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• How could there still not be a mysqldb module for Python 3?

  - by itsadok

  This SO question is now more than two years old. MySQL is an incredibly popular database engine, Python is an incredibly popular programming language, and Python 3 has been officially released two years ago, and was available even before that. What's more, the whole mysqldb module is just a layer translating Python's db-api to MySQL's API. It's not that big of a library. I must be missing something here. How come almost* nobody in the entire open source community has spent the (I'm guessing) two weeks it takes to port this lib? Is Python 3 that unpopular? Is the combination of python and mysql not as common as I assume? Or maybe it's just a lot harder to port mysqldb than I assume? Anyone know the inside story on this? * Now I see that this guy has done it, which takes some of the wind out of my question, but it still seems to little and too late to make sense.

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• Using machine learning to aim mirrors in a solar array?

  - by Buttons840

  I've been thinking about solar collectors where several independent mirrors to focus the light on a solar collector, similar to the following design from Energy Innovations. Because there will be flaws in the assembly of this solar array, I am proceeding with the following assumptions (or lack thereof): The software knows the "position" of each mirror, but doesn't know how this position relates to the real world or to other mirrors. This will account for poor mirror calibration or other environmental factors which may effect one mirror but not the others. If a mirror moves 10 units in one direction, and then 10 units in the opposite direction, it will end up where it originally started. I would like to use machine learning to position the mirrors correctly and focus the light on the collector. I expect I would approach this as an optimization problem, optimizing the mirror positions to maximize the heat inside the collector and the power output. The problem is finding a small target in a noisy high-dimensional space (considering each mirror has 2 axis of rotation). Some of the problems I anticipate are: cloudy days, even if you stumble upon the perfect mirror alignment, it might be cloudy at the time noisy sensor data the sun is a moving target, it moves along a path, and follows a different path every day - although you could calculate the exact position of the sun at any time, you wouldn't know how that position relates to your mirrors My question isn't about the solar array, but possible machine learning techniques that would help in this "small target in a noisy high dimensional-space" problem. I mentioned the solar array because it was the catalyst for this question and a good example. What machine learning techniques can find such a small target in a noisy high-dimensional space? EDIT: A few additional thoughts: Yes, you can calculate the suns position in the real world, but you don't know how the mirrors position is related to the real world (unless you've learned it somehow). You might know the suns azimuth is 220 degrees, and the suns elevation is 60 degrees, and you might know a mirror is at position (-20, 42); now tell me, is that mirror correctly aligned with the sun? You don't know. Lets assume you have some very sophisticated heat measurements, and you know "with this heat level, there must be 2 mirrors correctly aligned". Now the question is, which two mirrors (out of 25 or more) are correctly aligned? One solution I considered was to approximate the correct "alignment function" using a neural network which would take the suns azimuth and elevation as input and output a large array with 2 values for each mirror which correspond to the 2 axis of each mirror. I'm not sure what the best training method is though.

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• Would you use UML if it kept stakeholders from requesting changes frequently?

  - by Huperniketes

  As much as programmers hate to document their code/system and draw UML (especially, Sequencing, Activity and State machine diagrams) or other diagramming notation, would you agree to do it if it kept managers from requesting a "minor change" every couple of weeks? IOW, would you put together visual models to document the system if it helped you demonstrate to managers what the effect of changes are and why it takes so long to implement them? (Edited to help programmers understand what type of answer I'm looking for.) 2nd edit: Restating my question again, "Would you be willing to use some diagramming notation, against your better nature as a programmer, if it helped you manage change requests?" This question isn't asking if there might be something wrong with the process. It's a given that there's something wrong with the process. Would you be willing to do more work to improve it?

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• null values vs "empty" singleton for optional fields

  - by Uko

  First of all I'm developing a parser for an XML-based format for 3D graphics called XGL. But this question can be applied to any situation when you have fields in your class that are optional i.e. the value of this field can be missing. As I was taking a Scala course on coursera there was an interesting pattern when you create an abstract class with all the methods you need and then create a normal fully functional subclass and an "empty" singleton subclass that always returns false for isEmpty method and throws exceptions for the other ones. So my question is: is it better to just assign null if the optional field's value is missing or make a hierarchy described above and assign it an empty singleton implementation?

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• Flash Webcam non responsive

  - by powerbuoy

  I've got the same problem as this gentleman: https://answers.launchpad.net/ubuntu/+source/flashplugin-nonfree/+question/176541 Where the webcam settings / access does not work at all / is completely unresponsive in Ubuntu 11.10. I've tried webcam access in Facebook, Google+, my own code + a number of tutorials/demos and none work. What happens is the settings dialogue is completely unresponsive. Clicking tabs or buttons does nothing. In the question linked to a suggested answer is to run Unity 2D. Unfortunately this does not work for me (the exact same thing happens). I've also tried Gnome 3 which also does not work. Note that it is only the webcam settings that don't work. YouTube videos and annoying banners work just fine. Does anyone know of a workaround for this (except going back to 11.04) or if they've fixed this in 12.04? - also, are any of you experiencing the same thing?

