[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
forward-sexp and quote
From: |
Pascal Bourguignon |
Subject: |
forward-sexp and quote |
Date: |
20 Jan 2003 02:52:32 +0100 |
User-agent: |
Gnus/5.09 (Gnus v5.9.0) Emacs/21.2 |
(forward-sexp 1) eats quotes and backquotes, but (forward-sexp -1) doesn't.
That is, when there are spaces after the quote.
Which is unfortunate because the reader doesn't mind these spaces
and reads correctly the quoted expression:
.' (a b c) --(forward-sexp 1)--> ' (a b c). --(forward-sexp -1)--> ' .(a b c)
;; dot showing the point.
(show ' ( a b c))
==> (a b c)
The bug can be traced to scan-sexp which is a built-in.
(show (version))
==> "GNU Emacs 21.2.1 (i686-pc-linux-gnu, X toolkit)
of 2002-10-26 on thalassa"
(progn
(find-file "*bug*")
(emacs-lisp-mode)
(erase-buffer)
(mapc (lambda (s)
(let (before after end read-before read-after)
(goto-char (point-max))
(insert "\n")
(setq before (point))
(insert s)
(setq end (point))
(goto-char before)
(setq read-before (read-from-string (buffer-substring (point) end)))
(forward-sexp 1)
(forward-sexp -1)
(setq after (point))
(setq read-after (read-from-string (buffer-substring (point) end)))
(goto-char (point-max))
(insert (format "\nread before: %S\n" read-before))
(insert (format "read after : %S\n" read-after))
(insert (format "before=%S\nafter =%S %s\n\n" before after
(if (= before after) "" "BUG!")))))
'("' (a b c)" "'(a b c)" "' abc" "'abc")))
' (a b c)
read before: ((quote (a b c)) . 9)
read after : ((a b c) . 7)
before=2
after =4 BUG!
'(a b c)
read before: ((quote (a b c)) . 8)
read after : ((quote (a b c)) . 8)
before=101
after =101
' abc
read before: ((quote abc) . 5)
read after : (abc . 3)
before=207
after =209 BUG!
'abc
read before: ((quote abc) . 4)
read after : ((quote abc) . 4)
before=298
after =298
--
__Pascal_Bourguignon__ http://www.informatimago.com/
----------------------------------------------------------------------
There is a fault in reality. Do not adjust your minds. -- Salman Rushdie