Merge pull request #345 from threadless-screw/threadless-screw-wk15ch2p6

Create ch-2.p6

1 files changed, 46 insertions, 0 deletions

diff --git a/challenge-015/ozzy/perl6/ch-2.p6 b/challenge-015/ozzy/perl6/ch-2.p6
new file mode 100644
index 0000000000..d13136e24e
--- /dev/null
+++ b/challenge-015/ozzy/perl6/ch-2.p6
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+#!/usr/bin/env perl6
+#
+# Vigenère-cipher encoder/decoder
+# Operates on capitalized input- and kextexts only
+#
+
+sub encode (Str $key   where { 'A' le $key   le 'Z' },
+            Str $plain where { 'A' le $plain le 'Z' })
+{
+    my $base            = 'A'.ord;                                                      # unicode base point of alphabet
+    my $column_index    = $plain.ord - $base;                                           # calculate col.index of plaintext char on encoding row
+    my $alphab_index    = (( $key.ord - $base ) + $column_index) % ('A'..'Z').elems;    # calculate alphabet index of cipher character
+    my $cipher          = ($base + $alphab_index).chr;                                  # convert back to unicode code point
+    return $cipher;
+}
+
+
+
+sub decode (Str $key    where { 'A' le $key    le 'Z' },
+            Str $cipher where { 'A' le $cipher le 'Z' })
+{
+    my $base            = $key.ord;                         # base/first letter of decoding row in Vignére table
+    my $column_index    = $cipher.ord - $base;              # column index of $cipher in Vignère table on decoding row
+    my $alphab_index    = $column_index % ('A'..'Z').elems; # zero-based index of column index into alphabet
+    my $plain           = ('A'.ord + $alphab_index).chr;    # convert back to unicode code point
+    return $plain;
+}
+
+
+
+sub MAIN (Str $cmd, Str $inputtext, Str $keytext )
+{
+    my %commands   = 'encode' => &encode,
+                     'decode' => &decode;
+
+    my &func       = %commands{$cmd};
+    my @inputtext  = $inputtext.uc.comb;
+    my @keytext    = $keytext.uc.comb;
+    my $outputtext;
+
+    for 0..(@inputtext.elems - 1) -> $i {
+        my $keytext_index = $i % @keytext.elems;
+        $outputtext ~= &func(@keytext[$keytext_index], @inputtext[$i]);
+    }
+    say $outputtext;
+}