simple approach to ackermann

2 files changed, 36 insertions, 0 deletions

diff --git a/challenge-017/michael-hamlin/perl5/ch-1.pl b/challenge-017/michael-hamlin/perl5/ch-1.pl
new file mode 120000
index 0000000000..157cbc0453
--- /dev/null
+++ b/challenge-017/michael-hamlin/perl5/ch-1.pl
@@ -0,0 +1 @@
+t1-ackermann-simple.pl
\ No newline at end of file
diff --git a/challenge-017/michael-hamlin/perl5/t1-ackermann-simple.pl b/challenge-017/michael-hamlin/perl5/t1-ackermann-simple.pl
new file mode 100644
index 0000000000..02e03a644f
--- /dev/null
+++ b/challenge-017/michael-hamlin/perl5/t1-ackermann-simple.pl
@@ -0,0 +1,35 @@
+#! /usr/bin/env perl
+#
+
+use 5.22.0;
+use warnings;
+use feature 'signatures';
+no warnings 'experimental::signatures';
+use integer;
+
+# really need the big integers when $m >= 4
+# use bigint lib => 'GMP';
+
+no warnings 'recursion';
+
+my $count = 0;
+
+sub _ack( $m, $n ) {
+    $count++;
+    if ($m > 0) {
+        return _ack( $m - 1, 1 ) unless $n;
+        return _ack( $m - 1, _ack( $m, $n - 1));
+    } else {
+        return $n + 1;
+    }
+}
+sub ack ( $m, $n ) {
+    die "the function is not defined for negative parameters" if $m < 0 || $n < 0;
+    return _ack($m, $n);
+}
+
+die "must give two nonnegative integers as input" unless @ARGV > 1;
+
+$" = ', ';
+say "A( @ARGV ) = ", ack(@ARGV), "  ...after $count calls.";
+