[ clisp-Bugs-3452284 ] #'get DEFAULT value for existent properties with a value nil

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Bugs item #3452284, was opened at 2011-12-06 03:17
Message generated for change (Tracker Item Submitted) made by jakwings
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Category: clisp
Group: build problems
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Jak Wings (jakwings)
Assigned to: Bruno Haible (haible)
Summary: #'get DEFAULT value for existent properties with a value nil

Initial Comment:
Sorry, my English is a little poor.

Linux name 2.6.38-13-generic #52-Ubuntu SMP Tue Nov 8 16:48:07 UTC 2011 i686 i686 i386 GNU/Linux

I build it just by "sudo apt-get install clisp"

~$ clisp --version
GNU CLISP 2.48 (2009-07-28) (built 3508041772) (memory 3527376723)
Software: GNU C 4.5.2 
i686-linux-gnu-gcc -g -O2 -W -Wswitch -Wcomment -Wpointer-arith -Wimplicit -Wreturn-type -Wmissing-declarations -Wno-sign-compare -Wno-format-nonliteral -O2 -fexpensive-optimizations -falign-functions=4 -DUNICODE -DDYNAMIC_FFI -DDYNAMIC_MODULES -I. -Wl,-Bsymbolic-functions  /usr/lib/libreadline.so -lncurses -ldl /usr/lib/libavcall.so /usr/lib/libcallback.so  -L/usr/lib -lsigsegv 
SAFETY=0 HEAPCODES LINUX_NOEXEC_HEAPCODES GENERATIONAL_GC SPVW_BLOCKS SPVW_MIXED TRIVIALMAP_MEMORY
libsigsegv 2.5
libreadline 5.2
Features: 
(ASDF2 ASDF CLC-OS-DEBIAN COMMON-LISP-CONTROLLER BERKELEY-DB
 CLX-ANSI-COMMON-LISP CLX READLINE REGEXP SYSCALLS I18N LOOP COMPILER CLOS MOP
 CLISP ANSI-CL COMMON-LISP LISP=CL INTERPRETER SOCKETS GENERIC-STREAMS
 LOGICAL-PATHNAMES SCREEN FFI GETTEXT UNICODE BASE-CHAR=CHARACTER PC386 UNIX)
C Modules: (clisp i18n syscalls regexp readline linux clx bdb)
Installation directory: /usr/lib/clisp-2.48/
User language: ENGLISH
Machine: I686 (I686) name [127.0.1.1]

PROBLEM:

[29]> (symbol-plist 'cat)
(ORGIN NIL SIZE SMALL SEX FEMALE)
[30]> (get 'cat 'origin 'unknown)
UNKNOWN
[31]> (get 'cat 'origin-ex 'unknown)
UNKNOWN
The book《Common Lisp: An Introduction to Symbolic Computation》says, "There is one way to distinguish a symbol having a property FOO with value
NIL from a symbol that does not have a FOO property at all."
SO, is this a implementation problem?
Thanks.

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