Search found 202 matches

by Demki
Tue Aug 08, 2017 10:42 pm UTC
Forum: Coding
Topic: var == 'value' vs 'value' == var
Replies: 17
Views: 2570

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: 826

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: 826

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: 36
Views: 2603

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: 36
Views: 2603

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: 2241

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: 1965

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: 988

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: 9712
Views: 1476546

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: 9712
Views: 1476546

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: 252
Views: 6476

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: 252
Views: 6476

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: 252
Views: 6476

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: 252
Views: 6476

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: 252
Views: 6476

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: 252
Views: 6476

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: 252
Views: 6476

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: 252
Views: 6476

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: 252
Views: 6476

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: 252
Views: 6476

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: 252
Views: 6476

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: 2833

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: 252
Views: 6476

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: 252
Views: 6476

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: 2833

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: 404
Views: 33822

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: 1935

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: 867

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: 1980

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...
by Demki
Fri Apr 14, 2017 12:04 am UTC
Forum: Religious Wars
Topic: What is log² x?
Replies: 11
Views: 1980

Re: What is log² x?

I'd write (log ∘ log)(x), and for variable(or large) function application, something like (o n log)(x) and maybe for a given sequence of functions (f m ,f m+1 ,f m+2 ...,f n-1 ,f n ), I'd write something like ( i=m o n f i )(x), similar to sigma notation and pi notation for sums and products, the ma...
by Demki
Wed Apr 12, 2017 8:06 pm UTC
Forum: Computer Science
Topic: Favorite Programming Language
Replies: 13
Views: 3492

Re: Favorite Programming Language

So far, every language I met had *some* use case where it shines, and *some* use case where it's a poor choice. What was Java's "shining" example? *runs* C#. I prefer Haskell tho. Hell, when I need a quick calculation(read: wait, what was sin (exp 3.12) again? Ah, right -0.61...), I just ...
by Demki
Wed Feb 22, 2017 1:35 pm UTC
Forum: Mathematics
Topic: Convert points from a 2d space with a real dimension x and an imaginary dimension y
Replies: 19
Views: 2121

Re: Convert points from a 2d space with a real dimension x and an imaginary dimension y

I'm not going to go and do a full Treatid on this issue [offtopic] This became a thing, now it's time to spread it in 4chan so everyone would use it without knowing what the hell it is. [/offtopic] MrY, are you looking for a transformation T from R^(2) to R^(2) such that for any pair of points x an...
by Demki
Wed Jan 18, 2017 1:57 pm UTC
Forum: Logic Puzzles
Topic: New puzzle : Equalize
Replies: 13
Views: 2375

Re: New puzzle : Equalize

Another "random" setup that doesn't have a unique solution:

Code: Select all

 
 bb
r  r
b  b
 rr

As it has at least 2 solutions:

Code: Select all

bbbb
rrrr
bbbb
rrrr

Code: Select all

bbbb
rbbr
brrb
rrrr
by Demki
Wed Jan 11, 2017 2:17 am UTC
Forum: Mathematics
Topic: Misunderstanding basic math concepts, help please?
Replies: 338
Views: 42842

Re: Misunderstanding basic math concepts, help please?

Ho boy! We have Demki insisting that I formally prove that it is impossible to formally prove (or define) anything. And this here shows you didn't read my post. I didn't ask you to prove that you can't prove anything. I asked you to use whatever methodology you propose to replace axiomatic mathemat...
by Demki
Mon Jan 09, 2017 9:05 pm UTC
Forum: Logic Puzzles
Topic: magic cube
Replies: 4
Views: 1441

Re: magic cube

"It was a joke"
by Demki
Sat Jan 07, 2017 6:39 pm UTC
Forum: Mathematics
Topic: Misunderstanding basic math concepts, help please?
Replies: 338
Views: 42842

Re: Misunderstanding basic math concepts, help please?

So far you have been rambling on and on about how we can't describe anything, so what makes the 'relationship of patterns of words' that you suggest not be included in the quantifier 'anything'? You have yet to show a single concrete example of how you would do things differently. Could you show wha...
by Demki
Mon Jan 02, 2017 5:35 am UTC
Forum: Coding
Topic: Coding: Fleeting Thoughts
Replies: 9712
Views: 1476546

Re: Coding: Fleeting Thoughts

Because floats cannot represent 1/100 exactly. Ah, ok. Makes sense. So if I did floor(length)==floor(width) then it wouldn't be wrong? (at least it wouldn't slither past the condition) If you did that you would indeed get it to terminate, it probably will not be after the expected number of iterati...
by Demki
Sun Jan 01, 2017 11:08 pm UTC
Forum: Coding
Topic: Coding: Fleeting Thoughts
Replies: 9712
Views: 1476546

Re: Coding: Fleeting Thoughts

So yes, you get the expected result for integers. So then, why is float length; float width; length = 10.0; for (width=1.0 ; width=width+.01 ; length==width) print ("still too long"); print ("Finally, perfect!"); wrong? Jose As Korona said, floating point values cannot accuratel...
by Demki
Sun Jan 01, 2017 4:37 pm UTC
Forum: Coding
Topic: Coding: Fleeting Thoughts
Replies: 9712
Views: 1476546

Re: Coding: Fleeting Thoughts

Seeing as floating point division is done by dividing the mantissa and subtracting the exponents, in the case of 6.0/3.0, you should get exactly 2.0, as the mantissa are 1.1 and 1.1, and the exponents would be 2 and 1( so we have (1.1 × 2^(2))/(1.1 × 2^(1)) so we get (1.1/1.1) × 2^(1), and since the...
by Demki
Fri Dec 30, 2016 2:20 am UTC
Forum: Language/Linguistics
Topic: Thinking in words, and noticing errors
Replies: 15
Views: 2771

Re: Thinking in words, and noticing errors

When you have a thought, do you tend to think it in words and sentences? Most of the times, yes, especially when writing text. My thinking has actually shifted from being mostly in Hebrew(first language) to English, probably due to the time I spent on the internet and thus reading a lot of English ...

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