Re: Predicate for true lists

["Basil L. Contovounesios" <contovob@tcd.ie>]

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Eli Zaretskii <eliz@gnu.org> writes:

>> Cc: contovob@tcd.ie, emacs-devel@gnu.org
>> From: Paul Eggert <eggert@cs.ucla.edu>
>> Date: Sat, 7 Jul 2018 01:41:38 -0700
>> 
>> Eli Zaretskii wrote:
>> > the documentation still doesn't say that 'length' signals
>> > an error for anything that is not a sequence, which is what
>> > proper-list-p is relying on.
>> 
>> The proposed implementation of proper-list-p does not rely on such a signal, 
>
> That's not my reading of the implementation:
>
>    (and (listp object) (ignore-errors (length object)))
>                         ^^^^^^^^^^^^^

Sorry, I completely overlooked Paul's message[1] that you were replying
to.  I now understand what you meant by your reading of the
implementation.

Given that the two of you suggested both the need for the doc fix and
its wording, I think you should ignore my patch[2] and push the change
yourself.  Here is yet another updated patch, should you disagree:


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From 79c6e0e80ebdcd0066654d72514dd08891155a77 Mon Sep 17 00:00:00 2001
From: "Basil L. Contovounesios" <contovob@tcd.ie>
Date: Sat, 7 Jul 2018 19:33:08 +0300
Subject: [PATCH] Fix (length NON-SEQUENCE) documentation

Suggested by Eli Zaretskii <eliz@gnu.org> and
Paul Eggert <eggert@cs.ucla.edu> in the following threads:
https://lists.gnu.org/archive/html/emacs-devel/2018-07/msg00171.html
https://lists.gnu.org/archive/html/emacs-devel/2018-07/msg00177.html
https://lists.gnu.org/archive/html/emacs-devel/2018-07/msg00206.html

* doc/lispref/sequences.texi (Sequence Functions): Mention that
'length' signals a 'wrong-type-argument' also when given a
non-sequencep argument.
---
 doc/lispref/sequences.texi | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/doc/lispref/sequences.texi b/doc/lispref/sequences.texi
index 59faf2b4f1..188a345114 100644
--- a/doc/lispref/sequences.texi
+++ b/doc/lispref/sequences.texi
@@ -71,13 +71,15 @@ Sequence Functions
 @cindex list length
 @cindex vector length
 @cindex sequence length
+@cindex bool-vector length
 @cindex char-table length
 @anchor{Definition of length}
-This function returns the number of elements in @var{sequence}.  If
-@var{sequence} is a dotted list, a @code{wrong-type-argument} error is
-signaled; if it is a circular list, a @code{circular-list} error is
-signaled.  For a char-table, the value returned is always one more
-than the maximum Emacs character code.
+This function returns the number of elements in @var{sequence}.  The
+function signals the @code{wrong-type-argument} error if the argument
+is not a sequence or is a dotted list; it signals the
+@code{circular-list} error if the argument is a circular list.  For a
+char-table, the value returned is always one more than the maximum
+Emacs character code.
 
 @xref{Definition of safe-length}, for the related function @code{safe-length}.
 
-- 
2.18.0


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[1]: https://lists.gnu.org/archive/html/emacs-devel/2018-07/msg00177.html
[2]: https://lists.gnu.org/archive/html/emacs-devel/2018-07/msg00207.html

Thanks,

-- 
Basil