Re: Replacement for `aput' from obsolete assoc.el?

[Michael Heerdegen <michael_heerdegen@web.de>]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

> Usually, for alists, you can do:
>
>  (push (cons key val) alist)
>
> If you want to do it via side-effects, then it largely depends on what
> kind of "alist" this is.  If you know the key is already in there, you
> can do
>
>   (setcdr (assoc key alist) val)

So I think I want something like that:

(defun my-aput (alist-sym key val)
  (let ((cons (assoc key (symbol-value alist-sym))))
    (if cons (setcdr cons val) (push (cons key val) (symbol-value alist-sym)))))

  
> >> instead of `eq')?  Dunno why this function does not exist yet, but it
> >> would ease handling alists e.g. if its keys are strings.
>
> Using side-effects on alists is often a bad idea.

Why?  I do this very often in my .emacs.  For example:


--8<---------------cut here---------------start------------->8---
(aput 'find-constituents 'readable (list 0))

(eval-after-load "linkd"
  '(aput 'minor-mode-alist 'linkd-mode '(" Ld")))

(aput 'default-frame-alist 'width 104)

(aput 'warning-suppress-types 'undo '(discard-info))

(aput 'auto-mode-alist "\\.v?dired\\'" 'dired-virtual-mode)

(aput 'org-show-siblings 'org-goto t)

(aput 'w3m-search-engine-alist
          "duckduckgo" '("http://duckduckgo.com/?q=%s"))
--8<---------------cut here---------------end--------------->8---


Is it a bad idea in these cases?


> - Code bundled with Emacs-24.2 is still not "allowed" to use the CL
>   function you showed (i.e. `delete*').  It can require the new `cl-lib'
>   and use `cl-delete' instead, tho.

Will it be ok to require cl-lib at run-time in third-party packages?
That would be great.


Thanks,

Michael.