Path: utzoo!attcan!uunet!mcvax!inria!crin!stephan
From: stephan@crin.crin.fr (Stephan BRUNESSAUX)
Newsgroups: comp.lang.lisp
Subject: Re: Common Lisp Problems with Hash-table in Macros
Message-ID: <701@crin.crin.fr>
Date: 13 Dec 88 19:15:43 GMT
Reply-To: stephan@crin.crin.fr (Stephan BRUNESSAUX)
Organization: C.R.I.N
Lines: 57


In article <393@aipna.ed.ac.uk> you write:
>In article <698@crin.crin.fr> stephan@crin.crin.fr (Stephan BRUNESSAUX) writes:
>>Is there anybody out there who can explain me what is wrong with this
>>example which correctly runs in both interpreted and compiled mode on
>>Symbolics 3620 (Genera 7.2) and correctly ONLY in interpreted mode on
>>TI Explorer II and on VAX running KCL (June 3, 1987) but not in compiled
>>mode !?... 
>
>>    >(defmacro test (a b)  
>>       (let ((table (make-hash-table :size 1)))
>>         (setf (gethash a table) b)
>>         `(defun aux () 
>>            (maphash #'(lambda (key val) 
>>                         (format t "key: ~a - val: ~a~%" key val)) 
>>                     ',table))))
>
>The problem is that you're trying to compile some code that contains
>aquoted hash table.  So, the compiler has to put a representation of
>that hash table into the ".o" file.  In KCL, the hash table just gets
>PRINTed and so looks like this:
>
>   #<hash-table 0017a310>
>
>When LOAD tries to read this, it calls READ which sees the # and calls
>the reader for the # dispatching character macro.  It then sees the <
>and signals an error.
>
>I don't know what happens on the Explorer.


My first question is : why the compiler does not DUMP the hash table ?

The above example correctly runs if you supersede the hash table by a vector
(with some changes to display the contents).

On Symbolics, the hash table is DUMPed; so, you can read or modify the hash
table after loading the compiled file.
On KCL, it is impossible since it is a PRINTed representation which is
compiled.
On Explorer, the hash table seems to be dumped but no longer works since you
cannot add or remove any entries.

My second question is : Am I right to write that kind of macro ? 

My third question is : As far as I developped on Symbolics (in Common Lisp 
package) a big software using that kind of macros, is it normal to encounter
such problems on others Common Lisps ?

            Thanks for all suggestions.
                  STEPHAN.

-- 
Stephan Brunessaux
CRIN-INRIA Lorraine
BP 239 - 54506 VANDOEUVRE CEDEX - FRANCE
E-MAIL: stephan@crin.crin.fr