Search found 3691 matches

by PM 2Ring
Wed Aug 10, 2016 2:22 pm UTC
Forum: Mathematics
Topic: Math: Fleeting Thoughts
Replies: 434
Views: 152030

Re: Math: Fleeting Thoughts

Well done, jaap!

Flumble wrote:No worries, I also know brain farts.

:) Thanks for reminding me of the Goat Problem; I've just added some diagrams to that thread.
by PM 2Ring
Wed Aug 10, 2016 2:19 pm UTC
Forum: Mathematics
Topic: Trickier problem than it seems. (goat in a circular paddock)
Replies: 19
Views: 5347

Re: Trickier problem than it seems. (goat in a circular paddock)

I've created a diagram in SVG for this puzzle. Here's the SVG code. Just save it to a file with the .svg extension and you can view it in your browser. <?xml version="1.0" encoding="UTF-8" ?><svg xmlns="http://www.w3.org/2000/svg"    xmlns:xlink="http://www.w3.org/1999/xlink"    width="400" height="...
by PM 2Ring
Sun Aug 07, 2016 2:00 pm UTC
Forum: Mathematics
Topic: Math: Fleeting Thoughts
Replies: 434
Views: 152030

Re: Math: Fleeting Thoughts

For the 3D case, the segments are unit vectors in the X, Y, and Z directions, and the oppositely-directed unit vectors -X, -Y, -Z. I think the OP is asking for the more general case where the segments are not necessarily axis-aligned. indeed (wait, am I "OP"? after 9 pages?) Ah, right. :o...
by PM 2Ring
Sun Aug 07, 2016 5:40 am UTC
Forum: Mathematics
Topic: Math: Fleeting Thoughts
Replies: 434
Views: 152030

Re: Math: Fleeting Thoughts

But does it also work for odd numbers n=2k+1>4? My gut feeling says no for at least n=5, but I can't prove it (at this time). Also, does adding dimensions have any effect? Your gut feeling is correct, and adding more dimensions doesn't help. For the 3D case, the segments are unit vectors in the X, ...
by PM 2Ring
Fri Jul 22, 2016 9:26 am UTC
Forum: Mathematics
Topic: Trickier problem than it seems. (goat in a circular paddock)
Replies: 19
Views: 5347

Re: Trickier problem than it seems. (goat in a circular paddock)

We can simplify the equation for r a little. There's a simple relation between the two angles because they are in an isoceles triangle, so we can eliminate one of the cos -1 calls. Specifically, cos -1 (1 - r 2 /2) + 2cos -1 (r/2) = π Using 1 for the radius of the field, the equation for r , the tet...
by PM 2Ring
Thu Jul 21, 2016 5:45 pm UTC
Forum: General
Topic: Hifaleetin' thoughts
Replies: 90173
Views: 9105476

Re: Random natterings

Does anyone know why Kali Linux is so popular all of a sudden? [...] Kali Linux is popular with wannabe hackers. (In the break-into-systems sense, not good coders). FWIW, the vast majority of questions from Kali users on the Stack Exchange Unix & Linux site are so abysmal that they get rapidly ...
by PM 2Ring
Fri Jul 01, 2016 8:13 am UTC
Forum: General
Topic: [SAFESPACE] LGBTIQQA Thread - Queer Support!
Replies: 8248
Views: 1449913

Re: [SAFESPACE] LGBTIQQA Thread - Queer Support!

On a different topic, it strikes me that this might be a good place to ask something I was just wondering yesterday. I would like to be less hairy more often and am not really ready for big costly medical hair removal treatments or anything, but goddamn is shaving everything an enormous pain in the...
by PM 2Ring
Wed Jun 15, 2016 7:56 am UTC
Forum: Science
Topic: Relativistic Lorentz force
Replies: 38
Views: 8954

Re: Relativistic Lorentz force

It's a bit like angular momentum. There's not a completely separate 'angular momentum' from 'linear momentum', you pretty much just get angular momentum whenever linear momentum is different between two bodies; just like there's not a separate B field from the E field; and in fact the maths are som...
by PM 2Ring
Wed Jun 15, 2016 7:33 am UTC
Forum: Coding
Topic: Coding: Fleeting Thoughts
Replies: 9979
Views: 1977339

Re: Coding: Fleeting Thoughts

Incidentally, you can easily do ceiling division in Python. From http://stackoverflow.com/a/17511341/4014959

Code: Select all

def ceildiv(a, b):
    return -(-a // b)

So -a // b * -b gives the next multiple of b >= a.
by PM 2Ring
Thu Jun 09, 2016 9:46 am UTC
Forum: Individual XKCD Comic Threads
Topic: 1691: "Optimization"
Replies: 53
Views: 10439

Re: 1691: "Optimization"

According to Wikiquote there are two versions of this remark about premature optimization in Knuth's writings. Knuth calls it "Hoare's Dictum", after fellow computer scientist Tony Hoare (inventor of Quicksort, etc), but that's just Knuth having a bit of fun. The real problem is that progr...
by PM 2Ring
Wed Jun 01, 2016 4:16 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 1687: "World War III+"
Replies: 34
Views: 8187

Re: 1387: "World War III+"

@sardia

"World War III+" is actually comic #1687; comic #1387 is "Clumsy Foreshadowing".

