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━━━━━━━━━━━━━━━
CHALLENGE 100
Andinus
━━━━━━━━━━━━━━━
2021-02-20
Table of Contents
─────────────────
Task 1 - Fun Time
.. Raku
Task 1 - Fun Time
═════════════════
You are given a time (12 hour / 24 hour).
Write a script to convert the given time from 12 hour format to 24
hour format and vice versa.
Ideally we expect a one-liner.
Raku
────
• Program: <file:raku/ch-1.raku>
One should use `DateTime' module to solve this but that is not fun so
we solve it the wrong way!
The program will accept any string as `$time'. We do the format check
later.
┌────
│ #| convert 12-hour formatted time to 24-hour format and vice-versa
│ unit sub MAIN (
│ Str $time, #= time (format: 05:15pm or "05:15 pm" or 17:00)
│ );
└────
The grammar `Time' will parse `$time' to give us meaningful
information required to do the task.
⁃ `hour' & `minute' match any digit ranging from 00 to 99
⁃ `meridiem' matches either /am/ or /pm/
⁃ Note: This grammar will consider "99:99" as a valid timestamp.
┌────
│ grammar Time {
│ token TOP { <hour> ':' <minute> ' '? <meridiem>? }
│ token hour { \d ** 1..2 }
│ token minute { \d ** 1..2 }
│ token meridiem { ['am'|'pm'] }
│ }
└────
We parse `$time' with `Time' grammar. If `meridiem' is set then it
must be 12-hour format time, otherwise it'll be 24-hour format time.
┌────
│ # Match for time format.
│ if Time.parse($time) -> $m {
│ given $m<meridiem> {
│ ...
│ }
│ } else {
│ note "Wrong format!";
│ exit 1;
│ }
└────
For "am" we just check if the hour is 12, if so then we print it as
"00" otherwise just print the hour.
┌────
│ when 'am' {
│ printf "%02d:%02d\n",
│ $m<hour> == 12 ?? "00" !! $m<hour>,
│ $m<minute>;
│ }
└────
If the hour is < 12 then we print `hour + 12' otherwise just print the
hour.
┌────
│ when 'pm' {
│ printf "%02d:%02d\n",
│ $m<hour> < 12 ?? $m<hour> + 12 !! $m<hour>,
│ $m<minute>;
│ }
└────
If the hour is 0 then print 12 otherwise check if it's > 12, if so
then print `hour - 12' otherwise just print the hour.
23 -> 11
greater than 12
00 -> 12
equal to 0
12 -> 12
neither equal to 0, nor greater than 12
If the hour is < 12 then print "am" otherwise print "pm".
┌────
│ default {
│ printf "%02d:%02d%s\n",
│ $m<hour> == 0 ?? "12" !! $m<hour> > 12 ?? $m<hour> - 12 !! $m<hour>,
│ $m<minute>, $m<hour> < 12 ?? "am" !! "pm";
│ }
└────
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