87 lines
1.9 KiB
Perl
Executable File
87 lines
1.9 KiB
Perl
Executable File
#!./perl
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#
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# test recursive functions.
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#
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print "1..23\n";
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sub gcd ($$) {
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return gcd($_[0] - $_[1], $_[1]) if ($_[0] > $_[1]);
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return gcd($_[0], $_[1] - $_[0]) if ($_[0] < $_[1]);
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$_[0];
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}
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sub factorial ($) {
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$_[0] < 2 ? 1 : $_[0] * factorial($_[0] - 1);
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}
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sub fibonacci ($) {
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$_[0] < 2 ? 1 : fibonacci($_[0] - 2) + fibonacci($_[0] - 1);
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}
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# Highly recursive, highly aggressive.
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# Kids, don't try this at home.
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#
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# For example ackermann(4,1) will take quite a long time.
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# It will simply eat away your memory. Trust me.
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sub ackermann ($$) {
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return $_[1] + 1 if ($_[0] == 0);
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return ackermann($_[0] - 1, 1) if ($_[1] == 0);
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ackermann($_[0] - 1, ackermann($_[0], $_[1] - 1));
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}
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# Highly recursive, highly boring.
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sub takeuchi ($$$) {
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$_[1] < $_[0] ?
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takeuchi(takeuchi($_[0] - 1, $_[1], $_[2]),
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takeuchi($_[1] - 1, $_[2], $_[0]),
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takeuchi($_[2] - 1, $_[0], $_[1]))
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: $_[2];
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}
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print 'not ' unless (($d = gcd(1147, 1271)) == 31);
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print "ok 1\n";
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print "# gcd(1147, 1271) = $d\n";
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print 'not ' unless (($d = gcd(1908, 2016)) == 36);
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print "ok 2\n";
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print "# gcd(1908, 2016) = $d\n";
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print 'not ' unless (($f = factorial(10)) == 3628800);
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print "ok 3\n";
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print "# factorial(10) = $f\n";
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print 'not ' unless (($f = factorial(factorial(3))) == 720);
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print "ok 4\n";
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print "# factorial(factorial(3)) = $f\n";
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print 'not ' unless (($f = fibonacci(10)) == 89);
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print "ok 5\n";
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print "# fibonacci(10) = $f\n";
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print 'not ' unless (($f = fibonacci(fibonacci(7))) == 17711);
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print "ok 6\n";
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print "# fibonacci(fibonacci(7)) = $f\n";
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$i = 7;
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@ack = qw(1 2 3 4 2 3 4 5 3 5 7 9 5 13 29 61);
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for $x (0..3) {
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for $y (0..3) {
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$a = ackermann($x, $y);
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print 'not ' unless ($a == shift(@ack));
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print "ok ", $i++, "\n";
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print "# ackermann($x, $y) = $a\n";
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}
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}
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($x, $y, $z) = (18, 12, 6);
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print 'not ' unless (($t = takeuchi($x, $y, $z)) == $z + 1);
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print "ok ", $i++, "\n";
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print "# takeuchi($x, $y, $z) = $t\n";
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