🚀 go-pugleaf

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 ))