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  • What is the § ± key for on Mac keyboards?

    - by Pat Wallace
    Apple's keyboards have a new key, with § and ± symbols on it. Can somebody tell me what these keys are for, and where I should use them? I am aware the symbols have mathematical uses, but I assume they must do something important as well to be on the core keyboard. Or are they just the 'Scroll Lock' of the Apple world?

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  • Drawing lattices online

    - by lavabo
    This isn't really a programming question but... Is there any way to draw online a lattice for a material, like a compound? i.e. a 3D gridlike pattern? I know there are some applications for drawing mathematical lattices, but the notation to me is unfamiliar - are there simply programs or applets or something for drawing lattices like in a compound?

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  • Add constant value to numeric XML attribute

    - by Dave Jarvis
    Background Add a constant value to numbers matched with a regular expression, using vim (gvim). Problem The following regular expression will match width="32": /width="\([0-9]\{2\}\)" Question How do you replace the numeric value of the width attribute with the results from a mathematical expression that uses the attribute's value? For example, I would like to perform the following global replacement: :%s/width="\([0-9]\{2\}\)"/width="\1+10"/g That would produce width="42" for width="32" and width="105" for width="95". Thank you!

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  • How to disable Events for a while in Javascript or jQuery

    - by Tarik
    Hello, I am wondering if you guys know different approach to disable an event for a while. Let me elaborate this more : Lets say I have a div or button which has a subscriber to its onclick event. To prevent the double click when the the methods are doing some ajax things, these are the some of the ways we can do : Disable the button till the method finishes its job Unbind till the methods finishes its job and then bind it again. Use some kind of flagging system like boolean so it will prevent method from working more than once. So is there any other ways, maybe some javascript tricks or jQuery tricks which is more efficient and better practice. Thanks in advance.

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  • How can I scale an image in a CSS sprite

    - by michael
    Hi, In this article, http://css-tricks.com/css-sprites/, it talks about how can I crop off a smaller image from 1 bigger image. Can you please tell me if it is possible/how I can crop off a smaller image and then scale the cropped off region before I lay it out? Here is an example from that article: A { background-image: url(http://www.jaredhirsch.com/coolrunnings/public_images/3deb155981/spriteme1.png); background-position: -10px -56px; } I would like to know how can I scale that image after I crop it from from spriteme1.png Here is the URL of the example: http://css-tricks.com/examples/CSS-Sprites/Example1After/ So I would like to know if I can make the icons next to Item1,2,3,4 smaller?

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  • UITableView: moving a row into an empty section

    - by Frank C
    I have a UITableView with some empty sections. I'd like the user to be able to move a row into them using the standard edit mode controls. The only way I can do it so far is to have a dummy row in my "empty" sections and try to hide it by using tableView:heightForRowAtIndexPath: to give the dummy row a height of zero. This seems to leave it as a 1-pixel row. I can probably hide this by making a special type of cell that's just filled with [UIColor groupTableViewBackgroundColor], but is there a better way? This is all in the grouped mode of UITableView UPDATE: Looks like moving rows into empty sections IS possible without any tricks, but the "sensitivity" is bad enough that you DO need tricks in order to make it usable for general users (who won't be patient enough to slowly hover the row around the empty section until things click)

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  • How to search for "R" materials?

    - by James Lavin
    "The Google" is very helpful... unless your language is called "R," in which case it spits out tons of irrelevant stuff. Anyone have any search engine tricks for "R"? There are some specialized websites, like those below, but how can you tell Google you mean "R" the language? If I'm searching for something specific, I'll use an R-specific term, like "cbind." Are there other such tricks? http://rweb.stat.umn.edu/R/doc/html/search/SearchEngine.html www.rseek.org http://search.r-project.org/ www.dangoldstein.com/search_r.html

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  • Xcode / Interface Builder - better workflow from designer to coder?

    - by tbarbe
    Were dealing with some pretty custom UI elements while building our OSX / Cocoa and iPhone / IPad apps. I was wondering if anyone has good recommendations or tricks for getting a better workflow between UI designers and coders while using Xcode / Interface Builder? It seems that many things require programmatic settings with UI editing in Cocoa... if you stray from the pre-built UI elements then you can't really easily drag-drop build a UI... instead we end up handing off a design doc ( photoshop/illustrator ) and then the poor developer has to deal with recreating this masterpiece in code or by using interface builder - usually a combination of both. This work flow is leading us to not so great results and we have to re-iterate around the UI elements to get them to work better. We love CSS and / or Flash designer to developer workflow where the UI could look exactly as it should and the hand off to developer was more seamless. Is there anyone out there who has some tricks - or insights into getting better workflow when using tools like Xcode / Interface Builder and doing Cocoa apps?

