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#
# Perl Weekly Challenge - 035
# Task #1 and #2
#
#
# Mark Senn, http://engineering.purdue.edu/~mark
# November 24, 2019
#
# From
# https://perlweeklychallenge.org/blog/perl-weekly-challenge-035#task-1
# Contributed by Paul Johnson
# Write a program to encode text into binary encoded morse code.
#
# Pay attention to any changes which might need to be made to the
# text to make it valid morse code.
#
# Morse code (see https://en.wikipedia.org/wiki/Morse_code)
# consists of dots, dashes and gaps. It can be encoded in binary
# in the following fashion:
# dot: 1
# dash: 111
# intra-character gap: 0
# character gap: 000
# word gap: 0000000
#
# An intra-character gap is inserted between the dots and dashes
# in a character.
#
# This program converts text (variable name $plaintext) into binary
# encoded Morse code (variable name $ciphertext).
#
# Run using Raku v6.d;
use v6.d;
# Read the input from the command line. If no input is given
# use the string "42 db".
my $plaintext = '42 db';
@*ARGS.elems and $plaintext = "{@*ARGS}";
# Based on information in
# https://en.wikipedia.org/wiki/File:International_Morse_Code.svg
# I put a space between all dots and/or dashes to improve readability.
# This program only supports lowercase letters and digits. Add more
# plaintext symbols here if you'd like.
my %plain2cipher =
a => '. -', b => '- . . .', c => '- . - .',
d => '- . .', e => '.', f => '. . - .',
g => '- - .', h => '. . . .', i => '. .',
j => '. - - -', k => '- . -', l => '. - . .',
m => '- -', n => '- .', o => '- - -',
p => '. - - .', q => '- - . -', r => '. - .',
s => '. . .', t => '-', u => '. . -',
v => '. . . -', w => '. - -', x => '- . . -',
y => '- . - -', z => '- - . .', 1 => '. - - - -',
2 => '. . - - -', 3 => '. . . - -', 4 => '. . . . -',
5 => '. . . . .', 6 => '- . . . .', 7 => '- - . . .',
8 => '- - - . .', 9 => '- - - - .', 0 => '- - - - -';
# Replace %plain2cipher values with corresponding binary values.
for %plain2cipher.values -> $_ is rw {
s:g/'.'/1/; # dot
s:g/'-'/111/; # dash
s:g/' '/0/; # intra-character gap
}
# Compute %cipher2plain from %plain2cipher.
my %cipher2plain = %plain2cipher.invert;
#
# Convert plaintext to ciphertext.
#
"plaintext: $plaintext".say;
# Replace character gap and word gap with out-of-band characters---if they
# were expanded to their binary values here they could interfere with
# with $plaintext data.
$_ = $plaintext;
my $cgoob = '!'; # character gap
my $wgoob = '@'; # word gap
s:g/(\S)<before \S>/$0$cgoob/; # character gap
s:g/' '/$wgoob/; # word gap
# Replace in-band characters in $_ with their binary equivalents.
my $ciphertext = '';
for .comb(/./) {
%plain2cipher{$_}:exists
?? ($ciphertext ~= %plain2cipher{$_})
!! ($ciphertext ~= $_);
}
# Replace the out-of-band characters with their binary equivalents
$ciphertext ~~ s:g/$cgoob/000/;
$ciphertext ~~ s:g/$wgoob/0000000/;
"ciphertext: $ciphertext".say;
#
# Convert ciphertext to plaintext.
#
$_ = $ciphertext;
$plaintext = '';
my @word = .split(/0000000/); # word gap
loop (my $i = 0; $i < @word.elems; $i++) {
$_ = @word[$i];
my @char = .split(/000/); # character gap
for (@char) {
$plaintext ~= %cipher2plain{$_};
}
($i < @word.elems - 1) and $plaintext ~= ' ';
}
"plaintext: $plaintext".say;
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