[ clisp-Bugs-3417358 ] 22.1.3.5 conformance

[SourceForge.net <no...@so...>]

Bugs item #3417358, was opened at 2011-10-03 01:45
Message generated for change (Comment added) made by haible
You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=101355&aid=3417358&group_id=1355

Please note that this message will contain a full copy of the comment thread,
including the initial issue submission, for this request,
not just the latest update.
Category: clisp
Group: ANSI compliance issue
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Pascal J. Bourguignon (informatimago)
Assigned to: Bruno Haible (haible)
Summary: 22.1.3.5 conformance

Initial Comment:
As per 22.1.3.5, 

    (write (quote (john (quote s) weight)) :pretty nil :readably nil)

should print

    (JOHN (QUOTE S) WEIGHT)

but instead it prints:

    (JOHN 'S WEIGHT)


[and similarly for :readtably t, it prints:
     
   (|COMMON-LISP-USER|::|JOHN| '|COMMON-LISP-USER|::|S| |COMMON-LISP-USER|::|WEIGHT|)
instead of:

   (|COMMON-LISP-USER|::|JOHN| (|CL|:|QUOTE| |COMMON-LISP-USER|::|S|) |COMMON-LISP-USER|::|WEIGHT|)
]

========================================================================
Implementation: CLISP 2.49 (2010-07-07) (built 3499302370) (memory 3499302538) on X86_64

Reading of: "(write (quote (john (quote s) weight)) :pretty nil :readably nil)"
signaled no error

Evaluation of: (WRITE '(JOHN 'S WEIGHT) :PRETTY NIL :READABLY NIL)
signaled no error
wrote nothing on *ERROR-OUTPUT*
wrote the following *STANDARD-OUTPUT* (lines excluded):
------------------------------------------------------------------------
(JOHN 'S WEIGHT)
------------------------------------------------------------------------
returned the following value:
--> (JOHN 'S WEIGHT)

========================================================================



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

>Comment By: Bruno Haible (haible)
Date: 2011-10-03 10:07

Message:
Your interpretation of CLHS 22.1.3.5 is debatable.
CLHS never explicitly says under which conditions it is OK to print (QUOTE
FOO) as 'FOO. Likewise for backquote, for which clisp
has an elaborate algorithm.
Therefore IMO it's an omission.

CLHS 22.1.3.5 says "list notation is preferred over dot notation". It does
not say "list notation is preferred over quote and backquote notation".

The description of *print-readably* says that the "standard readtable" can
be assumed when reading objects. Therefore you can
assume that the read-macro for #\' is in place, as much as you can assume
that the read-macros for #\( and #\) are in place.

The rationale for clisp's behaviour is that the symbol QUOTE, when it
occurs in lists, most often occurs when printing a piece of a
program. In this case, printing 'FOO instead of (QUOTE FOO) is always a
win in legibility. Changing clisp to print (QUOTE FOO)
when *print-pretty* is false -- like SBCL does -- would be a regression,
IMO.


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

You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=101355&aid=3417358&group_id=1355