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  • Fast, Vectorizable method of taking floating point number modulus of special primes?

    - by caffiend
    Is there a fast method for taking the modulus of a floating point number? With integers, there are tricks for Mersenne primes, so that its possible to calculate y = x MOD 2^31 without needing division. Can any similar tricks be applied for floating point numbers? Preferably, in a way that can be converted into vector/SIMD operations, or moved into GPGPU code. The primes I'm interested in would be 2^7 and 2^31, although if there are more efficient ones for floating point numbers, those would be welcome.

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  • How do you make long SQL invoked from other code readable?

    - by Artem
    This is a very open question, but I think it can be very beneficial for SQL readability. So you have a Java program, and you are trying to call a monster SQL statement from it, with many subqueries and joins. The starting point for my question is a string constant like this: static string MONSTER_STATEMENT = "SELECT " + " fields" + "WHERE "+ " fieldA = (SELECT a FROM TableC) " + "AND fieldB IN (%s)" + "AND fieldC = %d " + "FROM " " tableA INNER JOIN tableB ON ..."; It later gets filled using String.format and executed. What are you tricks for making this kind of stuff readable? Do you separate your inner joins. Do you indent the SQL itself inside the string? Where do you put the comments? Please share all of the tricks in your arsenal.

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  • James Atkinson - New Blog Home

    - by jatkinson
    I'm migrating my blog that is currently hosted over at vbCity.com (which is an outstanding developer community!) to a new home at geekswithblogs.net. I truly appreciate the comradery of Serge B, Ged Mead, and the other team members at the "City". What you can expect to find here (my interests): Most .NET programming topics General computing Language examples in C#, VB.NET, and Boo WCF WPF Mathematical / GPS solutions F# (in progress... if you can say that much) Obsessed with code performance (speed) Some photography My background: Kansas State University Grad (Agriculture Technology Management) From Richmond, VA Self taught programmer (started with C# in VS2002) NOT a professional programmer (enables free thinking?!)  I'm no Jeff Atwood or Beth Massi, but you should expect to see some interesting stuff to follow.

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  • The Beginner’s Guide to Pidgin, the Universal Messaging Client

    - by Zainul Franciscus
    If you find chatting with multiple chat clients troublesome, then Pidgin is the tool for you. In today’s article, we’ll show you how to connect to popular chat networks, encrypt your conversations, and render mathematical formula in Pidgin Latest Features How-To Geek ETC How to Use the Avira Rescue CD to Clean Your Infected PC The Complete List of iPad Tips, Tricks, and Tutorials Is Your Desktop Printer More Expensive Than Printing Services? 20 OS X Keyboard Shortcuts You Might Not Know HTG Explains: Which Linux File System Should You Choose? HTG Explains: Why Does Photo Paper Improve Print Quality? Natural Wood Grain Icons for Your Desktop and App Launcher Docks My Blackberry Is Not Working! The Apple Too?! [Funny Video] Hidden Tracks Your Stolen Mac; Free Until End of January Why the Other Checkout Line Always Moves Faster World of Warcraft Theme for Windows 7 Ubuntu Font Family Now Available for Download

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  • Difference Procedural Generation and Random Generation

    - by U-No-Poo
    Today, I got into an argument about the term "procedural generation". My point was that its different from "classic" random generation in the way that procedural is based on a more mathematical, fractal based, algorithm leading to a more "realistic" distribution and the usual randomness of most languages are based on a pseudo-random-number generator, leading to an "unrealistic", in a way, ugly, distribution. This discussion was made with a heightmap in mind. The discussion left me somehow unconvinced about my own arguments though, so, is there more to it? Or am I the one who is, in fact, simply wrong?