Whatever happened to the opening post linking the thread to the comic?
by PM 2Ring
Wed Jun 01, 2016 3:58 pm UTC
Forum: General
Topic: Lucky Ten Thousand (TIL)
Replies: 13421
Views: 1718897

Re: Today I Learned

TIL: When you bleach purple hair, it turns green! I am super fascinated. I Am Not A Chemist, but I suspect that the colour change is due to a change in the oxidation state of a red pigment in the purple dye. On a (possibly) related note: In high school chemistry, I discovered that nitric acid turns...
by PM 2Ring
Mon May 30, 2016 11:29 am UTC
Forum: Individual XKCD Comic Threads
Topic: 1685 : Patch
Replies: 40
Views: 10879

Re: 1685 : Patch

A friend of mine found a python autocomplete that evaluates your code to figure out the autocomplete, so that's kind of like compiling it? I mean I know that Python can't be compiled by definition but that the same concepts, at least. Like the vast majority of modern language implementations, all i...
by PM 2Ring
Mon May 30, 2016 9:36 am UTC
Forum: Coding
Topic: Code duplication vs clarity
Replies: 15
Views: 7073

Re: Code duplication vs clarity

Since it's first and foremost a matter of whether each piece of data is included or not, I would do an alternate version of your first suggestion using binary, like this. case = 0; if (A) case &= 1; if (B) case &= 2; if (C) case &= 4; if (D) case &= 8; if (E) case &= 16; switch ...
by PM 2Ring
Tue May 17, 2016 7:36 am UTC
Forum: Language/Linguistics
Topic: Miscellaneous language questions
Replies: 590
Views: 117151

Re: Miscellaneous language questions

"Bubbler" (with 3 syllables) was the preferred term when I was in primary school, in Sydney, Australia, several decades ago. And they were generally of the unsanitary vertical stream design. In high school, we tended to call the bubblers "the taps"; "bubbler" was a term...
by PM 2Ring
Sun May 15, 2016 5:49 am UTC
Forum: Coding
Topic: Coding: Fleeting Thoughts
Replies: 9979
Views: 1977339

Re: Coding: Fleeting Thoughts

Today I discovered the horror of bug dependencies. No, not dependency bugs, those are normal. So there was a bug report for a bug. I couldn't reproduce, but the code looked like the bug should indeed occur. I digged further and discovered three related bugs, which I fixed. Now the bug from the repo...
by PM 2Ring
Fri May 13, 2016 8:53 am UTC
Forum: Individual XKCD Comic Threads
Topic: 1680: "Black Hole"
Replies: 31
Views: 7741

Re: 1680: "Black Hole"

Just how small is this black hole? Assuming that black spot is supposed to be the event horizon then it looks like it has a Schwarzschild radius of a centimetre or so. That's a rather heavy object to support with a regular coffee table. :) Maybe the coffee table and stand are made from unobtainium.....
by PM 2Ring
Thu May 12, 2016 11:46 am UTC
Forum: Science
Topic: How do we know what electron orbitals look like?
Replies: 8
Views: 3380

Re: How do we know what electron orbitals look like?

This article from 2005 by David Villeneuve Orbital Imaging: Laser-generated high-harmonic radiation produces tomographic images of molecular orbitals describes how to get the shape of the wave function of a molecular electron orbital. Using a computed tomography algorithm, we converted the data to a...
by PM 2Ring
Thu May 12, 2016 11:08 am UTC
Forum: Science
Topic: Which planet?
Replies: 28
Views: 5500

Re: Which planet?

@doogly: Love your work. I feel obliged to throw in a kind word for Mercury. Caloris Planitia is a plain within a large impact basin on Mercury, informally named Caloris, about 1,550 km (960 mi) in diameter.[1] It is one of the largest impact basins in the Solar System. The plain itself is about 685...
by PM 2Ring
Wed May 11, 2016 7:54 am UTC
Forum: Science
Topic: Alkaline Food
Replies: 26
Views: 7581

Re: Alkaline Food

Lutefisk is quite alkaline: pH of 11–12, although it is soaked in water before final preparation, which reduces the pH considerably.

