fail: (time, care) → fail

So, it was not uncommon for us in high school to randomly graph things against other things, usually as a form of humor, and sometimes as a form of venting frustration.  Especially popular was graphing variables against the fail-axis.

Frequently, we would graph "fail" versus things like time of day, time of year, weather, teacher, amount of homework, amount of Halo involved, how much coffee was available, side of the room you sat on, amount of time sleeping the previous night, volume of music... et cetera.  At the end of senior year, as a way or reminiscing, many of us would plot our Care vs Time Since Freshman Day 1 plots on the same plane to compare.

But now I'm in multivariable calculus, so no more of these petty 2-D constructions!  Here's my latest graph: it's basic, but it's a start.  Keep in mind that fail is not necessarily the reciprocal of care.

The average student tends to follow the path represented by a plane cut through the graph at any point such that the plane is normal to the origin.

Note that the more you study, the more you stretch the graph along the care axis... but no matter how much you study, enough time spent on an assignment will inevitably lower your care values and fail will go up.

+ 20 points to whoever can figure out why the paper is upside down.  I did it on purpose, and there is a good reason.

Finally, on a side note, I'd like to let everyone know that I did some research and that John McCain was assigned as an Ensign to the USS Enterprise on Stardate 14161.8.  However cool this is, though, it still doesn't make up for his Palinitis.  Read Araba's blog for some views on the almost-Ms. Alaska.

a poem.

As we drove along one day,
And gazed into the Sun,
You quoted Shakespeare, in my ear,
And changed the station, some,

And when we got there, to the park,
We laid down in the grass,
I rubbed your shoulders, soothed your back,
And you dozed off to sleep.

I watched you breathing to the beat
Of birds across the way,
But I wish I would have asked you if --

what i learned in chem oneohone

We learned about pressure today.

If by "learned" you mean reviewed from Nettles' class. I wish I could have skipped to 102.

By the way, assuming a theoretical compound Rhettium which is free from the effects of gravity (or, in Physical Science class, occasionally experiences a negative effect), you could experience similar pressure effects as you do in that UFO if you're floating in a Rhettium cloud 20 km away from the center of a black hole with mass 6.734 x 10²⁴ kg (and thus event horizon radius of 10 km) with an escape velocity of exactly c.

books and books... but mostly books

(Title half-stolen from Araba's blog.)

Oh my god... I had a shopping spree, this morning.  A book shopping spree.
Cooper Library (Clemson's main library) had a gigantic book sale this morning with incredible prices.  All hardbacks were $2, all CD's were $2, all paperbacks were $0.50, all magazines were $0.10, and I can't remember the rest but I do know that they were all $2.00 or less.

So I spent $23 or so.

Here's what I got.

Book #1: Encounters: an Introduction to Philosophy

Book #2: Elementary Differential Equations and Boundary Value Problems

Books #3, #4: Theory of Functions of a Complex Variable, Volumes I & II

Book #5: Analytic Geometry

Book #6: Modern Abstract Algebra

Book #7: Operating System Design: The XINU Approach

Book #8: Operating Systems: Concepts, Policies, and Mechanisms

Book #9: Vector Analysis

CD #1: Kiri Te Kanawa - Exsultate Jubilate (London Symphony Orchestra & Chorus) 

and CD #2: Birgit Nilsson - Wagner, Strauss, Verdi, Beethoven (Opera Gala)

Magazines: Mostly Scientific American, one National Geographic.

Now, let me tell a story about how hard it is to pull yourself away from such a book sale:

"One day, Matthew tried to pull himself away from a great book sale.  It was absurdly hard.  The end."

My suggestion?  Try to avoid news of book sales, because once you know about one you will undoubtedly spend lots of money there.

But hey, I actually kinda like what I bought, so there.

a summary of my psychic mechanisms

If you've seen my homepage, www.ces.clemson.edu/~mdaniel, you might have noticed that I claim to possess psychic ability.  Jimmy Mu challenged this claim tonight, and just clear everything up, I'd like to post a polished and edited FAQ we had.

Jimmy Mu: Dude, are you psychic?

Matthew Daniels: Absolutely!

JM: Read my mind right now!

MD: Sorry, I can't.  We have to be in relatively close range; you'd understand if you knew the mechanics of it.

JM: Well... can you read Rob's mind, since he's on campus?

MD: "BERR I LOVE STARCRAFT BUHDOH."  Heh.  Well, he thought that at one point, at least.  See, the thing is, thought waves -- or, more accurately, eddies, as we don't want to think of these as electromagnetic waves -- actually travel pretty slowly.  By the time I get a long range one, it may be pretty outdated.

