Search found 1752 matches

by Token
Fri Jun 22, 2012 7:52 am UTC
Forum: Individual XKCD Comic Threads
Topic: 1072: " Seventies"
Replies: 117
Views: 27384

Re: 1072: " Seventies"

Better fix the alt-text. The "this" is using a contemporary 's'. There was in fact a period where the modern shape (short s) was used at the end of words in print but the long s was used at the beginning or in the middle, so this is not incorrect (though I haven't actually verified that t...
by Token
Mon May 21, 2012 10:11 pm UTC
Forum: Coding
Topic: Was I too harsh?
Replies: 167
Views: 41674

Re: Was I too harsh?

Is it a Senior Software Engineer position for Lochheed Martin where you're writing programs that UAVs rely on (ie, people die if the code is wrong)? The U really helps though, when it comes to safety Not when you're dropping bombs from the things... That would be a case of people dying if the code ...
by Token
Sat May 12, 2012 11:14 am UTC
Forum: Coding
Topic: Regular expressions, HTML and turning breaks into paragraphs
Replies: 4
Views: 3462

Re: Regular expressions, HTML and turning breaks into paragr

Regular expressions are a powerful tool, but to use them properly you need to have a good understanding of both their strengths and their limitations. It's well known that they are not capable of parsing arbitrary HTML (the "regular" in "regular expression" has a technical meanin...
by Token
Fri Apr 27, 2012 6:29 am UTC
Forum: Mathematics
Topic: Triangulation of a torus
Replies: 4
Views: 3556

Re: Triangulation of a torus

Exactly right. Check out the definition of a triangulation - it's a homeomorphism between a simplicial complex and whatever space you're triangulating. A simplicial complex is just a glued-together collection of simplices, which are just triangles / tetrahedrons / higher-dimesional versions of the s...
by Token
Sat Apr 21, 2012 10:49 am UTC
Forum: Mathematics
Topic: Question about Cauchy Sequences
Replies: 7
Views: 2201

Re: Question about Cauchy Sequences

Ah, of course - if you make sure that you always have nk < mk < nk+1, you can start at n1 and inductively from nk either go straight to nk+1 or go via mk. I was trying to make the triangle inequality work for me, but didn't think of applying pigeonhole >.<
by Token
Fri Apr 20, 2012 7:15 pm UTC
Forum: Mathematics
Topic: Question about Cauchy Sequences
Replies: 7
Views: 2201

Re: Question about Cauchy Sequences

Then we can find some ε > 0 and an increasing sequence {n k } such that d(f(x n_k ), f(x n_{k+1} )) > ε for all k. Is this obvious? I'm prone to missing simple things at the best of times and I've not done any proper maths in a while, so bear with me. I know that directly from the definition of not...
by Token
Thu Jan 26, 2012 1:00 am UTC
Forum: Mathematics
Topic: Set-theoretic brain fart
Replies: 9
Views: 2057

Re: Set-theoretic brain fart

In my amateur opinion, I don't think the "large" in "large cardinal" means what you think it means. I mean, you already know that size is relative, so in some sense it can't. Besides, in any model of ZFC, the cardinals already go all the way up to the top. I don't see that adding...
by Token
Sat Nov 12, 2011 12:04 am UTC
Forum: Coding
Topic: Database structure problem with tags, categories
Replies: 19
Views: 4297

Re: Database structure problem with tags, categories

Yeah, having a "tags" column in the "media" table is going to make querying a bitch, not to mention that it's poor relational design. Your best option is to have a separate table with a "media_id" column FKed to the "media" table, and a "type" (or &q...
by Token
Sat Aug 06, 2011 11:30 pm UTC
Forum: Coding
Topic: O(you make baby Jesus cry)
Replies: 19
Views: 4408

Re: O(you make baby Jesus cry)

Is this what you're trying to work out, whether or not these elements are always built up by commutators? Its certainly the elegant hypothesis, but imo it'd be wildly more interesting if there are solutions that didn't look like that for some n. Well, even for the 3-element case, you have solutions...
by Token
Wed Jun 08, 2011 2:38 pm UTC
Forum: Mathematics
Topic: Math is a language, not a science?
Replies: 87
Views: 22901

Re: Math is a language, not a science?

