Re: Elisp - Function returning a list

[Jean Louis]

* Yuri Khan <yuri.v.khan@gmail.com> [2020-12-16 07:39]:
> On Wed, 16 Dec 2020 at 11:30, <steve-humphreys@gmx.com> wrote:
> >
> > For me 800 is 8 O'Clock
> 
> You cannot just do decimal arithmetics on times written in that format.
> 
> Start: 800  End: 1100  Skip: 45
> Expected: 800 845 930 1015 1100
> Actual: 800 845 890 935 980 1025 1070

I am using external tools that have features built-in, PostgreSQL
database has it.

(defun my-time-range (time-start add-hours interval-in-minutes)
  (interactive "MBegin time by format HH:MM: \nMFor how many hours later? 
\nMInterval in minutes: ")
  (let* ((sql (format "SELECT to_char(t.hour::timestamp,'HH:MI') FROM 
generate_series('2020-01-01 %s:00'::timestamp, '2020-01-01 %s:00'::timestamp + 
interval '%s hours',  '%s minutes'::interval) as t(hour);" time-start 
time-start add-hours interval-in-minutes))
         (command (format "psql -tc \"%s\"" sql)))
    (insert (shell-command-to-string command))))

With: 10:00 and 20 hours later with interval of 35 minutes, result is:

 10:00
 10:35
 11:10
 11:45
 12:20
 12:55
 01:30
 02:05
 02:40
 03:15
 03:50
 04:25
 05:00
 05:35
 06:10
 06:45
 07:20
 07:55
 08:30
 09:05
 09:40
 10:15
 10:50
 11:25
 12:00
 12:35
 01:10
 01:45
 02:20
 02:55
 03:30
 04:05
 04:40
 05:15
 05:50

To make a list from external command, then:

(defun my-time-range (time-start add-hours interval-in-minutes)
  (interactive "MBegin time by format HH:MM: \nMFor how many hours later? 
\nMInterval in minutes: ")
  (let* ((sql (format "SELECT to_char(t.hour::timestamp,'HH:MI') FROM 
generate_series('2020-01-01 %s:00'::timestamp, '2020-01-01 %s:00'::timestamp + 
interval '%s hours',  '%s minutes'::interval) as t(hour);" time-start 
time-start add-hours interval-in-minutes))
         (command (format "psql -qtc \"%s\"" sql))
         (result (shell-command-to-string command))
         (list (split-string result "\n"))
         (list (mapcar #'string-trim list))
         (list (delete-if #'seq-empty-p list)))
    list))

(my-time-range "10:00" "20" "35") => ("10:00" "10:35" "11:10" "11:45" "12:20" 
"12:55" "01:30" "02:05" "02:40" "03:15" "03:50" "04:25" "05:00" "05:35" "06:10" 
"06:45" "07:20" "07:55" "08:30" "09:05" "09:40" "10:15" "10:50" "11:25" "12:00" 
"12:35" "01:10" "01:45" "02:20" "02:55" "03:30" "04:05" "04:40" "05:15" "05:50")

Maybe such Emacs package does exist but if little fiddling with
the external tool helps me to get the range, then I use external
tool.

Jean