does this routine exist? until (while until true)

Asked Jul 09 '19 at 08:03

Active Jul 09 '19 at 08:03

Viewed 55 times

I found myself needing this control loop and was very surprised not to find it in the standard library. Does it exist by some other name?

(defmacro until (form &optional guard)
  "Runs `while' on FORM until it is non-nil, returning the value.

A guard is provided which may cause the loop to exit early with nil."
  (let ((res (gensym "res")))
    `(let (,res)
       (while (and (not ,guard)
                   (not (setq ,res ,form))))
       ,res)))

asked Jul 09 '19 at 08:03

fommil

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It does in the form of a keyword in `cl-loop` macro, if that helps. – wvxvw Jul 09 '19 at 08:32
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Related emacs-devel thread: [Why is there no `until' in elisp?](https://lists.gnu.org/r/emacs-devel/2018-10/msg00239.html). – npostavs Jul 09 '19 at 09:46
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It exists, because you just wrote it. ;-) – Drew Jul 09 '19 at 14:42

does this routine exist? until (while until true)

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