You have proved the existence of an inconsistent statement though non-constructive means. Why do you seem to think knowing something exists means we can explicitly construct it? There are hundreds of existence proofs that don't explicitly construct the object you show to exist. But there is a conce...
by Token
Wed Jun 08, 2011 2:31 pm UTC
Forum: Mathematics
Topic: Arbitrarily large groups with no non-trivial subgroups?
Replies: 5
Views: 1136

Re: Arbitrarily large groups with no non-trivial subgroups?

The only groups with no non-trivial proper subgroups are the cyclic groups of prime order.
by Token
Tue Jun 07, 2011 9:17 pm UTC
Forum: Mathematics
Topic: Math is a language, not a science?
Replies: 87
Views: 22901

Re: Math is a language, not a science?

Does it matter? You were told by a reliable source. You designed a quantum computer that searches through every derivation simultaneously and stops when it reaches a contradiction, but due to hardware limitations is unable to tell you what the problematic derivation was. Whatever. Sigh. Why not jus...
by Token
Tue Jun 07, 2011 4:22 pm UTC
Forum: Mathematics
Topic: Math is a language, not a science?
Replies: 87
Views: 22901

Re: Math is a language, not a science?

But if you can't find out what the paradox is without actually running the proof that leads to it, then of course running that proof tells you something useful. My point being, if you don't know what the paradox is or how to derive it, how do you know that there's a paradox? Or, to rephrase, if you...
by Token
Tue Jun 07, 2011 9:40 am UTC
Forum: Mathematics
Topic: Math is a language, not a science?
Replies: 87
Views: 22901

Re: Math is a language, not a science?

If Bertrand Russell bothers to tell you what the paradox is, proving P from it tells you nothing useful. Unless you're saying it's possible to deduce the inconsistency of Y without also having enough information to derive a contradiction from its axioms?
by Token
Mon Jun 06, 2011 11:13 pm UTC
Forum: Logic Puzzles
Topic: A [Joint] Effort
Replies: 18
Views: 2886

Re: A [Joint] Effort

I'm betting those words are going to be relevant later (along with "joint" and "subject").
by Token
Mon Jun 06, 2011 10:39 pm UTC
Forum: Mathematics
Topic: Math is a language, not a science?
Replies: 87
Views: 22901

Re: Math is a language, not a science?

Find me a definition of "proven" from a reputable source that doesn't require truth. If "P" and "not P" are both shown to follow from the axioms of a system, neither can be true (as it being so would contradict the truth-iness of the other one which has just as much ri...
by Token
Sat Jun 04, 2011 7:47 pm UTC
Forum: Mathematics
Topic: Math is a language, not a science?
Replies: 87
Views: 22901

Re: Math is a language, not a science?

Ah, I see. What you actually mean is that they reject unrestricted comprehension. I think I mostly agree with you, then.
by Token
Sat Jun 04, 2011 6:45 pm UTC
Forum: Mathematics
Topic: Math is a language, not a science?
Replies: 87
Views: 22901

Re: Math is a language, not a science?

Fine, if you want to think of ZFC as a purely syntactic thing, go ahead. I think of it as both a semantic and a syntactic object, which happen to coincide, so that e.g. the axiom of extensionality says, "Sets are determined by membership," rather than, "∀A∀B (∀C(C ϵ A <->C ϵ B) -> A ...
by Token
Sat Jun 04, 2011 2:52 pm UTC
Forum: Mathematics
Topic: Math is a language, not a science?
Replies: 87
Views: 22901

Re: Math is a language, not a science?

When we say "let S = {f : f is continuous and has compact support}" we really are using the comprehension axiom; when we prove A subset B and B subset A and conclude A=B we're using extensionality; and so forth, even if we're not consciously thinking in those terms. Not at all. If I move ...
by Token
Sat Jun 04, 2011 12:40 pm UTC
Forum: Mathematics
Topic: Math is a language, not a science?
Replies: 87
Views: 22901

Re: Math is a language, not a science?

