RE: [External] : Use of an associated list with completing-read

[Heime <heimeborgia@protonmail.com>]

On Friday, April 19th, 2024 at 2:14 PM, Drew Adams <drew.adams@oracle.com> wrote:

> > Haw can I have an interactive function that
> > displays a list of elements from an associated
> > list using completing-read ?
> 
> 
> The elements of an alist are conses. Assuming
> that you really meant that you want to see and
> choose among the elements, then use this:
> 
> (completing-read
> "Choose an alist element: "
> (mapcar #'prin1-to-string my-alist)
> nil
> t)
> 
> That "displays" elements that match your
> input. Is that what you meant by "displays
> a list of elements"?
> 
> It returns a string such as "(a . 42)" for
> the alist element (a . 42). Then you can
> use (read "(a . 42)") to get a new cons
> that's `equal' to the cons in your alist. ___ 

> But if you don't really want to see the elements of the alist as completions, 
> but instead you want to see their keys, then just do this: 

> (completing-read "Choose an alist key: " my-alist nil t) 

Yes, I wanted to see the keys as completing entries.  Right, looking 
at the documentation COLLECTION can be an alist and will print the keys.

I had the cons cells the other way round, with the actual key as the cdr,
making completing-read display the wrong entry.

> If the alist keys are symbols then apply` intern' to the chosen string, to get
> the symbol key. Then use this to get the element with that key (the exact
> same cons, i.e., `eq', not just` equal):
> 
> (car (assq THE-SYMBOL my-alist)
> 
> I had to do a lot of guessing as to what
> you're really requesting. As usual, you
> don't make clear what you're after. And
> you don't show any code that you've tried
> so far.