Solution to task 1

1 files changed, 79 insertions, 0 deletions

diff --git a/challenge-175/jo-37/perl/ch-1.pl b/challenge-175/jo-37/perl/ch-1.pl
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+++ b/challenge-175/jo-37/perl/ch-1.pl
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+#!/usr/bin/perl -s
+
+use v5.16;
+use Test2::V0;
+use DateTime::Duration;
+use DateTime::Format::Strptime;
+use experimental 'signatures';
+
+our ($tests, $examples);
+
+run_tests() if $tests || $examples;	# does not return
+
+die <<EOS unless @ARGV;
+usage: $0 [-examples] [-tests] [YEAR]
+
+-examples
+    run the examples from the challenge
+ 
+-tests
+    run some tests
+
+YEAR
+    Print the date of each month's last Sunday in the given year.
+
+EOS
+
+
+### Input and Output
+
+say for last_sundays(shift);
+
+
+### Implementation
+
+# <blockquote>
+# `perl -ne 'print if 8..13' ../../../challenge-132/dave-jacoby/perl/ch-1.pl`
+# </blockquote>
+
+use constant MONTH =>
+    DateTime::Duration->new(months => 1, end_of_month => 'preserve');
+
+# YYYY-MM-DD
+use constant YMD =>
+    DateTime::Format::Strptime->new(pattern => '%F');
+
+# Returns an array of DateTime objects.
+sub last_sundays ($year) {
+    # Get the end of January.
+    my $jan31 = DateTime->new(
+        year => $year, month => 1, day => 31, formatter => YMD);
+
+    # For each month of the year, get the end day and go back to
+    # the previous Sunday. (day_of_week for Sunday is 7)
+    map $_->subtract(days => $_->day_of_week % 7),
+        map $jan31 + $_ * MONTH, 0 .. 11;
+}
+
+
+### Examples and tests
+
+sub run_tests {
+    SKIP: {
+        skip "examples" unless $examples;
+
+        is [last_sundays(2022)],
+        [qw(2022-01-30 2022-02-27 2022-03-27 2022-04-24 2022-05-29
+            2022-06-26 2022-07-31 2022-08-28 2022-09-25 2022-10-30
+            2022-11-27 2022-12-25)], 'example';
+    }
+
+    SKIP: {
+        skip "tests" unless $tests;
+
+        is +(last_sundays(2004))[1]->day_of_month, 29, 'Sun Feb 29 2004';
+	}
+
+    done_testing;
+    exit;
+}