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• What is the correct way to install ATI Catalyst Video Drivers in 12.04 LTS?

  - by Stephen Myall

  I am planning on doing a fresh install of 12.04 LTS next weekend (I am currently on Beta) and want to know what is the correct way to install ATI Catalyst Video Drivers in 12.04 LTS? I have been reviewing all the Q&A on AU and the reason for asking this specific question is that I maybe be missing some dependencies from my planned coding. In a previous AU question relating to 11.10 (here) NOT 12.04 the accepted response stated that this was a dependency. sudo apt-get install ia32-libs I was also receiving conflicting advice on other websites which put doubts on what the correct approach was.

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• Recommended certification to join in a game development internship [on hold]

  - by Conrado Costa

  I'm Brazilian and I'll go to California in July 2014 to study for 1 year and I'm intending to get a winter internship in the game development industry. I'm a programmer since 2008 and I know C#, PHP, Java, Python and a bit of Perl. My question is: do you know any certified required (or helpful) to get a winter job as a game developer? I have no problem to learn new languages, I'm thinking to get a C or C++ certified because I'm not sure about which is the most used language, but before to start a study marathon to take a certification, I have to choose the language and the certification itself. Can you help me, and is that a valid question?

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• PostgreSQL data diff

  - by skanatek

  Note: this question is not about syncing database schema/structure Problem In my web application I have a PostgreSQL database server (PGS) and a (separate machine) business logic server (BLS) which regularly (every minute or two) queries 'SELECT ALL' against PGS. The problem is that the 'SELECT ALL' query can easily return 50-200 MB each time. It is obvious that it would be not so good architecture-wise to transfer so much data so frequently over the web. Possible solution What I would like to do is to run some diff tool on PGS and compare the new query with the previous query (all this should be done on PGS). Once the comparison is done I would like to get a dump from PGS and transfer it to BLS. I expect that a diff-based dump would be much, much smaller than the whole 'SELECT ALL' query. Question Is there any data diff tool for PostgreSQL that can do diffs that compare PostgreSQL data between 2 tables or 2 dumps? Note: I would prefer some open-source software tool.

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• What php programmer should know?

  - by emchinee

  I've dig the database here and didn't found any answer for my question. What is a standard for a php programmer to know? I mean, literally, what group of language functions, mechanisms, variables should person know to consider oneself a (good) php programmer? (I know 'being good' is beyond language syntax, still I'm considering syntax of plain php only) To give an example what I mean: functions to control http sessions, cookies functions to control connection with databases functions to control file handling functions to control xml etc.. I omit phrases like 'security' or 'patterns' or 'framework' intentionally as it applies to every programming language. Hope I made myself clear, any input appreciated :) Note: Michael J.V. is right claiming that databases are independent from language, so to put my question more precisely and emphasise differences: Practises or security, are some ideas to implement (there is no 'Pattern' object with 'Decorator()' method, is there?) while using databases means knowing a mysqli and a set of its methods.

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• How can I attach a model to the bone of another model?

  - by kaykayman

  I am trying to attach one animated model to one of the bones of another animated model in an XNA game. I've found a few questions/forum posts/articles online which explain how to attach a weapon model to the bone of another model (which is analogous to what I'm trying to achieve), but they don't seem to work for me. So as an example: I want to attach Model A to a specific bone in Model B. Question 1. As I understand it, I need to calculate the transforms which are applied to the bone on Model B and apply these same transforms to every bone in Model A. Is this right? Question 2. This is my code for calculating the Transforms on a specific bone. private Matrix GetTransformPaths(ModelBone bone) { Matrix result = Matrix.Identity; while (bone != null) { result = result * bone.Transform; bone = bone.Parent; } return result; } The maths of Matrices is almost entirely lost on me, but my understanding is that the above will work its way up the bone structure to the root bone and my end result will be the transform of the original bone relative to the model. Is this right? Question 3. Assuming that this is correct I then expect that I should either apply this to each bone in Model A, or in my Draw() method: private void DrawModel(SceneModel model, GameTime gametime) { foreach (var component in model.Components) { Matrix[] transforms = new Matrix[component.Model.Bones.Count]; component.Model.CopyAbsoluteBoneTransformsTo(transforms); Matrix parenttransform = Matrix.Identity; if (!string.IsNullOrEmpty(component.ParentBone)) parenttransform = GetTransformPaths(model.GetBone(component.ParentBone)); component.Player.Update(gametime.ElapsedGameTime, true, Matrix.Identity); Matrix[] bones = component.Player.GetSkinTransforms(); foreach (SkinnedEffect effect in mesh.Effects) { effect.SetBoneTransforms(bones); effect.EnableDefaultLighting(); effect.World = transforms[mesh.ParentBone.Index] * Matrix.CreateRotationY(MathHelper.ToRadians(model.Angle)) * Matrix.CreateTranslation(model.Position) * parenttransform; effect.View = getView(); effect.Projection = getProjection(); effect.Alpha = model.Opacity; } } mesh.Draw(); } I feel as though I have tried every conceivable way of incorporating the parenttransform value into the draw method. The above is my most recent attempt. Is what I'm trying to do correct? And if so, is there a reason it doesn't work? The above Draw method seems to transpose the models x/z position - but even at these wrong positions, they do not account for the animation of Model B at all. Note: As will be evident from the code my "model" is comprised of a list of "components". It is these "components" that correspond to a single "Microsoft.Xna.Framework.Graphics.Model"

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• Why do people think SOAP is deprecated?

