Perl 6 - Starting with the basics - Strings - Debugging(is-reverse Subroutine)

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 7(Strings)、Debugging の Exercise: is-reverse Subroutine.を取り組んでみる。

Exercise: is-reverse Subroutine.

コード(Emacs)

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

sub is-reverse(Str $word1, Str $word2) {
    return False if $word1.chars != $word2.chars;

    my $i = 0;
    my $j = $word2.chars - 1;

    while $j >= 0 {
        say '$i = ', $i, ' $j = ', $j;
        return False if substr($word1, $i, 1) ne substr($word2, $j, 1);

        $i++;
        $j--;
    }
    return True;
}

say is-reverse('', '');
say not is-reverse('', 'a');
say not is-reverse('a', '');
say is-reverse('a', 'a');
say not is-reverse('ab', 'a');
say is-reverse('ab', 'ba');
say is-reverse('abcde', 'edcba');

say not is-reverse('日本語', 'abc');
say is-reverse('日本語', '語本日');

入出力結果(Terminal, REPL)

$ ./sample_rev.pl
True
True
True
$i = 0 $j = 0
True
True
$i = 0 $j = 1
$i = 1 $j = 0
True
$i = 0 $j = 4
$i = 1 $j = 3
$i = 2 $j = 2
$i = 3 $j = 1
$i = 4 $j = 0
True
$i = 0 $j = 2
True
$i = 0 $j = 2
$i = 1 $j = 1
$i = 2 $j = 0
True
$