Well, the only difference between naive set theory and ZFC is that the axiom of unrestricted comprehension is replaced by restricted comprehension, so I don't think this is true. People think in terms of naive set theory, but (those who are aware of the paradoxes) restrict their uses of comprehensi...
by Token
Fri Jun 03, 2011 7:19 pm UTC
Forum: Mathematics
Topic: Nerd-Sniped with "Simple" Equation.
Replies: 9
Views: 2613

Re: Nerd-Sniped with "Simple" Equation.

1) Find the minimal polynomial that has \sqrt{2}+\sqrt{3} as a root. 2) Find the minimal polynomial that has \sqrt{2}+\sqrt{3}+\sqrt{5} as a root. 3) Find the minimal polynomial that has \sqrt{2}+\sqrt[3]{2} as a root. I got sniped so hard... 1) x^4 - 10x^2 + 1 2) x^8 - 40x^6 + 352x^4 - 960...
by Token
Thu Jun 02, 2011 2:26 pm UTC
Forum: Mathematics
Topic: Too easy of an undergrad?
Replies: 20
Views: 2943

Re: Too easy of an undergrad?

Should you be able to answer the question? I'd guess not - I don't know exactly how your class system works, but it's a level of linear algebra that's above what I'd call "basic". I'm surprised you don't know what an isomorphism is, though...
by Token
Thu Jun 02, 2011 10:17 am UTC
Forum: Mathematics
Topic: Proof that there are at least 5 regular polyhedra?
Replies: 11
Views: 2880

Re: Proof that there are at least 5 regular polyhedra?

So, the OP asks if there's a proof beside exhibiting the examples, and you tell him there's no need to have one because he can just exhibit the examples? I'm getting the feeling that you've missed the point somewhere...
by Token
Tue May 31, 2011 3:55 pm UTC
Forum: Mathematics
Topic: A criminal hides in a room with 99 innocent people...
Replies: 13
Views: 4190

Re: A criminal hides in a room with 99 innocent people...

There's one thing I'm left wondering. Is there an intuitive explanation for the fact that the conditional probability that the criminal appears guilty given 5 positive tests exactly coincides with the prior probability without knowing the number of positive tests? If you apply Bayes' theorem, you'l...
by Token
Mon May 16, 2011 2:02 pm UTC
Forum: Mathematics
Topic: Uncountably Many Zeroes
Replies: 38
Views: 3831

Re: Uncountably Many Zeroes

Any closed set is the zero-set of a continuous function - namely, the function that takes a point and returns the distance from that point to the set. And the Cantor set is closed and uncountable :)
by Token
Thu Mar 03, 2011 5:58 pm UTC
Forum: Mathematics
Topic: Infinite sets, again
Replies: 6
Views: 829

Re: Infinite sets, again

There's a fairly easy-to-understand injection from R to NN - given an arbitrary real, have the first number represent the sign, the second be the integer part, and the rest be the decimal expansion of the fractional part.
by Token
Sun Feb 27, 2011 6:40 pm UTC
Forum: Coding
Topic: Catch question
Replies: 5
Views: 1214

Re: Catch question

Area Man wrote:Exception handling is for run-time errors, not syntax or compiler errors - OP seems a bit confused there.

I think the OP is referring to IDEs with debug modes and some kind of break-on-exception thing - which are fairly common.
by Token
Sun Feb 27, 2011 4:14 pm UTC
Forum: Science
Topic: If modern weapons didn't exist, what would combat look like?
Replies: 95
Views: 6464

Re: If modern weapons didn't exist, what would combat look l

Doesn't naval warfare predate gunpowder anyway?
by Token
Tue Feb 15, 2011 8:50 pm UTC
Forum: Mathematics
Topic: "nontrivial subgroups" (terminology question)
Replies: 7
Views: 2088

Re: "nontrivial subgroups" (terminology question)

The trivial subgroup of any group G is the subgroup with just one element. You say that like maths terminology is standardised. I seem to recall (though I may easily be wrong) that one of my group theory lecturers for my master's explicitly enumerated the trivial subgroup s of a group G as {e} and ...
by Token
Tue Feb 15, 2011 8:37 pm UTC
Forum: Mathematics
Topic: Is this a meaningless math question?
Replies: 24
Views: 2558

Re: Is this a meaningless math question?

