[ clisp-Bugs-1482533 ] print-object built-in object: no-applicable-method

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Bugs item #1482533, was opened at 2006-05-05 10:34
Message generated for change (Comment added) made by sds
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Category: clisp
Group: ANSI compliance issue
>Status: Closed
>Resolution: Fixed
Priority: 5
Submitted By: Jörg Höhle (hoehle)
>Assigned to: Sam Steingold (sds)
Summary: print-object built-in object: no-applicable-method

Initial Comment:
CLHS says about PRINT-OBJECT: "Each implementation is 
required to provide a method on the class standard-
object and on the class
structure-object. In addition, each implementation 
must provide methods on enough other classes so as to
ensure that there is always an applicable method."

Contrary to this, print-object signals a NO-APPLICABLE-
METHOD:
(print-object 2 *standard-output*)
*** - NO-APPLICABLE-METHOD: When calling
       #<STANDARD-GENERIC-FUNCTION PRINT-OBJECT>
      with arguments (2 #<IO SYNONYM-STREAM *TERMINAL-
IO*>), no method is
      applicable.

I came across this trying out the CLHS example about 
pprint dispatch tables:
(set-pprint-dispatch '(cons (member my-let)) 
                      (pprint-dispatch '(let) nil))
With NO-APPLICABLE-METHOD, the following identity 
mentioned abour PPRINT-DISPATCH does not hold:
(let ((*print-pretty* t))
  (write object :stream s))
==  (funcall (pprint-dispatch object) s object)
because pprint-dispatch defers to PRINT-OBJECT which 
errors out.

Regards,
 Jörg Höhle

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Comment By: Sam Steingold (sds)
Date: 2006-07-27 15:59

Message:
Logged In: YES 
user_id=5735

thank you for your bug report.
the bug has been fixed in the CVS tree.
you can either wait for the next release (recommended)
or check out the current CVS tree (see http://clisp.cons.org)
and build CLISP from the sources (be advised that between
releases the CVS tree is very unstable and may not even build
on your platform).

----------------------------------------------------------------------

Comment By: Sam Steingold (sds)
Date: 2006-07-27 11:30

Message:
Logged In: YES 
user_id=5735

instead of tediously writing a defmethod for each and every
built-in class, I would rather have something like

(defconstant print-object-methods-<instance-of-built-in-class>
  (list (defmethod print-object (obj (out stream)) (write
obj :stream out))))
(remove-method #'print-object
               (first
print-object-methods-<instance-of-built-in-class>))
(defmethod compute-applicable-methods-using-classes
    ((gf (eql #'print-object)) args)
  (multiple-value-bind (l p) (call-next-method)
    (if (and (null l)
             (eq (class-of (first args)) <built-in-class>)
             (eq (second args) <stream>))
        (values
print-object-methods-<instance-of-built-in-class> t)
        (values l p))))

alas, this causes a stack overflow in bootstrap
and has no effect when type at the prompt.

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