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#!/usr/bin/perl -s
use v5.16;
use Test2::V0;
use Memoize;
use experimental 'signatures';
no warnings 'recursion';
memoize('ackermann');
our ($tests, $examples);
run_tests() if $tests || $examples; # does not return
die <<EOS unless @ARGV == 2;
usage: $0 [-examples] [-tests] [M N]
-examples
run the examples from the challenge
-tests
run some tests
M N
calculate ackermann(M, N)
EOS
### Input and Output
say ackermann(@ARGV);
### Implementation
sub ackermann ($m, $n) {
return $n + 1 unless $m;
return ackermann($m - 1, 1) unless $n;
ackermann($m - 1, ackermann($m, $n - 1));
}
### Examples and tests
sub run_tests {
SKIP: {
skip "examples" unless $examples;
is ackermann(1, 2), 4;
is ackermann(2, 3), 9;
is ackermann(3, 4), 125;
is ackermann(4, 0), 13;
is ackermann(4, 1), 65533;
is ackermann(5, 0), 65533;
}
SKIP: {
skip "tests" unless $tests;
}
done_testing;
exit;
}
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