Try to understand the ora-company-number function again.

[Hongyi Zhao]

I try to understand the  ora-company-number function [1] again:

(defun ora-company-number ()
"Forward to `company-complete-number'.

Unless the number is potentially part of the candidate.
In that case, insert the number."
(interactive)
(let* ((k (this-command-keys))
(re (concat "^" company-prefix k)))
(if (or (cl-find-if (lambda (s) (string-match re s))
company-candidates)
(> (string-to-number k)
(length company-candidates))
(looking-back "[0-9]+\\.[0-9]*" (line-beginning-position)))
(self-insert-command 1)
(company-complete-number
(if (equal k "0")
10
(string-to-number k))))))

I've figured out all the intention of the above code snippet except
the following line:

(looking-back "[0-9]+\\.[0-9]*" (line-beginning-position)

I can't understand why the regexp used here must be written in this
form. Any hints will be appreciated.

[1] 
https://github.com/abo-abo/oremacs/blob/0c5f3284acedc966948cbb930e779af5189fd54e/modes/ora-company.el#L22

Regards
-- 
Assoc. Prof. Hongyi Zhao <hongyi.zhao@gmail.com>
Theory and Simulation of Materials
Hebei Vocational University of Technology and Engineering
No. 473, Quannan West Street, Xindu District, Xingtai, Hebei province