Re: How to read an integer from the minibuffer

[Emanuel Berg via Users list for the GNU Emacs text editor <help-gnu-emacs@gnu.org>]

Yuri Khan wrote:

> I was going to suggest piggybacking on the JSON parser, but
> it has the same bug:
>
> M-: (json-read-from-string "123foo")
> ⇒ 123 (#o173, #x7b, ?\{)
>
> Fortunately, json-read-from-string is simple enough that you can copy
> and modify it:
>
> -(defun json-read-from-string (string)
> +(defun json-read-from-string-strict (string)
>    "Read the JSON object contained in STRING and return it."
>    (with-temp-buffer
>      (insert string)
>      (goto-char (point-min))
> -    (json-read)))
> +    (prog1 (json-read)
> +      (unless (eobp) (error "Trailing garbage")))))
>
> You still get some whitespace skipping though.

(defun string-to-number-number (str)
  (let ((s (string-trim str)))
    (if (string-match "^[+-]\\{0,1\\}\\(0+\\|0*\\.0+\\)$" s)
        0
      (let ((num (string-to-number s)))
        (when (and (not (zerop num))
                   (string-match "^[+-]\\{0,1\\}\\([[:digit:]]+\\|[[:digit:]]*\\.[[:digit:]]+\\)$" s) )
          num) ))))
;; (string-to-number-number " 10")                  ;  10
;; (string-to-number-number "  1.5")                ;   1.5
;; (string-to-number-number " +0")                  ;   0
;; (string-to-number-number "  0")                  ;   0
;; (string-to-number-number " -0.0")                ;   0
;; (string-to-number-number " -1.5")                ;   1.5
;; (string-to-number-number "-10")                  ; -10
;; (string-to-number-number "123this used to work") ; nil
;; (string-to-number-number "not a number")         ; nil

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