Search found 5516 matches

by Xanthir
Thu Aug 02, 2007 2:31 am UTC
Forum: Individual XKCD Comic Threads
Topic: 0297: "Lisp Cycles"
Replies: 86
Views: 23968

It may have something to do with the assignments they gave us. The only one I remember is that they told us 0 = x (not a typo, the number is being defined as a function that retruns x). Not that it matters, but that syntax looks suspiciously like ML and not Scheme. Its certainly not a Lisp language...
by Xanthir
Fri Jul 27, 2007 10:05 pm UTC
Forum: Mathematics
Topic: Discs problem
Replies: 20
Views: 3682

Oh crap, you're right. Sorry, I automatically assumed equal area.

I wonder if a fruitful direction would be to prove that the equal-area situation is always the maximal-diameter case for a given number of circles...
by Xanthir
Fri Jul 27, 2007 8:27 pm UTC
Forum: Coding
Topic: perl data structure
Replies: 4
Views: 1476

True. And that's why RE's probably won't cut it - PDAs are more powerful.
by Xanthir
Fri Jul 27, 2007 8:09 pm UTC
Forum: Coding
Topic: I need Standard Comics html
Replies: 14
Views: 3354

Nod. Don't use document.write. It's nearly never necessary. Instead, simply replace the appropriate dom elements directly. Something as simple as document.getElementByID('id').innerHTML = "<blah>stuff</blah>" would work. As well, don't use the code Gunfingers provided. ^_^ Using ta...
by Xanthir
Fri Jul 27, 2007 7:46 pm UTC
Forum: Mathematics
Topic: Discs problem
Replies: 20
Views: 3682

Hmm. Okay, well we know the most efficient circle-packing algorithm is simply the hexagonal one. I suspect that's what we'll want in order to minimize the radius overall. Now all you need to prove is that the maximum diameter across the packed circles is always decreasing, which I suspect. It should...
by Xanthir
Wed Jul 25, 2007 6:39 am UTC
Forum: Mathematics
Topic: Help my networking teacher
Replies: 8
Views: 2063

Crap, I didn't read the OP properly. Anyway, Yakk then answered it correctly. Logs are just a convenient way to get at certain properties of exponents. You can do everything you need to without using them if you pay attention to just what the log is doing at each step.
by Xanthir
Mon Jul 23, 2007 10:10 pm UTC
Forum: Mathematics
Topic: Help my networking teacher
Replies: 8
Views: 2063

2^(x-1) = 9^(x+1) Thus ln(2^(x-1)) = ln(9^(x+1)) leading to (x-1)ln(2) = (x+1)ln(9) And so x*ln2 - ln2 = x*ln9 + ln9 Thus x*ln2 - x*ln9 = ln9 + ln2 And x*(ln2 - ln9) = (ln9 + ln2) Finally x = (ln9 + ln2)/(ln2 - ln9) Just figure some logs and you're done. It required nothing more complex than the log...
by Xanthir
Sat Jul 21, 2007 12:42 am UTC
Forum: Mathematics
Topic: Really huge numbers
Replies: 30
Views: 4129

Yakk is correct. The point is not just to get a bigger number, but to find the most efficient and elegant way to generate larger numbers. Anytime you use lower-order functions, you're doing something wrong. Medium, for example, is bad. Why? Because it relies on constant (boo!) and linear (boo!) oper...
by Xanthir
Wed Jul 18, 2007 7:26 am UTC
Forum: Mathematics
Topic: Really huge numbers
Replies: 30
Views: 4129

Wikipedia explains Graham's number pretty well, but I"ll summarize. First, Knuth arrows. 3^^3 is equal to 3^3^3, or 3 raised to itself 3 times. So, 3^^4 would be 3^3^3^3, and so on. 3^^3 is equal to about 6 trillion. Skewes' number is much larger than this. (Skewes' number is approximately equa...
by Xanthir
Wed Jul 18, 2007 6:40 am UTC
Forum: Mathematics
Topic: Favourite Erroneous "Proofs"
Replies: 194
Views: 41594

Let S be a statement we wish to prove. Lemma (L): L => S. Proof: Assume for sake of contradiction that L is false. Then, L => S is false, i.e. "L and not S" is true. Hence, L is true. Contradiction. Since L is true, L => S is true. By Modus Ponens, S is true. L->S is still true when L is ...
by Xanthir
Wed Jul 18, 2007 6:36 am UTC
Forum: Individual XKCD Comic Threads
Topic: 0290: "Fucking Blue Shells"
Replies: 156
Views: 45567

The wife and I (along with my brothers on the second cart) finished Double Dash in about 20 hours. There was a small amount of sleep in the middle there, which we needed because we were stuck on 150cc Special Cup. When we woke up, we finished it on the first try with no problem. I've only avoided th...
by Xanthir
Mon Jul 09, 2007 8:26 pm UTC
Forum: Mathematics
Topic: number system questions
Replies: 61
Views: 8691