JM: Tell us how you became psychic.

MD: Lots of pomegranate tea, actually.

JM: Are you sure?

MD: Well, no.  But that was the only significant lifestyle change I experienced leading up to my psychic abilities' manifestation.  There may very well have been other factors of which I was unaware.

JM: Matt, define "being psychic."

MD: Well, my brain has the ability to interpret radio-like waves which are ambient in the oosphere and which are transmitted from all sentient minds during the processes of conscious and unconscious thought -- but not during REM sleep.

JM:  Well, that's pretty amazing.  But can you predict the future?

MD: Only if I'm reading the mind of someone who can!  But who knows?  Maybe given enough time (and enough tea), I will.

JM:  How accurate are your abilities?

MD:  Well, I'm still perfecting them.  Right now, it seems that I only have a 50%-60% success interpretation rate.  I guess I'm still kind of tuning to the eddies' frequencies.  Oftentimes, I can finish sentences, know what people's plans are, or understand how they're feeling at the moment.  In the case of someone who's geographically distant, I might know what they were doing or thinking this morning (since the wave takes a while to catch up to me).

JM:  Cool!  Do you believe in other paranormal phenomena?

MD:  Not yet.  I've never contacted non-humanoids.  Unless, of course, you count yourself.

finding the gcd using the euclidean algorithm

Remember the GCD (or GCF) from our younger math days?  The greatest common denominator (or factor) seemed pretty retarded.  We never really used it... especially once we had calculators to guess and check for us (or until we all got our TI-83/84/89's and had a function to do it).

But as I hack and slash my way through the dense, unforgiving jungle of Deskin's Abstract Algebra (you'll remember that Mark gave it to me at my birthday, if you were there), I'm finding more and more reasons to think that basic math is cool.  The book is very hard to get through, extremely exact and unforgivingly precise and verbose... but the subjects are things like counting, finding GCD's and LCM's, and expressing integers.

So anyway, I came across the "Euclidean Algorithm" the other day, which basically helps you calculate the GCD of two numbers.  I'll summarize it here.

So suppose two numbers X and Y, and say that we want to find their greatest common factor.  In order for me to show do a simultaneous example with real numbers, let's call say that they happen to equal the integer values 320 and 144, respectively.

Before we calculate the greatest common factor, I need to make a quick segue and discuss the Divisor Theorem.  Another formalization of 3rd grade math, the Divisor Theorem says that the following expression holds for all integers a, b, q, and r, such that b > a > r:

b = aq + r

In 3rd grade terms, b divided by a equals q remainder r.

So with that in mind, let's return to our original problem.  Suppose X > Y (and it is, as 320 > 144).  Then we can create the expression:

X = Y*q1 + r1   |   320 = 144*q1 + r1

Right?  Of course we can, because those are all integers.  So a little third grade division tells us that our numerical example resolves to:

320 = 144*2 + 32

Now, watch this:  we're going to forget X, make Y the largest number, and make the old remainder the new quotient.  Then we'll add a new remainder:

Y = r1*q2 + r2   |   144 = 32*q2 + r2

Now we just solve this in the same fashion:

144 = 32*4 + 16

We follow the same variable shifting pattern (try writing these equations in order on your paper and using arrows to show how the variables move right to left as you go down.  The arrows should end up being diagonal lines from the top-right to the bottom left.):

r1 = r2*q3 + r3   |   32 = 16*q3 + r3

If you understand the pattern we're following, then good!  You know how to use this algorithm.  If not, you're screwed, because we're basically done.  Note that in the above example q3 = 2 and r3 is exactly 0 (because 16 is a factor of 32).  This means we're done!  The number that q3 is multiplying (here, r2=16) is the greatest common factor of the original numbers.  That's it!

Basically, you would keep following this pattern until you got to evenly dividing numbers such that the new remainder is zero.  The greatest common factor of the original X and Y is exactly the number in the position where Y started out.  When I say exactly, what I'm trying to say is that... that's it!  It's not possibly some multiple of that; that is the answer.

More later on how every integer can be expressed in the form ax + by = c, where all those numbers are integers.  It has a lot to do with greatest common factors.

Final note:  the greatest common factor of two numbers A and B is often expressed as (A, B).  This should be easily distinguishable from an ordered pair by the context it's used in.

newsflash: e&m receives several beatings in its old age

By beatings, of course, I mean hits.  And by hits, of course, I mean pageloads.

