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Re: Polyglot (crypto)

by marcink (Monk)
on Jun 10, 2001 at 21:37 UTC ( #87320=note: print w/replies, xml ) Need Help??

in reply to Polyglot (crypto)

Just a couple of comments:

  • use arrays instead of all those ifs -- think about the problems you'll get into if you want to add,remove or change one of alphabet sets,
  • use for and foreach instead of array indexes -- they do the same thing with less code and less variables,
  • when accessing a single array element use '$text[$w]' rather than '@text[$w]' -- the first character tells Perl that you want to get a scalar (single) value, not an array,
  • use strict and -w (my generic advice ;-)),

And my attempt at rewriting your code:

#!/usr/bin/perl -w use strict; # One array instead of 2x8 if statements my @alphabets = ( "seklbvrfzijdqypcnowmtxuagh", "elbtjpwdvzqaorfiyxnukmghsc", "velukbiyxnordctjgpwhzqafms", "orsdvejwmcbiyhfzlukxntqgpa", "yxsdicvejqfbhmpluaorgkztwn", "ejqyxsdkziurgtwcaovfbhmpln", "jqyhcaxsdlkziuevfrgtwobmpn", "atdvnsirekmfqhwobjclgypxuz" ); my $dec = $ARGV[0] && ($ARGV[0] eq '-d'); # are we decoding? my ( $i, $out ) = ( 0, '' ); foreach ( split / /, <STDIN> ) { # read and split a single li +ne if ( $dec ) { eval "tr/$alphabets[$i]/a-z/"; # decoding tr/// # We need eval because tr/// + does # not allow for substitution +s } else { tr/A-Z/a-z/; eval "tr/a-z/$alphabets[$i]/"; # encoding tr/// -- as above +, # just reversed } $out .= "$_ "; $i = ($i + 1) % @alphabets; # this will walk through 0..7 circle } print "$out\n";

Update: I just noticed the 'reverse' operations in your code -- I skipped them during rewrite and yet the programs are compatible ;-) 'Reverse' does not modify its argument, so you probably wanted to use @text = reverse @text;


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[Cosmic37]: I try to match successive date times stored in variable $mydt
[Cosmic37]: I guess it is searching for the string "$mydt"
[Corion]: Indeed cool, erix ;)
[Cosmic37]: rather than the value of $mydt which is a date time strong such as 2016-01-01 12:30:56
[Corion]: Cosmic37: No, but maybe $mydt doesn't contain what you think it does, or it contains characters that are special in a regular expression? Try if( $line =~ /\Q$mydt\E/) { ... for a literal match
[Cosmic37]: I mean string grrr
[Corion]: Maybe add an else branch in which you print what the values of $line and $mydt are?
[Cosmic37]: ah thank you I will try
[Cosmic37]: you are right $mydt did not contain what I expected... :-D I will now think :-D
[Cosmic37]: crunch...grind... whirr...gnashing metal crunching cogs...

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