A little late, but... Yeah, the others are all correct. The essential difference between, say, extending your number system so that x^2 = -1 has a solution for x and extending it so that 1/0 = x has a solution for x is that, in the first one, you can create a structure that defines it and still obey...
by Xanthir
Mon Jul 09, 2007 7:48 pm UTC
Forum: Mathematics
Topic: Probability question for an RPG
Replies: 22
Views: 4263

I don't think it's possible to get an exact mathematical formula due to the way that rolling a 1 affects things. The entire thing basically runs in stages. First stage, you roll N dice. Count your botches (1s), pair them off with the highest possible dice above the success threshold and remove those...
by Xanthir
Tue Jun 26, 2007 4:31 pm UTC
Forum: Science
Topic: Physics question
Replies: 22
Views: 4514

Hawking radiation would seem to indicate that they are real. Of course, I don't know if we've ever observed the effects of Hawking radiation... However, I think we *have* been able to directly measure the effects of virtual particles in empty space. They provide a bit of a 'pressure', iirc. Or somet...
by Xanthir
Tue Jun 26, 2007 4:13 pm UTC
Forum: Science
Topic: Common misconceptions in Cosmology
Replies: 36
Views: 8037

Just as a quick comment, antimatter /= exotic matter. Hawking radiation depends on pos/neg particle pairs, not matter/antimatter pairs. I full understand that antimatter still has positive energy . The idea of Hawking energy is that in both cases as the particle becomes "real" it must have...
by Xanthir
Sat Jun 23, 2007 2:30 am UTC
Forum: Coding
Topic: Choosing a language
Replies: 92
Views: 14005

Of course, I'd then ask you, what *is* C's forte? ^_^
by Xanthir
Sat Jun 23, 2007 2:29 am UTC
Forum: Coding
Topic: Assembly... BUH BUM BAAHH
Replies: 90
Views: 22617

Unless you are designing a compiler, or doing something for which there is simply nothing *but* low-level code (like coding a microprocessor), there is absolutely no reason to ever learn assembly. Seriously. People who like to code assembly to make their code faster? Don't know what they're talking ...
by Xanthir
Sat Jun 23, 2007 2:13 am UTC
Forum: Coding
Topic: Choosing a language
Replies: 92
Views: 14005

Re: Choosing a language

I really can't believe only one person has commented on this... I have been doing programming in BASIC and tried Python and Ruby, but I'd like to really learn a real language. The choice stands between C, C++ and C#. Since when does the C family qualify as the 'real' languages? Python and Ruby aren'...
by Xanthir
Sat Jun 23, 2007 1:42 am UTC
Forum: Science
Topic: Common misconceptions in Cosmology
Replies: 36
Views: 8037

All right, so there's something that I've always wondered about with Hawking radiation, and maybe someone can explain it (or point me to where I can have it explained). Basically, Hawking radiation is caused by pairs of positive/negative energy particles that constantly appear and annihilate in extr...
by Xanthir
Sat Jun 23, 2007 12:57 am UTC
Forum: Mathematics
Topic: What the crap is a Hypercube?
Replies: 23
Views: 5450

As well, you can find the vertices, etc. iteratively. The formulas for each successive hypercube aren't difficult to puzzle out. Just start in the lower dimensions, where you can actually imagine what's going on. For vertices: Anytime you go up a dimension, you're just taking two hypercubes of the p...
by Xanthir
Sat Jun 23, 2007 12:31 am UTC
Forum: Mathematics
Topic: Next prime after A(4,2)
Replies: 19
Views: 5647

In case anyone's curious, A(4,2) is simply 2^^5-3, or 2^2^2^2^2-3 (evaluated right-to-left, of course). The Ackermann function actually maps easily to the hyper function: A(m,n) = hyper(2, n+3, m-2) - 3 Or, in Conway chained-arrow notation (which I like better for its extensibility): A(m,n) = (2 -> ...
by Xanthir
Tue Jun 12, 2007 8:30 pm UTC
Forum: Science
Topic: Why cant you go the speed of light with this method...?
Replies: 34
Views: 8819

Relativisitic effects aside, there's also a major flaw with this plan. Things accelerate by pushing off of other things and repelling them in the opposite direction (conservation of momentum). In the rocket's case, it is pushing off of fuel. If a large rocket were carrying a smaller rocket and the ...
by Xanthir
Tue Jun 12, 2007 8:06 pm UTC
Forum: Coding
Topic: Best language ever!!!11
Replies: 35
Views: 9783

adlaiff6 wrote:I thought ^^ was exponent.

You mean tetration.

