Path: utzoo!attcan!uunet!talos!kjones
From: kjones@talos.uu.net (Kyle Jones)
Newsgroups: comp.emacs
Subject: Re: Need read-number function
Message-ID: <1990Feb8.132524.1694@talos.uu.net>
Date: 8 Feb 90 13:25:24 GMT
References: <4300068@m.cs.uiuc.edu>
Reply-To: kyle@xanth.cs.odu.edu
Lines: 24

reingold@m.cs.uiuc.edu writes:
 > I need a function read-number that would behave like (interactive "n");
 > that is, it would keep trying until a numeric value was typed.

[ Assuming GNU emacs here... ]

Yah, I had to code this one myself.  I don't know if a function like
this should be standard in the distribution or not.  Common Lisp's
elephantiasis is largely due to adopting functions from everyone's
toolbox.

Anyway, here's the function.

(defun read-number (prompt &optional initial-input)
  "Read a number from the minibuffer prompting with PROMPT.
If non-nil, the optional second argument INITIAL-INPUT should be a string
to insert into the minibuffer before reading."
  (let (result)
    (while (null result)
      (setq result (read-string prompt initial-input))
      (if (string-match "^ *-?[0-9]+" result)
	  (setq result (string-to-int result))
	(setq result nil)))
    result ))