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  • NET Math Libraries

    - by JoshReuben
    NET Mathematical Libraries   .NET Builder for Matlab The MathWorks Inc. - http://www.mathworks.com/products/netbuilder/ MATLAB Builder NE generates MATLAB based .NET and COM components royalty-free deployment creates the components by encrypting MATLAB functions and generating either a .NET or COM wrapper around them. .NET/Link for Mathematica www.wolfram.com a product that 2-way integrates Mathematica and Microsoft's .NET platform call .NET from Mathematica - use arbitrary .NET types directly from the Mathematica language. use and control the Mathematica kernel from a .NET program. turns Mathematica into a scripting shell to leverage the computational services of Mathematica. write custom front ends for Mathematica or use Mathematica as a computational engine for another program comes with full source code. Leverages MathLink - a Wolfram Research's protocol for sending data and commands back and forth between Mathematica and other programs. .NET/Link abstracts the low-level details of the MathLink C API. Extreme Optimization http://www.extremeoptimization.com/ a collection of general-purpose mathematical and statistical classes built for the.NET framework. It combines a math library, a vector and matrix library, and a statistics library in one package. download the trial of version 4.0 to try it out. Multi-core ready - Full support for Task Parallel Library features including cancellation. Broad base of algorithms covering a wide range of numerical techniques, including: linear algebra (BLAS and LAPACK routines), numerical analysis (integration and differentiation), equation solvers. Mathematics leverages parallelism using .NET 4.0's Task Parallel Library. Basic math: Complex numbers, 'special functions' like Gamma and Bessel functions, numerical differentiation. Solving equations: Solve equations in one variable, or solve systems of linear or nonlinear equations. Curve fitting: Linear and nonlinear curve fitting, cubic splines, polynomials, orthogonal polynomials. Optimization: find the minimum or maximum of a function in one or more variables, linear programming and mixed integer programming. Numerical integration: Compute integrals over finite or infinite intervals, over 2D and higher dimensional regions. Integrate systems of ordinary differential equations (ODE's). Fast Fourier Transforms: 1D and 2D FFT's using managed or fast native code (32 and 64 bit) BigInteger, BigRational, and BigFloat: Perform operations with arbitrary precision. Vector and Matrix Library Real and complex vectors and matrices. Single and double precision for elements. Structured matrix types: including triangular, symmetrical and band matrices. Sparse matrices. Matrix factorizations: LU decomposition, QR decomposition, singular value decomposition, Cholesky decomposition, eigenvalue decomposition. Portability and performance: Calculations can be done in 100% managed code, or in hand-optimized processor-specific native code (32 and 64 bit). Statistics Data manipulation: Sort and filter data, process missing values, remove outliers, etc. Supports .NET data binding. Statistical Models: Simple, multiple, nonlinear, logistic, Poisson regression. Generalized Linear Models. One and two-way ANOVA. Hypothesis Tests: 12 14 hypothesis tests, including the z-test, t-test, F-test, runs test, and more advanced tests, such as the Anderson-Darling test for normality, one and two-sample Kolmogorov-Smirnov test, and Levene's test for homogeneity of variances. Multivariate Statistics: K-means cluster analysis, hierarchical cluster analysis, principal component analysis (PCA), multivariate probability distributions. Statistical Distributions: 25 29 continuous and discrete statistical distributions, including uniform, Poisson, normal, lognormal, Weibull and Gumbel (extreme value) distributions. Random numbers: Random variates from any distribution, 4 high-quality random number generators, low discrepancy sequences, shufflers. New in version 4.0 (November, 2010) Support for .NET Framework Version 4.0 and Visual Studio 2010 TPL Parallellized – multicore ready sparse linear program solver - can solve problems with more than 1 million variables. Mixed integer linear programming using a branch and bound algorithm. special functions: hypergeometric, Riemann zeta, elliptic integrals, Frensel functions, Dawson's integral. Full set of window functions for FFT's. Product  Price Update subscription Single Developer License $999  $399  Team License (3 developers) $1999  $799  Department License (8 developers) $3999  $1599  Site License (Unlimited developers in one physical location) $7999  $3199    NMath http://www.centerspace.net .NET math and statistics libraries matrix and vector classes random number generators Fast Fourier Transforms (FFTs) numerical integration linear programming linear regression curve and surface fitting optimization hypothesis tests analysis of variance (ANOVA) probability distributions principal component analysis cluster analysis built on the Intel Math Kernel Library (MKL), which contains highly-optimized, extensively-threaded versions of BLAS (Basic Linear Algebra Subroutines) and LAPACK (Linear Algebra PACKage). Product  Price Update subscription Single Developer License $1295 $388 Team License (5 developers) $5180 $1554   DotNumerics http://www.dotnumerics.com/NumericalLibraries/Default.aspx free DotNumerics is a website dedicated to numerical computing for .NET that includes a C# Numerical Library for .NET containing algorithms for Linear Algebra, Differential Equations and Optimization problems. The Linear Algebra library includes CSLapack, CSBlas and CSEispack, ports from Fortran to C# of LAPACK, BLAS and EISPACK, respectively. Linear Algebra (CSLapack, CSBlas and CSEispack). Systems of linear equations, eigenvalue problems, least-squares solutions of linear systems and singular value problems. Differential Equations. Initial-value problem for nonstiff and stiff ordinary differential equations ODEs (explicit Runge-Kutta, implicit Runge-Kutta, Gear's BDF and Adams-Moulton). Optimization. Unconstrained and bounded constrained optimization of multivariate functions (L-BFGS-B, Truncated Newton and Simplex methods).   Math.NET Numerics http://numerics.mathdotnet.com/ free an open source numerical library - includes special functions, linear algebra, probability models, random numbers, interpolation, integral transforms. A merger of dnAnalytics with Math.NET Iridium in addition to a purely managed implementation will also support native hardware optimization. constants & special functions complex type support real and complex, dense and sparse linear algebra (with LU, QR, eigenvalues, ... decompositions) non-uniform probability distributions, multivariate distributions, sample generation alternative uniform random number generators descriptive statistics, including order statistics various interpolation methods, including barycentric approaches and splines numerical function integration (quadrature) routines integral transforms, like fourier transform (FFT) with arbitrary lengths support, and hartley spectral-space aware sequence manipulation (signal processing) combinatorics, polynomials, quaternions, basic number theory. parallelized where appropriate, to leverage multi-core and multi-processor systems fully managed or (if available) using native libraries (Intel MKL, ACMS, CUDA, FFTW) provides a native facade for F# developers

