Search found 213 matches

by Demki
Mon May 07, 2018 5:56 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 1990: "Driving Cars"
Replies: 86
Views: 9084

Re: 1990: "Driving Cars"

Here you have to take at least 28 lessons, along with a theoretical exam, before you are allowed to test for a driving license.

Doesn't stop people from driving badly.
by Demki
Wed Apr 25, 2018 6:59 am UTC
Forum: Computer Science
Topic: Desirable Coding Skills
Replies: 13
Views: 1891

Re: Desirable Coding Skills

In addition to the video series xanthir recommended (which I also recommend, 3Blue1Brown is really good in general), I also recommend paul's math notes , a site that contains a lot of fairly in-depth explanations and examples for calculus(I believe there's there algebra too). iirc it also has proble...
by Demki
Sat Mar 24, 2018 4:49 pm UTC
Forum: Coding
Topic: What language should I learn?
Replies: 15
Views: 4806

Re: What language should I learn?

Lately, I've been using Haskell quite a lot for solving Project Euler problems. Usually I'm done in a couple of lines (and hours of thinking, fiddling with expressions and debugging –debugging edge cases, mind you, there's no debugging of null pointers or anything) and the runner is done in a coupl...
by Demki
Fri Feb 23, 2018 11:24 am UTC
Forum: Mathematics
Topic: Prove that dim Spec A = dim Spec A/p + dim Spec A_p
Replies: 2
Views: 1517

Re: Prove that dim Spec A = dim Spec A/p + dim Spec A_p

doogly wrote:This stinks like something with a two line proof using categories.

Obligatory reference
by Demki
Wed Feb 07, 2018 7:01 pm UTC
Forum: Coding
Topic: Coding: Fleeting Thoughts
Replies: 9862
Views: 1764721

Re: Coding: Fleeting Thoughts

Assuming this is the global object( window or global ): (function() { function factorial(n) { // or any function such that f(0)=f(1) and f(2)/=f(3) let res = 1; for(let i = 2; i <= n; ++i) res *= i; return res; } let something = 4; Object.defineProperty(this, 'a', { get() { let res = factorial(somet...
by Demki
Thu Dec 14, 2017 4:16 pm UTC
Forum: Mathematics
Topic: Bump Function
Replies: 7
Views: 3138

Re: Analytic Bump Function

This may or may not be useful: by simply taking the derivative, we get that f'(x) = f(x) * g 1 (x) (for some g 1 ) therefore f''(x) = f'(x) * g 1 (x) + f(x) * g 1 '(x) = f(x) * (g 1 (x))^(2) + f(x) * g 1 '(x) = f(x) * g 2 (x) (for some g 2 ) This can be extended to f (n) (x) = f(x) * g n (x)...
by Demki
Thu Oct 05, 2017 12:44 pm UTC
Forum: Mathematics
Topic: What is linear algebra?
Replies: 3
Views: 2202

Re: What is linear algebra?

Linear algebra is less about "lines and their equals" and more about vector spaces, and linear functions between them. Linear functions are functions that preserve vector addition and multiplication by a scalar. In linear algebra you'll learn what a vector space is, and you'll learn about ...
by Demki
Mon Sep 18, 2017 9:52 pm UTC
Forum: Coding
Topic: Manufactoria - Make Turing Machines with Conveyor Belts
Replies: 350
Views: 93301

Re: Manufactoria - Make Turing Machines with Conveyor Belts

Looks cool from the video, and it has a demo so I can check it out when I get home! Excellent, let me know how it goes! Nice interface, although I could've gone with a smaller font size. I like that you added keybinding for the different modules, however I would like the ability to rebind keys(for ...
by Demki
Mon Sep 18, 2017 5:04 pm UTC
Forum: Coding
Topic: Manufactoria - Make Turing Machines with Conveyor Belts
Replies: 350
Views: 93301

Re: Manufactoria - Make Turing Machines with Conveyor Belts

I'm going to be incredibly rude and necro this 7-year-old thread to post some news: I've made a new game! It's called Silicon Zeroes, it's a spiritual sequel to Manufactoria, and it's out right now on Steam and itch.io. Just a heads-up :) Looks cool from the video, and it has a demo so I can check ...
by Demki
Tue Sep 12, 2017 10:21 pm UTC
Forum: Logic Puzzles
Topic: 538 hats riddle
Replies: 20
Views: 4555

