Perl 6 - Starting with the basics - Fruitful subroutines(Ackermann function)

Think Perl 6

開発環境

• macOS Sierra - Apple (OS)
• Emacs (Text Editor)
• Perl 6 (プログラミング言語)
• Rakudo(コンパイラ、実装)

Think Perl 6: How to Think Like a Computer Scientist (Laurent Rosenfeld(著)、Allen B. Downey(著)、Oreilly & Associates Inc)のPart 1(Starting with the basics)、Chapter 5(Fruitful subroutines)の Exercise 5-2.を取り組んでみる。

Exercise 5-2.

コード(Emacs)

#!/usr/bin/env perl6
# -*- coding: utf-8 -*-

sub ack($m, $n) {
    return $n + 1 if $m == 0;
    return ack($m - 1, 1) if $m > 0 and $n == 0;
    return ack($m - 1, ack($m, $n - 1));
}

say ack(3, 4);
say ack(3, 4) == 125;

入出力結果(Terminal, REPL)

$ ./sample5_2.pl
125
True
$