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Clarify add-to-list documentation (bug#39373)

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While add-to-list often works with lexical variables, this is a hack
that isn't always effective; better tell the user not to try.

* doc/lispref/lists.texi (List Variables): Add a note about lexical
variables to the add-to-list description.  Fix the equivalent code.
* lisp/subr.el (add-to-list): Amend doc string.
This commit is contained in:
Mattias Engdegård 2020-02-01 20:11:11 +01:00
parent d3d2ea927c
commit d07f177382
2 changed files with 7 additions and 2 deletions
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8
doc/lispref/lists.texi
View file

@ -777,6 +777,9 @@ non-@code{nil}, it is added at the end.
The argument @var{symbol} is not implicitly quoted; @code{add-to-list} The argument @var{symbol} is not implicitly quoted; @code{add-to-list}
is an ordinary function, like @code{set} and unlike @code{setq}. Quote is an ordinary function, like @code{set} and unlike @code{setq}. Quote
the argument yourself if that is what you want. the argument yourself if that is what you want.
Do not use this function when @var{symbol} refers to a lexical
variable.
@end defun @end defun
Here's a scenario showing how to use @code{add-to-list}: Here's a scenario showing how to use @code{add-to-list}:
@ -799,8 +802,9 @@ foo ;; @r{@code{foo} was changed.}
@var{value})} is this: @var{value})} is this:
@example @example
(or (member @var{value} @var{var}) (if (member @var{value} @var{var})
(setq @var{var} (cons @var{value} @var{var}))) @var{var}
(setq @var{var} (cons @var{value} @var{var})))
@end example @end example
@defun add-to-ordered-list symbol element &optional order @defun add-to-ordered-list symbol element &optional order

1
lisp/subr.el
View file

@ -1845,6 +1845,7 @@ COMPARE-FN if that's non-nil.
If ELEMENT is added, it is added at the beginning of the list, If ELEMENT is added, it is added at the beginning of the list,
unless the optional argument APPEND is non-nil, in which case unless the optional argument APPEND is non-nil, in which case
ELEMENT is added at the end. ELEMENT is added at the end.
LIST-VAR should not refer to a lexical variable.
The return value is the new value of LIST-VAR. The return value is the new value of LIST-VAR.