Hi!
Just now playing a little with ABCL(1.3.2), I saw some strange behaviour:
CL-USER> '(2 . 5)
(2 . 5)
CL-USER> '(2 . 5 . 5)
(2 . 5)
CL-USER> (equal '(2 . 5) '(2 . 5 . 5))
T
while other implementations give me an error when i type '(2 . 5 . 5)
it's a bug or ANSI CL allows this?
Depends.
ANSI CL specifies the lisp reader in such a way that (2 . 5 . 5) is not a valid syntax.
However, ANSI CL specifies that implementation may extend the CL language, UNDER THE CONDITION that extensions BE DOCUMENTED.
Therefore, IF it is written in ABCL documentation that (2 . 5 . x) reads as (2 . 5)
THEN it is not a bug, but an ABCL specific extension,
ELSE it is a conformity bug, it should signal a READER-ERROR (or perhaps just an ERROR).
Notice that since this is an extensions on the reader macro character #\(, it could be expected that the standard reader macro character for #\( still exist in the system and be obtained by (copy-readtable NIL) which shall return the standard readtable.
For example, in ccl the default *readtable* is poluted by a lot of extensions such as the dispatching #/ #_ #$ macro characters, but you can throw them away with (setf *readtable* (copy-readtable NIL)). One could expect the same here.
--
__Pascal J. Bourguignon__