Also, some people use lye as a seasoning. See viewtopic.php?t=96865&p=3211809#p3183323
by PM 2Ring
Sun May 08, 2016 11:54 am UTC
Forum: Mathematics
Topic: Seating problem
Replies: 6
Views: 2894

Re: Seating problem

Here's a Python 2 / Python 3 program that finds solutions. I haven't looked at Flumble's code, but I am using lorb's optimization. My approach is to express the problem as an Exact Cover problem. Our goal is to find sets of 4 permutations so that each of the 10 people get exactly 8 neighbours over t...
by PM 2Ring
Sun May 08, 2016 8:34 am UTC
Forum: Coding
Topic: [Resolved] Generalized Hamming numbers in Python
Replies: 3
Views: 4303

Re: Generalized Hamming numbers in Python

What Xanthir said, although you really only need to worry about m . Here's my version. It creates the generator expressions using a function multiples that takes i and m as args. It would work if you only pass m as an arg, but I think it improves readability to pass them both. My code doesn't use yi...
by PM 2Ring
Sat May 07, 2016 10:59 am UTC
Forum: Coding
Topic: Coding: Fleeting Thoughts
Replies: 9979
Views: 1977339

Re: Coding: Fleeting Thoughts

I'm actually going to rewrite in C++ for the performance gains. The full program may take days to run in python. Wise. I love Python, but it's not particularly fast or conservative of RAM. FWIW, in 32 bit CPython a small Python integer (i.e., one that fits into a 32 bit signed machine integer) cons...
by PM 2Ring
Fri May 06, 2016 8:08 am UTC
Forum: Fictional Science
Topic: Fiction Idea: Breaking out of the simulation
Replies: 12
Views: 9734

Re: Fiction Idea: Breaking out of the simulation

Copper Bezel wrote:
Spoiler:
Including the matryoshka doll zinger at the end. Of course, you get that with The Thirteenth Floor and Inception and all of these things, it's basically obligatory....

Spoiler:
It's turtles virtuals all the way down.
by PM 2Ring
Fri May 06, 2016 8:00 am UTC
Forum: Individual XKCD Comic Threads
Topic: 1676: "Full-Width Justification"
Replies: 64
Views: 18513

Re: 1676: "Full-Width Justification"

YMMV, but personally I admire the documentation for FFTW , clearly written by people who have a mastery not only of their topic but of the English language too. It's direct without being overly informal, and has jokes and humorous footnotes that enhance readability without detracting from the clari...
by PM 2Ring
Thu May 05, 2016 8:16 am UTC
Forum: Individual XKCD Comic Threads
Topic: 1676: "Full-Width Justification"
Replies: 64
Views: 18513

Re: 1676: "Full-Width Justification"

My Linotype keyboarding manual talks quite a bit about justification. On a Linotype, automatic justification was achieved by adjusting the space between words with variable width spaces that would evenly divide up the space when the line was sent to cast. [...] ETAOIN SHRDLU Many years ago, I was g...
by PM 2Ring
Thu May 05, 2016 7:39 am UTC
Forum: Science
Topic: Dropping a Cloud Nine From Orbit
Replies: 38
Views: 7188

Re: Dropping a Cloud Nine From Orbit

Maybe I'm missing something here, but I don't see what the big problem is with just constructing the dome on the ground. Of course, it's not going to support its own weight when it's partly built, but why does it need to do that? It's a tensegrity structure, so you just build it flat, with plenty of...
by PM 2Ring
Tue May 03, 2016 7:41 am UTC
Forum: Language/Linguistics
Topic: Miscellaneous language questions
Replies: 590
Views: 117151

Re: Miscellaneous language questions

Spoiler:
Image
by PM 2Ring
Thu Apr 21, 2016 12:33 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 1670: "Laws of Physics"
Replies: 46
Views: 12352

Re: 1670: "Laws of Physics"

AFAIK, Feynman did it first. "There were 183 of us freshmen, and a bowling ball hanging from the three-story ceiling to just above the floor. Feynman walked in and, without a word, grabbed the ball and backed against the wall with the ball touching his nose. He let go, and the ball swung slowly...
by PM 2Ring
Tue Apr 19, 2016 8:23 am UTC
Forum: General
Topic: Lucky Ten Thousand (TIL)
Replies: 13421
Views: 1718897

Re: Today I Learned

Nice round-cut diamond. Do you have Princess and Cushion cuts too? Thanks! No, I only have variations on the Tolkowsky brilliant cut. There's an old POV-Ray include file for a brilliant cut, but I wasn't happy with it, so I made an improved version by referring to Tolkowsky's book: A Study of the R...
by PM 2Ring
Mon Apr 18, 2016 8:28 am UTC
Forum: General
Topic: Lucky Ten Thousand (TIL)
Replies: 13421
Views: 1718897