Re: 538 hats riddle

That solution reminds me of another riddle, where each of n participants is given a hat with a random color out one of n different colors(and what color one person gets is independent of what the rest get) and they need to form a strategy such that at least one of them must guess their own color cor...
by Demki
Tue Sep 12, 2017 5:06 am UTC
Forum: Coding
Topic: Coding: Fleeting Thoughts
Replies: 9862
Views: 1764721

Re: Coding: Fleeting Thoughts

Indeed it appears that none of Internet Explorer, Edge, and IE Mobile support the 'tab-size' CSS property, at least according to MDN's documentation.
I guess Microsoft really want you to use a very specific tab-size, or else...
by Demki
Tue Aug 08, 2017 10:42 pm UTC
Forum: Coding
Topic: var == 'value' vs 'value' == var
Replies: 20
Views: 8645

Re: var == 'value' vs 'value' == var

Yeah, that's a reasonable retort. Anyone who does "foo() == true" is making a mistake in the first place. ^_^ I've seen that used in C# where foo() returns (bool?) as shorthand for: bool? x = foo(); if(x != null && x.Value) // ... or bool? x = foo(); if(x.HasValue && x.Val...
by Demki
Sat Jul 15, 2017 9:19 pm UTC
Forum: Logic Puzzles
Topic: New kind of puzzle
Replies: 17
Views: 4256

Re: New kind of puzzle

I can do it for you if it just come to the colors inside the circles (It will take me 30 minutes) but how could I replace the links (in yellow) between circles? After rethinking I believe that it will hard to guess the rules. So if no one find the rules (which is part of the puzzle) then I will pos...
by Demki
Sat Jul 15, 2017 8:41 pm UTC
Forum: Logic Puzzles
Topic: New kind of puzzle
Replies: 17
Views: 4256

Re: New kind of puzzle

Looks interesting, but I'm having trouble with the colors(I have color-vision deficiency), do you have a version where the colors are replaced by numbers/letters?
by Demki
Thu Jun 29, 2017 11:13 am UTC
Forum: Religious Wars
Topic: Spaces in paths & filenames
Replies: 45
Views: 9547

Re: Spaces in paths & filenames

Does DOS/Windows allow single quotes at all? I seem to remember it only liking double quotes, and wine cmd says "File not found" when I try to use single quotes with dir and type. Testing on a windows 10 machine: cmd.exe doesn't accept 'single quotes', only "double quotes". powe...
by Demki
Sun Jun 25, 2017 3:52 am UTC
Forum: Religious Wars
Topic: Spaces in paths & filenames
Replies: 45
Views: 9547

Re: Spaces in paths & filenames

Funnily enough, Powershell handles tab-completion with files that have spaces in them just fine, it even automatically wraps the path in double quotes for you. Powetshell is far from perfect, but at least you can easily type /pro[tab, perhaps more than once] to get "C:\Program Files (x86)\"...
by Demki
Wed Jun 14, 2017 5:01 am UTC
Forum: Mathematics
Topic: What would happen if $-1 bills were minted?
Replies: 20
Views: 5502

Re: What would happen if $-1 bills were minted?

Something like that exists here in Norway [...]A giro: I buy something from you, you write a giro and give it to me. I hand in the giro to my bank, and the money moves from my bank to yours. What if you don't hand the giro to the bank? Jose I'd assume it'd result in either a lawsuit, or in the loss...
by Demki
Tue Jun 06, 2017 8:10 pm UTC
Forum: Logic Puzzles
Topic: Guess the Pattern
Replies: 21
Views: 5948

Re: Guess the Pattern

Keeping a list of my observations so far. ⋅  All shown outputs are prime or X ⋅  All shown outputs, where they are not X, are coprime to the inputs. ⋅  All integers of the form 6n+1 shown, except for 1, result in X ⋅  All other shown integers that result in X ...
by Demki
Thu May 25, 2017 2:11 pm UTC
Forum: Mathematics
Topic: How to learn about radical expressions and equations ?
Replies: 12
Views: 3159

Re: How to learn about rational expressions and equations ?

