Hello,
(This is my first post. Please correct me if I missed anything. =) )
Currently, the built-in time parsing functions only allow us to parse timestrings with respect to some given formats (ISO-8601, RFC-822) [1]. I have a parsing function that allows users to parse with customized formats which are easy to write. The end result is:
``` emacs-lisp
(my/parse-time "20200718-201504"
'((:year 4) (:month 2) (:day 2) "-"
(:hour 2) (:minute 2) (:second 2)))
;; => ((:second . 4) (:minute . 15) (:hour . 20)
;; (:day . 18) (:month . 7) (:year . 2020))```
One can even parse org timestamps easily with the format
``` emacs-lisp
'("[" (:year 4) "-" (:month 2) "-" (:day 2) "]")
```
The code is ~25 lines long, which is easily extendable (see below). I wonder if there's any interest to add this into emacs. I can write tests and benchmarks to make sure that it doesn't change the user space.
``` emacs-lisp
;;; Actual code
(defun my/parse-time (str format)
"Parse time string with customized format, and return an alist.
A format is a list of directives. A directive is either a string
or a list (A B), where A is a keyword, and B is an integer."
(flet ((parse-step
(directive str)
(if (atom directive)
(if (string-match (format "^%s" directive) str)
(list (substring str (length directive)))
(error "Parsing failure~ directive: %s; str: %s." directive str))
(let* ((key (car directive))
(int (car (cdr directive)))
(to-parse (substring str 0 int))
;; TODO For natural lang, replace
;; parse-integer by any customized
;; transformers.
(value (cl-parse-integer to-parse)))
(list (substring str int) key value)))))
(let (result)
(while (not (equal str ""))
(let* ((return (parse-step (pop format) str))
(new-str (car return))
(key (car (cdr return)))
(value (car (cddr return))))
(setf str new-str)
(when key (setf (alist-get key result) value))))```