#!/usr/bin/perl -w
#
#Suit Split Calculator
#
#Calculates the probability of suit splits based on
#a given number of known cards outside the suit.
#
#Based on an algorithm provided by Marvin L. French
#(mlfrench@writeme.com)
#
#Send me email if you like it or have any bugs to
#report.
#
#Darin Takemoto
#takemoto@xtal0.harvard.edu
#takemoto@thecia.net
#
START: $known1 = &entry("known cards", "Hand 1");
	$known2 = &entry("known cards", "Hand 2");
	$testtotal = &entry("cards", "test suit");
	if (($known1 + $known2 + $testtotal) > 26) {
		printf "Too many cards.\n";
		goto START
	};

	$maxtest1 = $maxtest2 = $testtotal;

	if (($known1 + $testtotal) > 13) { $maxtest1 = 13 - $known1 };
	if (($known2 + $testtotal) > 13) { $maxtest2 = 13 - $known2 };

	$num = &fact(13 - $known1) * &fact(13 - $known2) * &fact($testtotal) * &fact(26 - $known1 - $known2 - $testtotal);
	for ($i = $maxtest1; $i ge ($testtotal - $maxtest2); $i--) {
		$j = $testtotal - $i;
		$dem = &fact($i) * &fact($j) * &fact(13 - $known1 - $i) * &fact(13 - $known2 - $j) * &fact(26 - $known1 - $known2);
		$prob = $num/$dem;
		$prob = (int(($prob * 1000) + 0.5))/1000;	#round to 3 sig figs
		if ($prob == 0) {$prob = "< 0.0005"};	#even 0 means there is a small chance
		printf "Probability of $i cards in Hand 1 and $j cards in Hand 2: $prob\n";
	}
AGAIN: printf "Try again? (yn): ";
	$again = <STDIN>;
	chop($again);
	if ($again !~ /^(n|y)/i) {
		printf "Very funny.\n";
		goto AGAIN
	};
	if ($again =~ /^y/i) { goto START };
	printf "Bye bye!\n";
	exit 0;

#Subroutine to handle data entry
#
sub entry
{
$known = shift;
$name = shift;
SSUB:	printf "Enter number of $known in $name: ";
		$data = <STDIN>;
		chop($data);

		if ($data !~ /^\d+$/) {
			printf "Integers only, please.\n";
			goto SSUB
		};
		if (($data < 0) || ($data > 13)) {
			printf "Invalid number of cards in $name.\n";
			goto SSUB
		};
		return $data;
}

#Factorial function
#
sub fact
{
	$val = shift;
	if ($val < 0) { die "Invalid value for factorial:" };
	if ($val < 2) { return 1 };
	$temp = 1;
	for ($k = $val; $k > 1; $k--) {
		$temp *= $k;
	}
	return $temp;
}