Challenge #1: Cyymmdd -> yyyy-mm-dd dates in Perl6

1 files changed, 40 insertions, 0 deletions

diff --git a/challenge-038/ryan-thompson/perl6/ch-1.p6 b/challenge-038/ryan-thompson/perl6/ch-1.p6
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+#!/usr/bin/env perl6
+
+# ch-1.p6 - Weird dates. Convert Cyymmdd -> yyyy-mm-dd
+#
+# Ryan Thompson <rjt@cpan.org>
+
+use v6;
+
+sub MAIN( Int $date ) {
+    $date ~~ /^
+        $<cent> = [ <[12]> ]                         # Century (1:1900,2:2000)
+        $<yy>   = [ \d \d  ]                         # Year    (2-digit)
+        $<mm>   = [ 0<[1..9]> | 1<[012]> ]           # Month   (01..12)
+        $<dd>   = [ 0<[1..9]> | <[12]>\d | 3<[01]> ] # Day     (01..31)
+    $/ or die "Usage: $*PROGRAM Cyymmdd";
+
+    my Int $yyyy = ($<cent> + 18 ~ $<yy>).Int;
+
+    die "$yyyy-$<mm> does not have $<dd> days"
+        if days-in($yyyy, $<mm>.Int) < $<dd>;
+
+    say "$yyyy-$<mm>-$<dd>";
+
+}
+
+# Return the number of days in the given month (with year specified so
+# we can check if it is a leap year)
+sub days-in( Int $y, Int $m ) {
+    my @days = (0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31);
+    @days[2]++ if leap-year($y);
+    @days[$m];
+}
+
+# Return true if year is a leap year
+sub leap-year( Int $y ) {
+    return 1 unless $y % 400;
+    return 0 unless $y % 100;
+    return 1 unless $y % 4;
+    return 0;
+}