[debbugs-tracker] bug#10146: closed (error in aput in assoc.el, Emacs 24, 23, and 22 (at least))

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Your message dated Mon, 05 Dec 2011 17:26:56 -0500
with message-id <address@hidden>
and subject line Re: bug#10146: error in aput in assoc.el, Emacs 24, 23, and 22 
(at least)
has caused the debbugs.gnu.org bug report #10146,
regarding error in aput in assoc.el, Emacs 24, 23, and 22 (at least)
to be marked as done.

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10146: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=10146
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> --- Begin Message ---
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>
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> Subject: 
>
> error in aput in assoc.el, Emacs 24, 23, and 22 (at least)
>
>
>
>
> Date: 
>
> Sun, 27 Nov 2011 00:53:59 -0500
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>
>
>
> The function aput in assoc.el  (within lisp/emacs-lisp) has two errors.
>
> 1. In the third case of the cond (see original below), when the alist is not
>     null, the key is already in the list (and thus at the head), and the value is not null,
>
>     the return value is incorrect.
>
>     The original returns the result of the setcar -- that is, the new entry -- rather than 
>     the modified alist as it should.
>
> 2. The documentation string indicates that nil is returned when the list is nil,
>
>     but this is incorrect. The modified list is returned, which will include the
>     new key-value pair.
>
> I have included below, in order: 1) the original function for reference, 2) a simple 
> case showing the problem, and 3) a fixed version of the function. Only two
>
> minor changes are required.
>
> (FWIW, I'm running on Mac OS X 10.5, Emacs 24 and 23 nextstep
> and Emacs 22 carbon.)
>
>
> ;; Original version (from the current emacs24 trunk)
>
> (defun aput (alist-symbol key &optional value)
>
>   "Inserts a key-value pair into an alist.
> The alist is referenced by ALIST-SYMBOL.  The key-value pair is made
> from KEY and optionally, VALUE.  Returns the altered alist or nil if
> ALIST is nil.
>
> If the key-value pair referenced by KEY can be found in the alist, and
>
> VALUE is supplied non-nil, then the value of KEY will be set to VALUE.
> If VALUE is not supplied, or is nil, the key-value pair will not be
> modified, but will be moved to the head of the alist.  If the key-value
> pair cannot be found in the alist, it will be inserted into the head
> of the alist (with value nil if VALUE is nil or not supplied)."
>   (lexical-let ((elem (aelement key value))
>         alist)
>     (asort alist-symbol key)
>     (setq alist (symbol-value alist-symbol))
>     (cond ((null alist) (set alist-symbol elem))
>
>       ((anot-head-p alist key) (set alist-symbol (nconc elem alist)))
>       (value (setcar alist (car elem)))
>       (t alist))))
>
> ;; Simple case illustrating the problem
> (require 'assoc)
> (progn
>   (setq tmp-alist '((a . 1)
>
>                     (b . 2)
>                     (c . 3)
>                     (d . 4)))
>   (setq tmp-ret1
>         (aput 'tmp-alist 'e 5))  ; no problem
>   (prin1 tmp-ret1)
>
>   (print "\n")
>
>   (setq tmp-ret2
>         (aput 'tmp-alist 'b 10))    ; oops
>   (prin1 tmp-ret2))
>
> ;; Fixed version of the function
> ;;
> ;; Changes:
> ;;   + The `values' case of the cond needs to return the
>
> ;;     alist *not* the value returned by setcar
> ;;   + The docstring indicating the return value has been
> ;;     corrected. The original was inaccurate about the
> ;;     case where the alist is nil.
> ;;
> ;; Note this needs (require 'cl) as in assoc.el for lexical-let
>
> (defun aput (alist-symbol key &optional value)
>   "Inserts a key-value pair into an alist.
> The alist is referenced by ALIST-SYMBOL.  The key-value pair is made
> from KEY and optionally, VALUE.  Returns the altered alist.
>
> If the key-value pair referenced by KEY can be found in the alist, and
> VALUE is supplied non-nil, then the value of KEY will be set to VALUE.
> If VALUE is not supplied, or is nil, the key-value pair will not be
>
> modified, but will be moved to the head of the alist.  If the key-value
> pair cannot be found in the alist, it will be inserted into the head
> of the alist (with value nil if VALUE is nil or not supplied)."
>   (lexical-let ((elem (aelement key value))
>
>         alist)
>     (asort alist-symbol key)
>     (setq alist (symbol-value alist-symbol))
>     (cond ((null alist)
>            (set alist-symbol elem))
>       ((anot-head-p alist key)
>            (set alist-symbol (nconc elem alist)))
>
>       (value
>            (setcar alist (car elem))
>            alist)
>       (t alist))))
>
>
> --- End Message ---
> --- Begin Message ---
>
>
>
> Subject: 
>
> Re: bug#10146: error in aput in assoc.el, Emacs 24, 23,	and 22 (at least)
>
>
>
>
> Date: 
>
> Mon, 05 Dec 2011 17:26:56 -0500
>
>
>
>
> User-agent: 
>
> Gnus/5.13 (Gnus v5.13) Emacs/24.0.91 (gnu/linux)
>
>
>
>
> > The function aput in assoc.el  (within lisp/emacs-lisp) has two errors.
>
> Thanks, installed.
> Note that assoc.el is very little used and I'd be happy to deprecate it,
> among other things because it does not use a "assoc-" prefix and is
> hence not clean w.r.t namespace.  So if you have good reasons to use it,
> I'd be happy to hear them,
>
>
>         Stefan
>
>
> --- End Message ---