And by E&M, I mean my mindmap posts I made quite a while ago.  Remember those? This one was of a Dr. Mills lecture (and is the only reason I got a 5 on E&M), and this one was on a lecture by Mr. Newton.

So a while ago, I installed this hit counter widget on my page.  Don't go looking for it outside of the source html; it's just some embedded code.  But it lets me go to statcounter.com and see how many hits I get everyday from where in the world. It's pretty neat, actually!  I've had hits from all over the world:

So yeah!  That's pretty cool.  And the thing is, all these foreign people are coming off of google searches on E&M topics.  In fact, as of this posting, I'm the 5th result if you google "lectures about current resistance".  Try it and tell me if it still works!

Anyway, so I suppose if I want more hits, I should write more on E&M.  But I don't really feel like it, you know?

More to come.  Hold tight.  Comment.  And if you'd like to help me expand my userbase, you should link, blog about, digg, or otherwise propogate links to my blog.  It'll be fun!

Oh, and as of now, I've decided to end all comments of mine with a series of lucky numbers (see the comments on the immediately previous blog entry to this one to know why).  So if you see that convention somewhere, just know that it was my idea.

the truth about not-charleston

I had two significant online conversations last night (significant meaning I cared and they were longer than 10 lines): one with Araba, and one with Jackson.  Both were on the same subject.

I told Araba that "Mrs. Dobson is haunting me".  If you weren't in AP French or AP Fizz, you wouldn't understand. She would come in the room with a visitor and point to everyone around the room: "Arielle is going to Brown, Miguel is going to Stanford, Sally's going to Princeton, Araba's off to Harvard, Matthew's..., Sherwin's going to Yale..."

It was like that every fucking time.  She could not deal with the fact that I was going to Clemson.  I don't know why; I wasn't in the top ten or anything.  Perhaps it was because of the people I was always contrasted with by taking advanced classes.  Whatever it was, she could not deal with the fact that I was just going to Clemson.

Anyway.  I dunno.  I figured that for an undergraduate program, it didn't really matter where I went, right?  Multivariable calculus is pretty universal, and so is physics.  For undergrad courses, I would get the same education at any reasonably accredited institution.

And I'm probably still right.  But what I didn't think about was the people who I would be surrounded with, shaping my education in ways outside the classroom.  As I note in the excerpt below from my and Jackson's chat (which is released under the Creative Commons 2.0 License), I miss being surrounded by people who have this insatiable urge for progress.  I miss people who write poetry for the sake of writing poetry, who prove odd theorems for the hell of it, people who are researching a topic on wikipedia before you can finish the prompting sentence, and people who can't put down their cameras until they've stuffed their memory cards to the brink with photos to sift through.  I miss people who strive for self-betterment, and who are passionate about their passions.  Perhaps I simply miss people who have passion, in general.  As Jackson notes, it is "the undeniable truth that mediocrity vastly outnumbers drive and unique ability."

Maybe it isn't better in other places, and to be honest, it isn't that bad here.  Seriously, don't get me wrong; I really do love Clemson.  It's just that key cultural aspect that I sorely, sorely miss.

Maybe it isn't, but maybe it is.

Hmm.  Please comment.

=== Conversation Excerpt ===

me: We actually have a pretty low smoking rate, actually.

marijuana, that is.

about 15% I think.

although our drinking rates are absurd.

15% regular smokers, that is.

jackson.holder: I mean, I know. The WW kids might run around in a fog, but all you high achievers are gonna experience fatal liver failure at 28.

me: High Achievers?

Man, Jackson. Let me tell you.

I love it here.

But I am, occasionally,

Slapping myself pretty hard for not reaching higher.

I dunno. I dunno what to think about it anymore.

jackson.holder: hate to say you should have applied to MIT. Fortunately I don't have to, because I already did like 40 times.

me: Hate to say I wouldn't have made it into MIT. But it does stand to reason that I could have made it into Duke, or Davidson, or Yale, or something.

Maybe Emory, I dunno.

Maybe even Brown.

I guess I'll never know.

jackson.holder: not necessarily true.  

If you feel strongly about it you can always apply.

me: I don't feel strongly about it.  

It just lingers in the back of my mind, and pokes me occasionally.

jackson.holder: well then yes I suppose it is pretty late.

yeah it'll do that.

I know what you mean exactly.

me: I think the reason it's bothering me isn't the school so much as the people.

I mean.... I guess I was incredibly lucky with my friends.

People from all sides of my life in Charleston were esoteric poets and adventurous intellects.