A bit more information about your current mathematical education would be helpful for us to guide you in the correct direction.
by Demki
Tue May 23, 2017 11:37 am UTC
Forum: Coding
Topic: Coding: Fleeting Thoughts
Replies: 9862
Views: 1764721

Re: Coding: Fleeting Thoughts

Even better. As you guessed, Javascript will automatically add a semicolon at the end of a line if it makes syntactic sense. But then the brace becomes the start of a block statement, not the start of an object literal. Inside that block is the (useless) label "foo", on the (pointless) st...
by Demki
Tue May 23, 2017 9:55 am UTC
Forum: Coding
Topic: Coding: Fleeting Thoughts
Replies: 9862
Views: 1764721

Re: Coding: Fleeting Thoughts

I don't know much javascript but I am guessing line breaks act as statement separators(like semicolon), so the first one acts like return; essentially returning nothing, while the second one has an opening brace so it returns everything until the closing brace. I am guessing that's because javascrip...
by Demki
Sat May 06, 2017 10:11 pm UTC
Forum: Mathematics
Topic: Mathematical Induction - Introductory Question
Replies: 257
Views: 30710

Re: Mathematical Induction - Introductory Question

Yes, basically. What you want is simply to derive the (n=k+1) case given the (n=k) case, as has been done in the proof you've given, along with a base case.
by Demki
Sat May 06, 2017 10:04 pm UTC
Forum: Mathematics
Topic: Mathematical Induction - Introductory Question
Replies: 257
Views: 30710

Re: Mathematical Induction - Introductory Question

It's not, it is just missing a base case.
by Demki
Wed May 03, 2017 4:42 pm UTC
Forum: Mathematics
Topic: Mathematical Induction - Introductory Question
Replies: 257
Views: 30710

Re: Mathematical Induction - Introductory Question

The even/odd definition I posted apply for all integers, not just the positive ones. 0 is a multiple of 2(2*0=0), therefore it is even. 0 is divisible by every number except 0.
by Demki
Wed May 03, 2017 4:36 pm UTC
Forum: Mathematics
Topic: Mathematical Induction - Introductory Question
Replies: 257
Views: 30710

Re: Mathematical Induction - Introductory Question

Yes! That is a valid argument, and a perfect example of proof by induction. You have the base step, the induction step, and you correctly justify your conclusion using known properties of even and odd numbers. But my argument still contains an assumption that I'd need to build out (I think), which ...
by Demki
Wed May 03, 2017 3:57 pm UTC
Forum: Mathematics
Topic: Mathematical Induction - Introductory Question
Replies: 257
Views: 30710

Re: Mathematical Induction - Introductory Question

The first sentence you wrote just reiterates the definition of an even number. You gave no justification for why every integer that isn't even to be odd, since odd means 1 greater than an even number. The proof by induction provides such justification. I have to start somewhere. By necessity, becau...
by Demki
Wed May 03, 2017 3:28 pm UTC
Forum: Mathematics
Topic: Mathematical Induction - Introductory Question
Replies: 257
Views: 30710

Re: Mathematical Induction - Introductory Question

The first sentence you wrote just reiterates the definition of an even number. You gave no justification for why every integer that isn't even to be odd, since odd means 1 greater than an even number. The proof by induction provides such justification.
by Demki
Wed May 03, 2017 3:09 pm UTC
Forum: Mathematics
Topic: Mathematical Induction - Introductory Question
Replies: 257
Views: 30710

Re: Mathematical Induction - Introductory Question

What background knowledge? Do you have some other proof that every integer is either even or odd? Remember that "n is even" means "there exists m such that n=2m" and "n is odd" means "there exists m such that n=2m+1" Did you ever prove the statement "ever...
by Demki
Wed May 03, 2017 2:55 pm UTC
Forum: Mathematics
Topic: Mathematical Induction - Introductory Question
Replies: 257
Views: 30710

Re: Mathematical Induction - Introductory Question

:arrow: It's pedagogically useful. It is nice to practice proof by induction if you do not understand induction by using it to prove things which you can already understand and prove by another means. I would agree with that, but the problem with the even-odd example is that it doesn't (at least in ...
by Demki
Wed May 03, 2017 2:42 pm UTC
Forum: Mathematics
Topic: Mathematical Induction - Introductory Question
Replies: 257
Views: 30710