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  • Raycasting tutorial / vector math question

    - by mattboy
    I'm checking out this nice raycasting tutorial at http://lodev.org/cgtutor/raycasting.html and have a probably very simple math question. In the DDA algorithm I'm having trouble understanding the calcuation of the deltaDistX and deltaDistY variables, which are the distances that the ray has to travel from 1 x-side to the next x-side, or from 1 y-side to the next y-side, in the square grid that makes up the world map (see below screenshot). In the tutorial they are calculated as follows, but without much explanation: //length of ray from one x or y-side to next x or y-side double deltaDistX = sqrt(1 + (rayDirY * rayDirY) / (rayDirX * rayDirX)); double deltaDistY = sqrt(1 + (rayDirX * rayDirX) / (rayDirY * rayDirY)); rayDirY and rayDirX are the direction of a ray that has been cast. How do you get these formulas? It looks like pythagorean theorem is part of it, but somehow there's division involved here. Can anyone clue me in as to what mathematical knowledge I'm missing here, or "prove" the formula by showing how it's derived?

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  • Any idea for a master thesis in software engineering

    - by medusa
    Hi! I have to choose a thesis for my master degree. Time is limited to about 6 months. Do you have any idea? Any personal thesis that was successful? After searching around for some time now, i see the most famous topics are related to artificial intelligence, but i don't want something like that, because most of it would be just theory and boring. A lot of students present these kind of studies because those are the most difficult. I would prefer something that does not necessary include that mathematical complexity but which is an everyday-life topic, and gives concrete ideas, hypothesis, or solutions to some actual problems. Hope i gave my whole idea: i am looking for something that is different from the majority of what all students do, and able to impress the audience... :) I would really really appreciate any your suggestion, Thank you!

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  • How will Quantum computing affect us?

    - by CiscoIPPhone
    I am interested in quantum computing, but have not studied it in depth. Things like Shor's algorithm intrigue me. My question is: If quantum computing took off in a big way (i.e. functional quantum home computers were available) how would it affect us programmers and software developers? Would we have to learn how to make use of superposition and entanglement - would it change how we write algorithms? Would more mathematical programmers be required/would we need new skills? Would it change nothing at all from our perspective (i.e. would it be abstracted)? Your opinion is welcome.

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  • How does a website like Mathway work?