Re: Today I Learned

... and that the LEDs on the webcam are bright enough to cause positive phototropism: http://i300.photobucket.com/albums/nn9/Sableagle/Demolition%20Ranch%20Barrett/apple_seedlings_zpsey0x1zye.gif Now trying again with a different species, from a higher angle. Interesting! I was going to ask you why...
by PM 2Ring
Mon Apr 18, 2016 8:06 am UTC
Forum: General
Topic: Origami and Mental Illness
Replies: 7
Views: 4578

Re: Origami and Mental Illness

Impressive work, Cleverbeans! FWIW, I've folded quite a few flapping birds over the decades, but never any that tiny. (But I do have a cellophane one on my desk that I folded about 20 years ago).
by PM 2Ring
Mon Apr 18, 2016 7:57 am UTC
Forum: Coding
Topic: Coding: Fleeting Thoughts
Replies: 9979
Views: 1977339

Re: Coding: Fleeting Thoughts

Everyone knows the feeling when something that should work, doesn't. Today I got to experience the more rare feeling of something working, which shouldn't. I get uncomfortable when that happens, and if I can't prove to myself why it behaves the way it does I have to change it to something I do unde...
by PM 2Ring
Mon Apr 18, 2016 7:38 am UTC
Forum: Individual XKCD Comic Threads
Topic: 1668: "Singularity"
Replies: 26
Views: 7802

Re: 1668: "Singularity"

And for those who don't know who keithl is, please see Keith Lofstrom , Launch loop , and Keith Lofstrom's Vanity Web Page . wait. wait. ...uhh... ..uh..ok..Tell me. Is our Keith That Keith? ...Well,...ok. ... I'm willing to believe it... We are in the company of some very fine minds. He sure is. F...
by PM 2Ring
Sat Apr 16, 2016 7:31 am UTC
Forum: Individual XKCD Comic Threads
Topic: 1666: "Brain Upload"
Replies: 38
Views: 8520

Re: 1666: "Brain Upload"

So as far as I know, we haven't covered the initial So in this forum (no doubt it's been discussed elsewhere on the board, but...). I quite like it, actually; or at least it doesn't annoy me. It seems to me that so is used in the sense "what I'm about to say follows directly from your question...
by PM 2Ring
Sat Apr 16, 2016 7:07 am UTC
Forum: Individual XKCD Comic Threads
Topic: 1668: "Singularity"
Replies: 26
Views: 7802

Re: 1668: "Singularity"

Keyman wrote:So does the "l" in 'keithl' stand for Leibowitz?


Good call. :) For those who don't get the reference, please see A Canticle for Leibowitz.

And for those who don't know who keithl is, please see Keith Lofstrom, Launch loop, and Keith Lofstrom's Vanity Web Page.
by PM 2Ring
Mon Apr 11, 2016 6:35 am UTC
Forum: Mathematics
Topic: Simplifying expressions with unit'd values
Replies: 13
Views: 3508

Re: Simplifying expressions with unit'd values

What is the meaning of units in the denominator in this case? Can you provide an example of how this would be used and what it would translate to physically? We need ratios of lengths if we want to be able to scale things and ensure the scaled version is a similar shape ( in the sense of similar tr...
by PM 2Ring
Sat Apr 09, 2016 8:40 am UTC
Forum: Mathematics
Topic: Efficient Prizims
Replies: 9
Views: 2478

Re: Efficient Prizims

As gmalivuk said, this is easy to do if you know some calculus, but it's not too hard to verify that s=4 gives the maximum volume for the open box. To make the arithmetic simpler, I'll scale the square down by ¼, so that s=1 and the original square is 6 x 6. The base of the box has length and width ...
by PM 2Ring
Tue Mar 29, 2016 12:40 am UTC
Forum: Coding
Topic: Coding: Fleeting Thoughts
Replies: 9979
Views: 1977339

Re: Coding: Fleeting Thoughts

So there's this idea I have about tying chats/media shares like telegram, IRC and WhatsApp (using yowsup) together, but I'm unsure as to what common backend to use. The goal is to have all messages available to any networked device, though preferably messages would be loaded on demand, like a typic...
by PM 2Ring
Fri Mar 11, 2016 6:25 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 1654: "Universal Install Script"
Replies: 57
Views: 21854

Re: 1654: "Universal Install Script"

INB4 : Hey this only works if you have a *nix shell running in the first place! Anyone else here old enough to have thought the pip install was referring to this? Anyway, "install" is where horses should be. I'm old enough to have used pip on CP/M, and I was certainly reminded of that pip...

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