Perl 6 ExamplesPairing off
Author: Nelo Onyiah
In Pairing Off, competitors will be given a series of five playing cards and asked to determine the number of pairs.
Event Scenario
This is one of the less-complicated events, both to explain and to perform. In this event we'll be working with a standard deck of playing cards. A standard deck consists of four suits: Hearts, Spades, Clubs, and Diamonds. Within each suit are the numbers two through ten, plus a Jack, a Queen, a King, and an Ace.
Given a random set of five cards, your task is to find out how many pairs are in that set. In other words, if your five cards are the 2 of hearts, the 4 of spades, the 4 of clubs, the queen of diamonds and the queen of spades, you have 2 pairs: 2 fours and 2 queens. As another example, you might have a 3 of clubs, a 3 of diamonds, a 3 of hearts, a 10 of spades and an ace of hearts. In that case you have 3 pairs: 3 of clubs and 3 of diamonds; 3 of diamonds and 3 of hearts; and 3 of clubs and 3 of hearts.
For this event you should assume you've been dealt the following five cards:
Seven of spades
Five of hearts
Seven of diamonds
Seven of clubs
King of clubs
Using this set of cards, your script should display the number of pairs. Keep in mind that we will look at the scripts as we test them. A script that simply displays the number 3 will receive a score of 0; you actually have to do the calculations based on these cards. Not only that, but it shouldn't matter what the cards are: if we substitute any other set of five cards your script should still return the correct number of pairs.
USAGE
$ perl6 event001-j1n3l0.pl <cards>
NOTE
<cards> should be one of 2 .. 10, J, Q, K, A (though I don't check).
Source code: event001-j1n3l0.pl
use v6;
my @default-cards = qw{7 5 7 7 K};
sub MAIN(@cards = @default-cards) {
my $pairs = 0;
repeat {
my $card = @cards.shift;
for @cards -> $other_card {
$pairs++ if $card eq $other_card;
}
} until @cards.elems == 0;
say 'Total: ' ~ $pairs;
}