Almost everyone had some sort of fervor in a particular field or subject, and loved what they did.

My magnet friends and my SOA friends.

jackson.holder: mmmyes.

me: And it seems like most people here are just sorta mreh.

jackson.holder: and now you are faced with the undeniable truth that mediocrity vastly outnumbers drive and unique ability.  

that very few people get the education you did, or got to experience the culture you experienced

me: Yeah.

jackson.holder: and that without the drive that a place like charleston and a community like ours provides, many people understand life to be a simple trial and reward system. A little work, a little alcohol.

  

pretty depressing.

me: Depressing indeed. I guess I just need to make sure it doesn't happen to me.

And the people I care about, if possible.

You know, you worded that all very well.

Do you mind if I reproduce it?

jackson.holder: go for it.

me: Under Creative Commons or something?

jackson.holder: just fucking jack it, call it yours, I don't care.

me: lol.

jackson.holder: I've had plenty of time to think about it.

me: Thanks, Jackson.

jackson.holder: it's realizations like this that changed me, matthew.

reviewing: "π - Faith in Chaos"

So two weekends ago when I visited Charleston, by 4th grade teacher and long friend Mrs. Fisher sent me an off-to-college card with a Best Buy gift card inside.  So Saturday night, Anastasia and I went on a shopping spree, and I bought - among other things - a Darren Aronofsky Collection with two movies: Requiem for a Dream (the movie which prompted me to buy this collection) and π.  I had seen Requiem for a Dream before; it's a little disturbing, but it's a great movie.  I'm sure that if we showed it in middle school, teenage drug use would decline.

But I had never seen π before, and the low price of the collection prompted me to buy the set.  Last night, I watched it with Karen and Sammy.  It was... okay.  I loved the concept; a mathematician obsessed with finding order in chaos, and convinced that the entire universe and everything in it can be perfectly described with mathematics.  Thus, he tackles one of the most chaotic systems in history: the stock market.

Already slight off his knocker, his attempts at ordering the stock market - and, later on, using similar patterns to find the true name of God - are unsuccessful, although he does come very close (there are hints that he actually does understand the patterns, but, even if this were so, he is unable to apply them to any real problems).  Between his existing mental problems, the pressure of sorting through the disorder, and the consistent attacks by organizations - both religious and corporate - leeching off of his talents for their own good eventually do him in.

So it was a pretty good movie... until I heard something wrong.  As soon as I heard it, the rest of the movie lost its reality and truth that normally makes movies really hit hard with me.  The issue was when he referred to the golden ratio (which, for the curious, is exactly equal to (1+sqrt(5))/2) as theta.  I've actually done lots of reading on the golden ratio and on sacred geometry in general, and I have never, ever seen it expressed as theta.  Traditionally, it is represented by the greek letter phi.

Instantly, I knew something was up.

He also used the Fibonacci sequence in the movie, and claimed that 233/144 approaches phi (which he again expressed as theta).  While it's true that the limit as t→∞ of F(t)/F(t+1) does approach the golden ratio, 233/144 doesn't approach anything.  It's just 1.6180555555..., which is a static number very close to, but certainly not equal to, phi.  And it doesn't approach anything; it just is.

Anyway, I'm sure there were plenty more math errors.  One thing that particularly bothered me was that this brilliant number theorist who nearly predicts the future of the stock market was, at one point, pondering A=πr^2 and C=πd on the train, as if they held mythical truth.  As a matter of fact, wtf is this movie even called π?  It had nothing to do with circles!  He did find some golden spirals, but then the movie should be called Φ, not π.  I dunno.  The title confused me by the end.  Those basic area and circumference equations were the only real reference to π, except of its basic nature as an irrational number.

Anyway, if you watch it, let me know what you think!  Despite my mathematical distress, it was, overall, a pretty okay movie worth watching once or twice just so you can say you did.  And, in a brilliant stroke of coolness, it's in black and white!

can i switch to linux?

Yes, you can!

I'm a pretty big advocate of open source software (OSS) and Linux, so I figure I'll start adding it to my list of bloggable topics.

I stumbled upon this article today in the Coffee Room at LinuxForums.org.  I think it's a particularly great pro-Linux article because the writer isn't (as I understand it) a particularly tech-savvy guy.  He's certainly not my grand mother, and he knows his way around a computer, but what I'm saying is that he probably can't write something in C.

And the best part is, that okay!  Linux works great for him, and not only is his work more streamlined, error-free, productive, and free, but he also likes the mentality that comes with using nearly all OSS, developed by software hackers around the world.  He likes that they're driven by the urge to want to create a great computer system instead of by market forces.