    - by Bob
    I recently found a website called Mathway Basically, it works by allowing you to choose your "level of math" (which it uses to determine what tools it should provide to you) and then allows you to input a math problem which it then solves for you, and gives you detailed solutions (you have to try it, it's really cool). I was wondering how it worked on two levels. First off, how would they parse the math problem (and all the sometimes foreign mathematical operators)? How do they get from text to numbers, variables, and operators? Second, how do they generate the explanations? While you have to pay for the detailed solutions (which are explanations of how they solved the problem), I've seen their preview screenshots, and it looks very detailed. The explanations are given in full, accurate sentences. How would they generate something like that?

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  • What is the justification for Python's power operator associating to the right?

    - by Pieter Müller
    I am writing code to parse mathematical expression strings, and noticed that the order in which chained power operators are evaluated in Python differs from the order in Excel. From http://docs.python.org/reference/expressions.html: "Thus, in an unparenthesized sequence of power and unary operators, the operators are evaluated from right to left (this does not constrain the evaluation order for the operands): -1*2 results in -1."* This means that, in Python: 2**2**3 is evaluated as 2**(2**3) = 2**8 = 256 In Excel, it works the other way around: 2^2^3 is evaluated as (2^2)^3 = 4^3 = 64 I now have to choose an implementation for my own parser. The Excel order is easier to implement, as it mirrors the evaluation order of multiplication. I asked some people around the office what their gut feel was for the evaluation of 2^2^3 and got mixed responses. Does anybody know of any good reasons or conciderations in favour of the Python implementation? And if you don't have an answer, please comment with the result you get from gut feel - 64 or 256?

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  • Doing an SNES Mode 7 (affine transform) effect in pygame

    - by 2D_Guy
    Is there such a thing as a short answer on how to do a Mode 7 / mario kart type effect in pygame? I have googled extensively, all the docs I can come up with are dozens of pages in other languages (asm, c) with lots of strange-looking equations and such. Ideally, I would like to find something explained more in English than in mathematical terms. I can use PIL or pygame to manipulate the image/texture, or whatever else is necessary. I would really like to achieve a mode 7 effect in pygame, but I seem close to my wit's end. Help would be greatly appreciated. Any and all resources or explanations you can provide would be fantastic, even if they're not as simple as I'd like them to be. If I can figure it out, I'll write a definitive how to do mode 7 for newbies page. edit: mode 7 doc: http://www.coranac.com/tonc/text/mode7.htm

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  • Rotate sphere in Javascript / three.js while moving on x/z axes

    - by kaipr
    I have a sphere/ball in three.js which I want to "roll" arround on a x/z axis. For the z axe I could simply do this no matter what the current x and y rotation is: sphere.roll_z = function(distance) { sphere.position.z += distance; sphere.rotation.x += distance > 0 ? 0.05 : -0.05; } But how can I roll it along the x axe? And how could I properly do the roll_z? I've found a lot about quateration and matrixes, but I can't figure out how to use them properly to achieve my (rather simple) goal. I'm aware that I have to update multiple rotations and that I have to calculate how far to rotate the sphere to match the distance, but the "how" is the question. It's probably just lack of mathematical skills which I should train, but a working example/short explanation would help alot to start with.

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  • Good book or tutorial for learning how to apply integration methods

    - by Cumatru
    I'm looking to animate a graph layout using edges as springs and nodes as weights ( a node with more links will have a bigger weight ). I'm not capable of wrapping my head around the usage of mathematical and physics relations in my application. As far as i read, Runge Kutta 4 ( preferably ) or Verlet will be a good choice, but i have problems with understanding how they really work, and what physics equations should i apply. If i can't understand them, i can't use them. I'm looking for a book or a tutorial which describe the things that i need.

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  • Is functional programming a superset of object oriented?

    - by Jimmy Hoffa
    The more functional programming I do, the more I feel like it adds an extra layer of abstraction that seems like how an onion's layer is- all encompassing of the previous layers. I don't know if this is true so going off the OOP principles I've worked with for years, can anyone explain how functional does or doesn't accurately depict any of them: Encapsulation, Abstraction, Inheritance, Polymorphism I think we can all say, yes it has encapsulation via tuples, or do tuples count technically as fact of "functional programming" or are they just a utility of the language? I know Haskell can meet the "interfaces" requirement, but again not certain if it's method is a fact of functional? I'm guessing that the fact that functors have a mathematical basis you could say those are a definite built in expectation of functional, perhaps? Please, detail how you think functional does or does not fulfill the 4 principles of OOP.

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