Perl 6 - Starting with the basics - Case Study: Word Play(Puzzler, regular expressions, string(substr, flip), for loop)

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 8(Case Study: Word Play)の Exercise 8-7、8-8、8-9.を取り組んでみる。

Exercise 8-7、8-8、8-9.

コード(Emacs)

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

say '7.';

my $filename = 'words.txt';

for $filename.IO.lines {
    say $_ if $_ ~~ /(.)$0(.)$1(.)$2/;
}

say '8.';

sub first_l(Str $word) {
    return substr $word, 0, 1;
}
sub last_l(Str $word) {
    return substr $word, *-1, 1;
}
sub middle_l(Str $word where $word.chars > 1) {
    return substr $word, 1, *-1;
}

sub is-palindrome(Str $word) {
    return True if $word.chars <= 1;
    return is-palindrome middle_l($word) if first_l($word) eq last_l($word);
    False;
}

for 100000..999999 {
    if (is-palindrome(~$_.substr(2, 4)) and
        is-palindrome(~($_ + 1).substr(1, 5)) and
        is-palindrome(~($_ + 2).substr(1, 4)) and
        is-palindrome(~($_ + 3))) {
        
        say $_;
    }
}

say '9,';

my $age1 = 20;
my $age2 = 50;
for $age1..$age2 -> $diff {
    my $count = 0;
    for 0..(100 - $diff) -> $i {
        my $mum = $i + $diff;
        if ~$i eq $mum.flip {
            say "ME: $i, MUM: $mum";
            $count++ 
        }        
    }
    say "$count: $diff" if $count > 0;
}

入出力結果(Terminal, REPL)

$ ./sample7.pl
7.
bookkeeper
bookkeepers
bookkeeping
bookkeepings
8.
198888
199999
9,
ME: 14, MUM: 41
ME: 25, MUM: 52
ME: 36, MUM: 63
ME: 47, MUM: 74
ME: 58, MUM: 85
ME: 69, MUM: 96
6: 27
ME: 15, MUM: 51
ME: 26, MUM: 62
ME: 37, MUM: 73
ME: 48, MUM: 84
ME: 59, MUM: 95
5: 36
ME: 16, MUM: 61
ME: 27, MUM: 72
ME: 38, MUM: 83
ME: 49, MUM: 94
4: 45
$