Conway's chained arrows are much cooler, though.
by Xanthir
Tue May 08, 2007 12:18 am UTC
Forum: Mathematics
Topic: Division Induction
Replies: 16
Views: 8501

No problem. ^_^ Factorizing is usually the solution once you get stuck on anything greater than a linear equation. This is doubly true when dealing with modX stuff like you are, I've found.
by Xanthir
Mon May 07, 2007 11:51 pm UTC
Forum: Mathematics
Topic: Division Induction
Replies: 16
Views: 8501

k^2 + k
factorizes to
(k+1) * k

Either k or (k+1) must be even, and the other must be odd. Thus, the product is even. Thus, it is divisible by two.
by Xanthir
Mon May 07, 2007 11:38 pm UTC
Forum: Mathematics
Topic: Multiplication of a number in a non-10 base?
Replies: 26
Views: 10951

I did a comparison once of whether base 12 or base 16 was more convenient in terms of easy divisibility tests for common numbers. I gave the award to base 16 - it beat out base 12 by a long shot. It was about even with base 10.

Base 6, though, is probably pretty damn convenient.
by Xanthir
Thu Apr 26, 2007 7:45 pm UTC
Forum: News & Articles
Topic: This should be deleted
Replies: 7
Views: 2556

Nod. Longer life inevitably leads to more cancer. Nothing else is really required to explain this trend, though other factors may be influencing it as well. As soon as we stop being reproductively viable, there's little to no selective pressure against developing cancer.
by Xanthir
Thu Apr 26, 2007 7:43 pm UTC
Forum: News & Articles
Topic: Raptors Enjoyed Tea, archeologists claim
Replies: 34
Views: 8366

Raptors Enjoyed Tea, archeologists claim

Recently discovered cave paintings indicate a frightening level of development among raptors, as well as apparently overthrowing the long-held view that man and dino never coexisted. The mysterious link between raptor and British culture continues to confound, the authors' of the study report. http:...
by Xanthir
Sat Apr 07, 2007 10:50 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 0245: "Floor Tiles"
Replies: 252
Views: 67218

Oh, crap, I suddenly remembered that I *do* have a driving habit. Two related ones, actually. This will probably be a little weird. First, when you have a regularly broken median, I have to mentally bisect the area. This gets tricky when there are turn lanes and such shrinking some areas. I'll also ...
by Xanthir
Sat Apr 07, 2007 10:44 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 0229: "Graffiti"
Replies: 223
Views: 62548

For what it's worth, I've never found a better IDE for Lisp (my pet language) than Corman Lisp, which is Windows-only. It's one of two reasons why I have a dual-boot on my laptop. Otherwise I wouldn't use Windows at all. Now that we're here... For some reason, I can't get amarok to play my mp3s. I d...
by Xanthir
Sat Apr 07, 2007 9:48 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 0244: "Tabletop Roleplaying"
Replies: 212
Views: 45595

Yup. I'm a little shaky on the exact details, but basically photons only experience a single infinite instant. They are travelling at exactly lightspeed, so due to time dilation they experience absolutely 0 travel time between point A and point B, no matter how far apart the points actually are. All...
by Xanthir
Sat Apr 07, 2007 9:25 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 0245: "Floor Tiles"
Replies: 252
Views: 67218

I used to be very crazy about stuff like this. I'm a lot better now, but it still shows itself plenty. I had tons of rules about floors. Couldn't walk on black tiles or the lines connecting them (opposite of the comic's rule). Wall corners would extend lines that I couldn't cross. I forget exactly w...
by Xanthir
Wed Apr 04, 2007 4:07 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 0244: "Tabletop Roleplaying"
Replies: 212
Views: 45595

To those asking about places to play - try your local university/college and see if they have an RPG society. They'll probably know about local non-student groups too. As well, don't overlook online gaming. I use Roleplay Online and Groovy Gamers to get my gaming on, though there are plenty more si...
by Xanthir
Wed Apr 04, 2007 4:05 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 0244: "Tabletop Roleplaying"
Replies: 212
Views: 45595

Regarding recursion... I assume the rings are of equal size and that it's possible to shrink stuff in D&D. What would happen if you shrunk one ring and put it through the other? It would need to appear, smaller, through itself.. but it's still on its way through the other ring. My guess is that...
by Xanthir
Sat Feb 24, 2007 10:02 pm UTC
Forum: Logic Puzzles
Topic: Airplane On A Treadmill
Replies: 304
Views: 76909

i dont believe you.. science is flawed.. the plane wont take off... the wheels arent going to move at twice the speed of the conveyor if the conveyor is meant to match the speed of the wheels... in order for the plane to move the wheels would have to move faster than the conveyor... and i know perf...
by Xanthir
Tue Feb 20, 2007 3:27 am UTC
Forum: Logic Puzzles
Topic: Petals Around the Rose
Replies: 35
Views: 10636

Heh, took me longer to figure out how to play the game than to find the answer. Stupid UI... Got it in two tries once I started, though.

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