So anyway, if you're still using Windows, give the article a quick browsing over.  You never know; installing Linux may be the next best thing to happen to your computer.

Article: http://www.lewrockwell.com/orig9/coleman2.html

$ man punching

How do you throw a proper punch?  What's all this internal energy stuff they talk about in martial arts?  Here's the first half or so of an article I'm writing to explain.

  Directing Energy in Your Martial Arts

  ----       Matthew Daniels       ---- 

|=======================================|

If there is one thing that seems to frighten and temporarily alienate newcomers to the martial arts, it seems to be noise.  The kiai we often see in the Japanese arts is a prime example.  Often, a new student will feel out of place when asked to kiai, and may sometimes refuse to kiai for weeks into their training.  Even among those who do not refuse, it is not uncommon for the more arrogant students to snicker behind their instructor's back at the idea of a kiai.

But for the advanced student, the kiai is no longer only a noise; in fact, one might eventually feel that the kiai is not a noise at all, but happens to produce some involuntary sound as a consequence of an energetic explosion which drives the power behind their motions.

When a student begins to realize that a kiai is, indeed, not a noise at all, he has probably started to understand the importance of energy management in his chosen art.

I - and my instructors, before me - will sometimes ask students where their punch begins and ends.  To a white belt, this may seem a nonsensical question; the fist, of course, travels from the ribs to the desired target (the opponent's solar plexus, for instance).

Obviously, this is not the answer that an instructor is looking for.  The punch should start not from the ribs, but from the ground.  For some students, this will initially seem confusing, but it is certainly true.  The energy that drives your fist should start from the heel.

As a punch is executed, the heel should push against the ground.  Imagine that the path of your body between the heel and the knuckles is a large canoe resting against a riverbank (the ground).  From a standstill, can you simply begin to paddle and expect the canoe to move?

Well... actually, you can.  And sometimes, there's nothing wrong with this.  This is called punching from the shoulder.  But would it not be faster and more powerful to push off of from a sturdy riverbank, getting your momentum going before you begin to paddle?  This is called punching from the heel.

A convenient way to practice energy concepts like this one is to visualize the energy transferring through your body in real time, as you're punching.  The Chinese traditionally believe in the concept of chi, an energy-like substance which permeates the body and the world, providing a sort of life-force.  Fully appreciating the concepts of chi and the Chinese philosophies behind the different energies at work in the cosmos and inside the human body is far, far beyond the scope of this article.  For now, to illustrate my ideas about energy in your martial art, we will make the gross assumption that chi is a homogeneous, energetic fluid that can be directed and harnessed by the body.

So, in the previous example, can we draw energy like this from the ground?  Yes, we can; and you should, if you wish to generate a respectable amount of power in your attack.  If you visualize the energy transfers at work in your body, it can help you attain this energy channeling and put your whole body in sync with your attack.

Let's run a basic trace of this energy as it travels from the Earth and out of your fist.  For our purposes, the Earth is not moving; it provides an eternal riverbank to shove off of, and is a limitless source of energy.  Therefore, when appropriate, we should always try to use it to our advantage.  To do this effectively, we must root ourselves into the ground; this is one application of your stance training.  Try to imagine your feet reaching down into the ground, locking themselves in place by becoming part of the Earth.  These roots will help ou soak up the energy that will drive your fist.

As you shove off from the heel (without losing your root), the energy will being to travel up the legs.  As it reaches the waist, two things should happen simultaneously.  The energy should being to torque the waist and hips.  It turn, the waist and hips will accelerate the energy up the body and into the spine.

As the energy travels up the spine, a similar reaction will take place.  The energy will excite the spine, causing a wave through it and up the back.  Your chi should ride this wave up your body (along the fire path), and it will be thrown out of the spine and into the arm.  

perlmwdtut(0)

A tutorial for those new to Perl but not to Programming: Part 0

Introduction

When you don't have much to blog about, you start trying to think about things you already know.  Well... I know Perl, and I have some friends who would like to learn it, or at least be comfortable with it.  I'll present this tutorial in progressively more advanced parts, showingcasing a little at a time the high and low points of Perl and how to use it.

What is Perl?

Perl is lots of things to lots of people, but to me - and many other people - it's a swiss army knife language (if you will).  When you pull a bunch of random data out of an excel spreadsheet and you need to do some stuff with it real quick (like, maybe, remove invalid email addresses and then send a mass message), you don't compile a huge C application and you don't need to power up your Java VM.  You just write a few lines of Perl.

