
then there is a defsetf going on (it even takes precedence over a
potential setf function).

- if the writer form is (FUNCALL #'(SETF FOO) ...) and that function is
bound, then there is a setf function going on but no defsetf.

- otherwise, there is no writer at all.


I think this might just work.

[Martin Simmons]

Pascal Costanza wrote: > > > Just guessing: If you see that the writer

form is a funcall to a setf > > function, you can then check with fboundp
if such a function actually > > exists. This is probably a bit shaky, but

- if the writer form is something else than (FUNCALL #'(SETF FOO) ...)

then there is a defsetf going on (it even takes precedence over a > potential

setf function). > > - if the writer form is (FUNCALL #'(SETF FOO) ...) and
that function is > bound, then there is a setf function going on but no defsetf.

- otherwise, there is no writer at all. > > > I think this might just

work. [...]

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Just guessing: If you see that the writer form is a funcall to a setf
function, you can then check with fboundp if such a function actually
exists. This is probably a bit shaky, but maybe good enough for
practical purposes?

- if the writer form is something else than (FUNCALL #'(SETF FOO) ...)
then there is a defsetf going on (it even takes precedence over a
potential setf function).
- if the writer form is (FUNCALL #'(SETF FOO) ...) and that function is
bound, then there is a setf function going on but no defsetf.
- otherwise, there is no writer at all.
I think this might just work.

As Pascal said, it's a bit shaky. E.g. a user could define

(defsetf foo (x) (y)
`(funcall #'(setf foo) ,y ,x))

which gives a false negative.

Also, it won't be portable, because the (FUNCALL #'(SETF FOO) ...) form isn't
required (the standard just specifies something with the same effect as it).

[Pascal Costanza]

Content preview: Just guessing: If you see that the writer form is a funcall
to a setf function, you can then check with fboundp if such a function actually
exists. This is probably a bit shaky, but maybe good enough for practical
purposes? [...]

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Archived-At: <http://permalink.gmane.org/gmane.lisp.cl-pro/726>

Just guessing: If you see that the writer form is a funcall to a setf function, you can then check with fboundp if such a function actually exists. This is probably a bit shaky, but maybe good enough for practical purposes?

Pascal

Post by Didier Verna

Post by Raymond Wiker
#'get-setf-expansion, perhaps?

Nope, because it gives you something by default.
CL-USER> (get-setf-expansion '(not-previously-defined))
NIL
NIL
(#:NEW886)
(FUNCALL #'(SETF NOT-PREVIOUSLY-DEFINED) #:NEW886)
(NOT-PREVIOUSLY-DEFINED)
--
Resistance is futile. You will be jazzimilated.
Scientific site: http://www.lrde.epita.fr/~didier
Music (Jazz) site: http://www.didierverna.com
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Pascal Costanza

[Pascal J. Bourguignon]

Content preview: IMO, you will have to see what's done by each implementation,
and use implementation specific, perhaps even internal functions to get that
information. This would be a good subject for a CDR, to provide a public
introspective API. [...]

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IMO, you will have to see what's done by each implementation, and use implementation specific, perhaps even internal functions to get that information.

This would be a good subject for a CDR, to provide a public introspective API.
--
__Pascal Bourguignon__

Post by Didier Verna
Hello,
I cannot find a standard way to figure out whether a setf expander has
been defined for a symbol FOO (via either DEFSETF or
DEFINE-SETF-EXPANDER).
Is there one? Otherwise, I would also be happy with an SBCL-only
solution.
Thank you !
--
Resistance is futile. You will be jazzimilated.
Scientific site: http://www.lrde.epita.fr/~didier
Music (Jazz) site: http://www.didierverna.com
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pro mailing list
http://lists.common-lisp.net/cgi-bin/mailman/listinfo/pro

[Marco Antoniotti]

Content preview: On Oct 9, 2012, at 07:52 , Pascal J. Bourguignon wrote: >
IMO, you will have to see what's done by each implementation, and use implementation
specific, perhaps even internal functions to get that information. > > This
would be a good subject for a CDR, to provide a public introspective API.
[...]

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Post by Pascal J. Bourguignon
IMO, you will have to see what's done by each implementation, and use implementation specific, perhaps even internal functions to get that information.
This would be a good subject for a CDR, to provide a public introspective API.

I second that. A "side" CDR would be to specify other "function specifiers" beside (SETF FOO).

Cheers
--
MA

Post by Pascal J. Bourguignon
--
__Pascal Bourguignon__

Post by Didier Verna
Hello,
I cannot find a standard way to figure out whether a setf expander has
been defined for a symbol FOO (via either DEFSETF or
DEFINE-SETF-EXPANDER).
Is there one? Otherwise, I would also be happy with an SBCL-only
solution.
Thank you !
--
Resistance is futile. You will be jazzimilated.
Scientific site: http://www.lrde.epita.fr/~didier
Music (Jazz) site: http://www.didierverna.com
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pro mailing list
http://lists.common-lisp.net/cgi-bin/mailman/listinfo/pro

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--
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DISCo, Università Milano Bicocca U14 2043 http://bimib.disco.unimib.it
Viale Sarca 336
I-20126 Milan (MI) ITALY

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