The source code of the script used to generate the images is available here.

Get the code here.

$ time python mandel.py > \dev\null
real	0m0.051s
user	0m0.036s
sys	0m0.010s
$ time perl mandel.pl > \dev\null
real	0m3.518s
user	0m3.463s
sys	0m0.029s

You can find the code here.

This script works well for zooms, as long as you stay below a few thousand iterations. The following picture was generated with x=-1.1887204, y=-0.3032472, width=0.01 and 150 iterations.

Just Another Perl Hacker

I figured that it was about time in my hacking career (read: I was bored enough) that I should make a japh script. After a couple attempts I came up with this:

#!/usr/bin/perl
while(<DATA>){
 	for (map{ord($_)-33}split ''){
		$__++;
		$_||(print(chr($__+19))&&($__=0));
	}
}
 
print "\n";
 
__END__
                   /|                        |\
      !            ; :                        : :
                  | Y,                      ,P |
     !             |  Yb.        __        ,dP  |
                  l\  YMMb,_ _,/  \,_ _,dMMP  /f
  !                 j;  `YMMP'  `--'  `YMMP'  ;j
                   : \   YP`-._    _.-'YP   / ;
  !            !      \ `\,  _,\_    _/,_  ,/' /
                     `,_,   \`o>  <o'/   ,_,!'
                         `\            /'
                           |  _    _  |
      !                     / 88b  d88 \
                           \ `8P  Y8' /``-.
             !               `\,    ,/      \
                             _`----'        \
                  !        _.'/ '          `, \
                        .'_,'_..._          \ ;
       !               .',/.dMMMMMMb. |      /  \
                    .'./.MMMMMMMMMMM ; !    /    ;
                   / /.MMMMMMMMMMMMM/     /     ;
                  | ;dMMMMMMMMMMM!P/'   ,/'   !    ;
                  |/dMMMMMMMMMP'     .'          |
   !               ;dMMMMMMMMM|     _/            |
                 ;dMMMMMMMMMMb_|_!| /;            ;\,
                 dMMMMMMMMMMMM`M`M`;.---..      '   `\,
                :M!MMMMMMMMMMMMMMMP/'     `\            \
               /|MMMMMMMMMMMMMMP/          \    _!_      `.
  !            / |MMMMMMMMMMMMMM|            |.-'  `-._    \         .'\
             ;!  ;MMMMMMMMMMMMMM|            :         `-._ `-.     /  _\
             |   ;!MMMMMMMMMMMMM;            |             `-. `-.._.'/
              \   `\YMMMMM!MMMP/'\           |                `~~----'
               `-._, ``YMMMP'_.-'\         ! ;_
                 |      /         `-.,_./     7
                _/    `\,    !        /      _/
             ,-' ,  ,   /         _.'      /
            (_(_(__(__.'       !,-'        /
                              (__(__(_(_/'

Download.

I’ll let you go ahead and figure it out on your own. It’s not super-hard, but it’s fun.

Mandelbrot

In another fit of boredom I decided that it was finally time to create a mandelbrot set renderer. I originally tried to make one of these in basic, long before I had the math to do so. I was proud that I got the real axis to render, and figured it was time to complexify it. To keep things simple I decided to make it render an ASCII-art version of the set that would fit in a terminal window. The output looks like this:

                        ...............................:::::oo@@@@o::::..........
                      ...............................::::::O@@@@@@@@o:::::.......
                     .............................::::::::oO@@@@@@@@o::::::::....
                   ...........................::::OOO8ooO@O88@@@@@@8@O8o::::Oo:..
                  .......................:::::::::o8@@@@@@@@@@@@@@@@@@@@OO@@@@::.
                 ...................:::::::::::::oOO@@@@@@@@@@@@@@@@@@@@@@@@@o:::
                ................:::::::::::::::o@@@@@@@@@@@@@@@@@@@@@@@@@@@@Oo:::
               ..............::::@oo::oOoo:::ooo@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@8o:
               ...........:::::::oO@@@O@@8@OooO8@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@O::
              ..........:::::::::oO@@@@@@@@@@88@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@::
              ........:::::::8ooO8@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@o::
              .:::::::::::::oO@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@o:::
              @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@Oo::::
              .:::::::::::::oO@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@o:::
              ........:::::::8ooO8@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@o::
              ..........:::::::::oO@@@@@@@@@@88@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@::
               ...........:::::::oO@@@O@@8@OooO8@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@O::
               ..............::::@oo::oOoo:::ooo@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@8o:
                ................:::::::::::::::o@@@@@@@@@@@@@@@@@@@@@@@@@@@@Oo:::
                 ...................:::::::::::::oOO@@@@@@@@@@@@@@@@@@@@@@@@@o:::
                  .......................:::::::::o8@@@@@@@@@@@@@@@@@@@@OO@@@@::.
                   ...........................::::OOO8ooO@O88@@@@@@8@O8o::::Oo:..
                     .............................::::::::oO@@@@@@@@o::::::::....
                      ...............................::::::O@@@@@@@@o:::::.......
                        ...............................:::::oo@@@@o::::..........

The code’s far from polished and not what I like to publish, but it’s a fun thing to look at and offers you some neat abilities to poke things around and fix some pesky problems that just need clear thinking applied to them. It’s available here.

• A fitness function, that determines which individuals are most fit to reproduce
• A mutate function, that will add random chance into each generation
• A breed function that allows the best individuals to reproduce.

I ended up implementing a very simple algorithm, but it’s fairly fast and very generic – it can be easily adapted to just about any task. Sadly, I have no fascinating application just yet, but if I stumble across one, I’ll be sure to post about it.