Perl has had other purposes, too.  Sometimes referred to as the glue that holds the web together, Perl has been used extensively throughout the years in CGI scripting, although it is my believe (but not quotable experience) that it is falling out of use with the evolution of the internet into a far mor

e interactive and m

ultimedia-oriented experience... although I also know that there is still plenty, plenty, plenty of Perl out there.

Perl is also great for just hacking things together and making things work.  If you had a round peg, a square hole, and a pocketknife, Perl would be that pocketknife.  Observe this comic from xkcd.com (released under Creative Commons; kudos to Randall Munroe for his amazing webcomic):

(Click for larger view.)

Anyway, that's about what Perl is.

Jumping Right Into It

No tutorial would be complete without...

#!/usr/bin/perl

use warnings;

use strict;

print "Hello, world!";

There's our familiar Hello, world! program.  The first three lines are unnecessary, generally.  You could write the program as simply print "Hello, world!";, execute perl and it would work just fine.  But if you're curious, here's what those first lines are all about.

Line 1: #!/usr/bin/perl

This line is often called a shebang, and is common to many Unix scripts.  In fact, if you go find a bash script on your computer, chances are that the first line is something like #!/bin/sh.  That's because when you run chmod +x script.pl to turn your script into an executable file, it looks as that first line to determine what needs to be called to run it.

Of course, if you're running Windows, none of this will make any sense.  If, for some reason, you are in a Windows system, this first line won't help you out much.  Just run your scripts using the perl syntax and everything will be okay.  Depending on your Perl interpreter (I know that ActivePerl works this way), you could also just double-click on your script in Explorer and it should run.  Be wary that if you're script isn't actually doing anything functional - for example, if it's just the Hello, World! script above - then you probably won't see anything happen besides a terminal appear for a few milliseconds and disappear again, because the terminal's process will die along with the Perl script.

But be warned that if you're running Windows, you probably won't be able to use a lot of the things in this tutorial.  Go use Visual Basic or something.

Anyway...

Line 2/3: use warnings; use strict;

The use of the warnings module alerts us when we do silly things.  It won't stop our program from running, but it might let me know if, say, I declared a variable I never used.  Sounds stupid?  Not really.  Perl is extremely nice to its user and tries to do exactly as it is told... which can be a problem.  Say I have the variable $rest = 5; and then later on I mistype it: for ($x=0; $x<$breast; $x++)....  Normally, an interpreter/compiler would catch this Freudian slip (perhaps you had some inappropriate browser windows open while coding), but Perl will do its best to do exactly as you say, so it'll instantiate $breast for you with the default value of 0.  This will not function correctly.  Using warnings will probably give you a little wake up call if you knew this variable was supposed to be in use.  This is only an example, though; the warnings module is extensive and highly useful for debugging.  The use strict flag makes you declare all variables with a some sort of scope modifier, which we'll talk about later, but it is important to note that, unlike many languages, a variable declared in any scope will, by default, become global.  This often causes trouble if not handled with care.

If you can't figure out line 4, you probably shouldn't be reading a tutorial for people who already have some programming experience.  In fact, you should probably understand line 4 whether you have programming experience or not.

Variables

Watch this:

$variable = 5;

$variable = "Hello, Janet!";

$variable = \$referenced_var

$variable = \&referenced_subroutie

$variable = -234.3

$variable = 0x0000003f;

$variable = "Some other data type!";

print $variable; # prints out "Some other data type!"... and yes, this is a valid program.

# By the way, this is a comment!

Perl has a what's called a dynamic typing system.  Several other languages have this as well (Ruby and Python, to name two) but it isn't typical of what you see in C, C++, or Java.  Whereas in those languages you must declare a variable's data type (either beforehand or on-the-fly), Perl variables can hold any type of data, any time... the only restriction is on memory (which, these days, is considerable).

Note: Perl 6 (which will be similar but also considerably different from Perl 5 and earlier) will have an exciting new hybrid typing system which allows you to assign a value if you want to.  For example, you could write the traditional, perlish: $variable = 5;, but you can also write the sometimes useful and more C-ish: int $variable = 5;, which will treat $variable just like C would.

More to come later!

aesthetic astronomy

My old notes were hard to read?  Well, I made them into a nice PDF with Lyx.  Here's the result.  Point your browser to:people.clemson.edu/~mdaniel/AstrNotes.pdf.

I'm working on a way to embed the pdf right here. Open to suggestions.

-Matthew