It *is* a meaningless question - or at least, it's a poorly defined one. What do you mean by "choose randomly"? There are many possibilities, and the intuitive one (choosing uniformly at random) isn't possible.
by Token
Mon Feb 14, 2011 8:01 pm UTC
Forum: Logic Puzzles
Topic: Cut this in half.
Replies: 10
Views: 2628

Re: Cut this in half.

I recall from somewhere that two dimensions requires (in general) countably infinitely many cuts...
by Token
Mon Feb 14, 2011 7:53 pm UTC
Forum: Logic Puzzles
Topic: Sums Puzzle
Replies: 4
Views: 1407

Re: Sums Puzzle

I'm convinced I've misunderstood something or made a mistake somewhere... WLOG the numbers are all non-negative, and the smallest is zero (since the game is unchanged by adding a constant to each number). Whatever numbers B erases, the remainder must sum to a multiple of n-1. It follows that...
by Token
Wed Feb 09, 2011 7:12 pm UTC
Forum: Gaming
Topic: Wikirace (And other Wikipedia / Search Engine Games)
Replies: 11
Views: 2900

Re: Wikirace (And other Wikipedia / Search Engine Games)

But there was one in 2008.
by Token
Sun Jan 30, 2011 2:32 am UTC
Forum: Coding
Topic: N00b question in Javascript
Replies: 9
Views: 1712

Re: N00b question in Javascript

Heylo guys, I have a rather noob question in Javascript. How can i reduce the code and make it more portable/expandable? newpage.document.form4.english.value=newpage.document.form4.english.value.replace(/<startdate>/g, startdate); newpage.document.form4.english.value=newpage.document.form4.english....
by Token
Tue Jan 18, 2011 2:27 am UTC
Forum: Coding
Topic: How do i clear the input buffer in C?
Replies: 4
Views: 2899

Re: How do i clear the input buffer in C?

In my opinion at least, it is bad practice to read from stdin using scanf. scanf is best used when you have a reasonable assumption as to the format of your input. Unfortunately, user input can be pretty much anything. Even with Zabaron's suggestion, say, a user entering "1 2 3 4 5" will h...
by Token
Mon Jan 17, 2011 6:23 pm UTC
Forum: Mathematics
Topic: Solve 2^x = x^2 without using "By Observation"
Replies: 21
Views: 34217

Re: Solve 2^x = x^2 without using "By Observation"

Transliterated Greek. "Ascending" and "descending".
by Token
Sun Jan 09, 2011 2:52 pm UTC
Forum: Coding
Topic: [C++] Numeric data validation
Replies: 16
Views: 2945

Re: [C++] Numeric data validation

1.- About using exceptions, can I do something like this -without using strings-? It's not working. int A; cout << "Enter a number.\n"; try{ cin >> A; } catch (...) { cout << "The number has to be an integer."; } That won't work because by default, exception throwing for istream...
by Token
Wed Dec 29, 2010 12:24 am UTC
Forum: Coding
Topic: [FIXED]ClassNotFoundException on any Java program in Eclipse
Replies: 12
Views: 3667

Re: ClassNotFoundException on any Java program in Eclipse

Have you tried doing a full clean and build?
by Token
Wed Dec 22, 2010 12:03 pm UTC
Forum: Gaming
Topic: EVE Online
Replies: 4827
Views: 593038

Re: EVE Online

Scamming is inconsistent, but good isk. Other than that, everything mentioned. Buy low/sell high works between market hubs, with sufficient volume. Helps to have an army of freighter alts, of course. You don't need that much volume. A single trade alt with a transport ship was enough to make me any...
by Token
Tue Nov 30, 2010 4:43 pm UTC
Forum: Coding
Topic: Java Generics and Defining Type Bounds
Replies: 6
Views: 1769

Re: Java Generics and Defining Type Bounds

So the question becomes - why do you *need* it to be possible? There may well be a more sensible way of doing what you're trying to do...

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