After the jump, I’ll put up some of the code I used and a link to the script, all for your viewing pleasure.

The heart of the algorithm is the mutate and breed functions:

[sourcecode language='php']sub mutate{ # Mutates each allele of an individual by a random, weighted amount,
# controlled by certain parameters. It re-initializes if the allele
# is zero, and takes abs()
my $ind = shift;

for (@$ind) {
$_ = eval($init_string) unless ($_);
$_ += (rand(2) – 1)*($mut_weight*($_)+$mut_offset);
$_ = -$_ unless ($_>0);
}

return 0;
}

sub breed{ # Breeds each individual with the top 20 percent of the population randomly
# by averaging each allele of the individual with the corresponding allele
# of a random individual in the top quintile. Note that this means that
# each individual breeds with, at most (and ideally), as many individuals
# as it has alleles, which breaks down the parent / child model slightly.
my $indvs = shift;
my @list;
($minimize) || (@list = sort {fitness($b) fitness($a)} @$indvs); # Sort asc. vs. desc.
($minimize) && (@list = sort {fitness($a) fitness($b)} @$indvs);

@list = @list[1..(int(scalar(@list)/5)+1)];

for (@$indvs) { # Iterate through individuals
my $ind_ref = $_;
my $i = 0;
for (@$ind_ref) { # Iterate through alleles
$_ = ((@list[int(rand(length(@list)-1))])->[$i] + $_)/2; # Average given allele with
# a random, fit,
# corresponding allele
$_ = (rand(1)<$reset_prob?eval($init_string):$_); # Re-init the allele some
# percent of the time
$i++;
}
}

return 0;
}[/sourcecode]

Between the comments and the code, it should be pretty clear what's going on in here, although some of the data structures are kinda hard to get from this section. As I explain in the code:

A randomized population is created. An array holds references to the specified number of “individuals”. Each individual is an array of alleles (scalar values) that are chosen by evaluating a specified string. These are currently positive real numbers.

These references (or references to the population array) are passed as arguments to the functions each iteration.

If you’re interested, be sure to check out the code and please give me some feedback!

UPDATE: Ivan in the comments made the recommendation of using an anonymous function to intialize individuals. I made that change he recommended and updated the code.

To start, installing Finance::Quote is a breeze. As long as you have CPAN installed, just type at the command line:

$perl -MCPAN -e shell
>install Finance::Quote

From there it’s easy to get start, it’s just a matter of importing the module and creating and instance. This means the beginning of our script will look like:

#!/usr/bin/perl -w
use strict;
 
# import module
use Finance::Quote;
# create object
my $q = Finance::Quote->new();

The instance that we created has one main method: fetch(). It takes a list of arguments, with the first being a the exchange to look for quotes on, and the remaining being a list or array of ticker symbols. The Finance::Quote documentation provides the following list of valid exchanges:

australia           Australan Stock Exchange
dwsfunds            Deutsche Bank Gruppe funds
fidelity            Fidelity Investments
tiaacref            TIAA-CREF
troweprice          T. Rowe Price
europe              European Markets
canada              Canadian Markets
usa                 USA Markets
nyse                New York Stock Exchange
nasdaq              NASDAQ
uk_unit_trusts      UK Unit Trusts
vanguard            Vanguard Investments
vwd                 Vereinigte Wirtschaftsdienste GmbH

For the purposes of this script, I’m going to stick to “usa” because it covers both NYSE and NASDAQ, and those are the stocks I’m interested in.
Fetch() returns a two-dimensional hash of results. The first index (or dimension) is the ticker symbol of the stock and the second is the label for the specific piece of information. For now, the labels that we’re interested are the name of the company (‘name’) and the price (‘price’). A full listing of labels is available in the Finance::Quote documentation.
Using this information we can now build a simple script to fetch a stock quote:

#!/usr/bin/perl -w
use strict;
 
# import module
use Finance::Quote;
 
# create object
my $q = Finance::Quote->new();
 
# retrieve stock quote
my %data = $q->fetch('usa', 'GOOG');
 
# print price
print $data{'GOOG', 'price'} . "n";

This script, although it does what it’s supposed to, isn’t very pretty. By adding a little code to read ticker symbols from the command line we can check on multiple stocks at the same time, as well as remove the need to hard-code the ticker symbols. We can also make it produce much prettier results by adding more information about the company and add some basic error checking, which yields the following script:

#!/usr/bin/perl -w
use strict;
 
# import module
use Finance::Quote;
 
# create object
my $q = Finance::Quote->new();
 
#print usage information
if (length(@ARGV) == 0) {
	print "Usage: $0 ticker1, ticker2, ... , tickerNn";
	exit;
}
 
# get stock symbols from the command line and
# format them correctly (uppercase)
for (@ARGV){
	$_ = uc();
}
 
# retrieve stock quote
my %data = $q->fetch('usa', @ARGV);
 
# print result for each stock
for (@ARGV){
	if ($data{$_, 'success'}) {		# if getting the quote succeeded
		my $name = $data{$_, 'name'};	# build a report
		my $price = $data{$_, 'price'};
		my $message = '';
		$message .= $name . ' (' . $_ . ')';
		$message .= ' ' x(25 - length($message));
		$message .= "$$pricen";
		print $message;
	}
	else { print "Failed to retrieve quote for $_: $data{$_, 'errormsg'}n"; }
}

This is very simple, but it does its job well:

$ quote goog msft aapl dell java
GOOGLE (GOOG)            $352.32
MICROSOFT CP (MSFT)      $22.32
APPLE INC (AAPL)         $98.23
DELL INC (DELL)          $11.99
SUN MICROSYSTEMS (JAVA)  $4.54

Download the script here