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• #### Blog Post: Extracting GUIDs from a bunch of text

As part of messing with Windows Performance Recorder profiles, I had a need to extract everything that looks like a GUID from a blob of text. So I wrote this script. It digs through its STDIN and outputs all the GUID-looking things, uppercase-ized and sorted. https://github.com/mvaneerde/blog/blob...
• #### Blog Post: Perl scripts to encrypting and decrypt text using Rijndael

I talked about Rijndael in a few previous posts: Expressing a function f: GF(2⁸) → GF(2⁸) as a polynomial using a Lagrange polynomial , Generating the Rijndael S-box , Efficient multiplication and division in GF(2 8 ) , Sieving irreducible monic polynomials over a finite field , Addition and multiplication...
• #### Blog Post: Sieving irreducible monic polynomials over a finite field

Last time we talked about the addition and multiplication tables for GF(2²) ; GF(2 8 ) is relevant for the Rijndael encryption scheme. Joan Daemen and Vincent Rijmen use a representation of GF(2 8 ) where each element is a polynomial of the form b 7 x 7 + b 6 x 6 + b 5 x 5 + b 4 x 4 + b 3 x 3...
• #### Blog Post: Perl script to parse MPEG audio header

I've written a perl script (attached) which will parse MPEG audio headers and display them in a human-readable format. For example, if you run it on ding.mpeg (also attached) you get this output: >perl mpegaudioheader.pl ding.mpeg Frame header: 11111111 111 (should be all ones) MPEG Audio version...
• #### Blog Post: Perl one-liner: approximate pi via Monte Carlo method

http://programmingpraxis.com/2009/10/09/calculating-pi/ > perl -e"print 4/(map{\$n+=rand()**2+rand()**2<1}1..pop)*\$n" 5000 3.1336 59 characters , plus arguments.
• #### Blog Post: Bad Perl: locker problem

Bad Perl solution to the " print the open lockers " problem: perl -e"print join', ',map{\$_*\$_}1..sqrt pop" 100 54 characters. I prefer this to the 53-character solution obtained by omitting the space after the first comma. EDIT: 49 characters: perl -e"print map{\$_*\$_,' '}1..sqrt pop...
• #### Blog Post: Bad Perl: Josephus problem

Another programming contest asks to solve the Josephus problem . Bad Perl solution (83 characters... so close...) >perl -e" @_=(1..\$ARGV[0]);++\$c%\$ARGV[1]?\$i++:splice@_,\$i%=@_,1while\$#_;print@_ " 40 3 28 EDIT: got it down to 80. >perl -e" @_=(1..shift);++\$c%\$ARGV[0]?\$i++:splice...
• #### Blog Post: Bad Perl: Russian Peasant multiplication algorithm

I found this programming contest interesting: here's what I've got. perl -e " (\$a,\$b)=@ARGV;map{\$c+=\$_*\$b}grep{\$a&\$_}map{1<<\$_}(0..log(\$a)/log 2);print\$c " 7 19 I'm calling this a one-liner because the part between the quotes is less than 80 characters (75, to be exact.) The full...
• #### Blog Post: Good Perl, Bad Perl

One of my favorite languages is Perl . Perl has an ambivalent reputation; some people take to it, some accuse it of being a syntax-complete language. ( There's some truth to this. ) My view is that Perl gives you a very direct link into the mind of the programmer - much more so than other languages...
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