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Re: Any infrastructure to select one of a few options in Emacs core?

From: John Mastro
Subject: Re: Any infrastructure to select one of a few options in Emacs core?
Date: Thu, 19 May 2016 18:16:22 -0700

Marcin Borkowski <> wrote:
> I went with this code:
> --8<---------------cut here---------------start------------->8---
> (defun select-choice (message choices)
>   "Display a buffer with MESSAGE and then CHOICES.
> Each element of CHOICES should be a cons cell, whose car is the
> result and the cdr is the description.  The user may select one
> by pressing a digit."
>   ;; TODO: This function is way too simple and not fool-proof!
>   (if (> (length choices) 9)
>       (error "Too many choices!")
>     (save-window-excursion
>       (pop-to-buffer " *amsrefs doi selection*" t t)
>       (delete-other-windows)            ; TODO: this should be fixed
>       (erase-buffer)
>       (insert message "\n\n")
>       (let ((i 0))
>         (dolist (choice choices)
>           (setq i (1+ i))
>           (insert (format "%d. %s\n\n" i (cdr choice)))))
>       (let ((key (read-key)))
>         (if (<= 49 key 57)
>             (car (nth (- key 49) choices))
>           (error "Wrong key pressed!"))))))
> --8<---------------cut here---------------end--------------->8---
> As it is said in the comment, it is far from ideal, but the whole
> program I've been writing for my friend is one big quick hack, so
> I didn't bother too much.

I've sometimes wanted something like this too.

I played around with a few cosmetic changes to your function and ended
up with this:

(defun read-choice (prompt choices)
  (if (> (length choices) 9)
      (error "Too many choices (max 9)")
    (let ((cursor-in-echo-area t)
          (prompt (if (get-text-property 0 'face prompt)
                    (propertize prompt
        (pop-to-buffer " *Read choice*" t t)
        (setq-local cursor-type nil)
        (let ((i 0))
          (dolist (choice choices)
            (setq i (1+ i))
            (insert (propertize (number-to-string i)
                    (format " %s\n" (cdr choice))))
          (goto-char (point-min))
          (let ((key (- (read-key prompt) 48)))
            (if (<= 1 key i)
                (car (nth (1- key) choices))
              (user-error "Invalid key"))))))))

Same functionality but posted anyway in the spirit of sharing :)

Why did you find `delete-other-windows' necessary? (Your TODO mentions
that it should be "fixed", so I assume you would have preferred not to
use it.)


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