Re: result of completing-read contradicting require-match

[Jean Louis <bugs@gnu.support>]

* Yuri Khan <yuri.v.khan@gmail.com> [2022-07-02 22:56]:
> On Sun, 3 Jul 2022 at 02:29, Jean Louis <bugs@gnu.support> wrote:
> 
> > REQUIRE-MATCH can take the following values:
> > - a function, which will be called with the input as the parameter.
> >   If it returns a non-nil value, the minibuffer is exited with that value.
> 
> > other way to persist asking until you get the true result is here:
> >
> > (defun rcd-repeat-until-not-empty-string (function &rest args)
> >   "Repeat FUNCTION with optional ARGS until result is not empty string."
> >   (let ((result))
> >     (while (string-empty-p (setq result (apply function args))))
> >       result))
> 
> Based on the quoted part of the docstring, you could probably pass a
> function that returns t for an allowed value, and nil for disallowed
> values, including an empty string or nil.

I would like to do that Yuri. I was thinking about it, and it bothers
me. I would like to merge these two functions and use each of them
sometimes singly. The third merged one would check for both values.

(defun rcd-repeat-until-not-nil (function &rest args)
  "Repeat FUNCTION with optional ARGS until result is not nil."
  (let ((result))
    (while (not (setq result (apply function args))))
    result))

(defun rcd-repeat-until-not-empty-string (function &rest args)
  "Repeat FUNCTION with optional ARGS until result is not empty string."
  (let ((result))
    (while (string-empty-p (setq result (apply function args))))
      result))

You say to pass the function to check for allowed values. Do you mean
then to have something like 

(defun rcd-repeat- (function check-function &args) ?

Example usage would be like:

(rdc-repeat-until-something 'read-from-minibuffer)

but also

(rdc-repeat-until-something 'read-number)

and here is what I come up with, 

(defun rcd-is-something-p (thing)
  "Return TRUE if THING is something."
  (cond ((and (stringp thing) (seq-empty-p thing)) nil)
	((and (numberp thing) (not thing)) nil)
	(t t)))

(defun rcd-repeat-until-something (function &rest args)
  "Repeat FUNCTION with optional ARGS until result is something.

Result shall be non empty string or number."
  (let ((result))
    (while (rcd-is-nothing-p (setq result (apply function args))))
      result))

Then I can tell for example:

rcd-repeat-until-something 'read-from-minibuffer "Say: ") ⇒ "Something"

without being allowed to exit the loop until the result is there.

But then I am also checking for number to be non-nil as well.

-- 
Jean

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