Re: Mathematical Induction - Introductory Question

Proof by induction is usually useful when you want to prove some statement about all integers greater than or equal to some starting value. The original problem in this thread has the statement "1+2+3+...+(n-1)+n=n(n+1)/2" The even-odd problem has the statement "n is even or n is odd&...
by Demki
Wed May 03, 2017 2:25 pm UTC
Forum: Mathematics
Topic: Mathematical Induction - Introductory Question
Replies: 257
Views: 30710

Re: Mathematical Induction - Introductory Question

Fun fact: the top answer to the question "how to prove that every integer is either even or odd" on math stackexchange is proof by induction.
https://math.stackexchange.com/question ... ven-or-odd
by Demki
Wed May 03, 2017 5:21 am UTC
Forum: Mathematics
Topic: Mathematical Induction - Introductory Question
Replies: 257
Views: 30710

Re: Mathematical Induction - Introductory Question

I'll just leave this here. It's the post I posted a page ago and was completely ignore by mathdofus. I ask that you read this post, if you hit a point you don't understand, write down what you don't understand on a piece of paper and continue reading, writing the points you don't understand. Then re...
by Demki
Wed May 03, 2017 4:17 am UTC
Forum: Coding
Topic: Basic Question Involving Functions (Python)
Replies: 18
Views: 7302

Re: Basic Question Involving Functions (Python)

The tutorials and books Xanthir linked are aimed at people who have no programming backgroud, so they should teach you, along with the specifics of the python language, how programming works. I didn't check them all but they probably include example problems and solutions(using python). Once you hav...
by Demki
Tue May 02, 2017 9:49 pm UTC
Forum: Mathematics
Topic: Mathematical Induction - Introductory Question
Replies: 257
Views: 30710

Re: Mathematical Induction - Introductory Question

But you don't seem to know how to prove them, which is what we're doing here. We keep circling around this same problem. The induction step is just a conditional proof. If I demonstrate that a base case is true, and then demonstrate that if the k case is true then the (k + 1) case is true, then I'v...
by Demki
Tue May 02, 2017 9:00 pm UTC
Forum: Mathematics
Topic: Mathematical Induction - Introductory Question
Replies: 257
Views: 30710

Re: Mathematical Induction - Introductory Question

It's a proof by induction of the statement "every natural number n is either even or odd" Another, simpler(and pretty trivial) proof by induction would be "every positive natural number n is divisible by 1" To prove that by induction, we follow the basic steps of induction: Base ...
by Demki
Mon May 01, 2017 4:12 pm UTC
Forum: Coding
Topic: Basic Question Involving Functions (Python)
Replies: 18
Views: 7302

Re: Basic Question Involving Functions (Python)

While I am not too well versed in python, I think it is better for you to think about these functions as procedures, or subroutines, basically they are there to divide up your code and eliminate a lot of rewriting code. Some languages allow passing functions as arguments to other functions, which ma...
by Demki
Fri Apr 21, 2017 6:12 pm UTC
Forum: Language/Linguistics
Topic: Miscellaneous language questions
Replies: 570
Views: 82167

Re: Miscellaneous language questions

I'd say yes because we don't have a year zero, thus years 1-10 form a decade
by Demki
Fri Apr 21, 2017 1:54 pm UTC
Forum: Mathematics
Topic: i want to learn factoring polynomial equation
Replies: 23
Views: 4327

Re: i want to learn factoring polynomial equation

doogly wrote:It also helps to practice polynomial long division. Like, what is 2x^3 + 3x^2 - x - 2 / x - 4 ?

That would be 2x^3 + 3x^2 - x - 2x^(-1) - 4
by Demki
Mon Apr 17, 2017 9:15 pm UTC
Forum: Mathematics
Topic: Qustion about 3D
Replies: 3
Views: 1830

Re: Qustion about 3D

Flumble wrote:(x' = y' = 0 is trivial, so I'll assume it's not considered)
x' = tanh(x+1)*y*z+1.37+(x+z)*ln(1+x^2+y^2+z^2)
y' = tanh(x)*z-cos(z+x)*y

I dare you to give a better projection.

Please show how this projects the Utah teapot
by Demki
Fri Apr 14, 2017 6:59 pm UTC
Forum: Religious Wars
Topic: What is log² x?
Replies: 11
Views: 5690

Re: What is log² x?

Well, a bigger ∘ fits with union and intersection notation, and I believe ∘ is closer to sets than to numbers. I also recall seeing + and × used instead of the sigma and pi somewhere - oh right it was a Youtube video talking about notation...

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