  - by user98q37479

  While browsing SO today I found this question here and it starts with this: Sure, you're gonna tell me that SOAP is depracated and all, well i'm forced to use it Found lots of statement like this one on SO up till now, this one just triggered me to ask this question. REST has its uses, SOAP has its uses, in some places they intersect as functionality but they are not replaceable to one another. So I wonder, why do people think SOAP is "deprecated"? Is it ignorance? Complexity of SOAP and WS-* specs? REST hype? What? If you think SOAP is deprecated please tell me why. I'm curious!

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• Splitting Graph into distinct polygons in O(E) complexity

  - by Arthur Wulf White

  If you have seen my last question: trapped inside a Graph : Find paths along edges that do not cross any edges How do you split an entire graph into distinct shapes 'trapped' inside the graph(like the ones described in my last question) with good complexity? What I am doing now is iterating over all edges and then starting to traverse while always taking the rightmost turn. This does split the graph into distinct shapes. Then I eliminate all the excess shapes (that are repeats of previous shapes) and return the result. The complexity of this algorithm is O(E^2). I am wondering if I could do it in O(E) by removing edges I already traversed previously. My current implementation of that returns unexpected results.

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• Pro Google App Engine developer interview questions (with answers)

  - by WooYek

  What are good questions to determine if applicant is pro Google App Engine developer? Questions that can distinguish that someone is not an ad-hoc GAE programmer, but is really doing professional GAE development, with all areas concerned (eg. performance, transactions, async/batch data processing). Please provide answers, so an intermediate developer (such as myself :) can interview someone more experienced. Please avoid open questions. If possible please provide a link to a documentation part that's covering a topic in question. Please keep one interview question/answer per response for better reading experience and easier interview preparation.

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• Mod_rewrite and urls that don't end with .php

  - by Kevin Laity

  I'm trying to use Mod_rewrite to hide the .php extensions of my pages. However, it refuses to do any rewriting unless the input url ends with .php, which makes that impossible. I can confirm that rewriting works fine as long as the url has .php at the end. RewriteRule a\.php b\.php Works, while RewriteRule a\.html b\.html does not. How can I turn off this behavior and allow it to rewrite all urls? I'm on a shared host so whatever I do has to be done from a .htaccess file. Update: There seems to be some confusion about what I'm asking here. The question is not about how to write the rule, the question is about server configuration. The rule I'm using is fine, I can test that locally. But the server I'm working with is somehow configured so that mod_rewrite doesn't attempt to rewrite anything that doesn't end with .php

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• Starting java processes with Upstart

  - by user265330

  I want to start a java process using Upstart. Currently, on our OpenSuSE servers, I use the System V init system to achieve this, but on our Ubuntu servers I'd rather use Upstart. But I have two questions... I have an Upstart job (a task) that configures the server, called, say, myconfig. And in the job that starts my java processes I ostensibly have: start on stopped myconfig exec /path/to/myjavastartscript.sh myjavastartscript.sh runs 'java -classpath blah MyClass'. In System V init, starting the service runs 'nohup /path/to/myjavastartscript.sh &'. So my first question is whether I still need to do the nohup or run-in-background with the exec command? When running, MyClass starts other Java processes. In System V init, the service stop just looks for java processes owned by a certain user and kills them. My second question is how could I control the termination of these processes with Upstart?

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• Is Haskell worth learning?

  - by Jason K

  I am looking at this question primarily from a career point of view, so I hope you answer it accordingly. I am fairly proficient with Python, can write C++ and I am a final year student of computer science engineering I am looking to learn Haskell because I have heard a lot about it. My question is: apart from learning it because of all the good I have heard about it, is it any good for my career? Is it used in the industry? I am curious to learn it but unless it helps me somehow in my career, I am not willing to make that change at this stage. Looking for some personal experiences here. Thanks!

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• flash twitter and facebook widgets

  - by NorthPole

  I'm stuck with a crappy digital signage platform that only renders .html and .swf files (and rss feeds) No customization of rss, only way to show something dynamic in a pretty way is to use flash. The question: is there any way to embed javascript in swf files or somehow have facebook and twitter flash plugins? I looked for ready-made swf widgets for the job but didn't find any, if there is any flash widget that serves a facebook and/or twitter feed please give me a link. (sorry if the question is out of context but these things usually run a stripped-down browser to display everything so its pretty much a web page run from a file and not a web server)

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• How can calculus and linear algebra be useful to a system programmer?

  - by Victor

  I found a website saying that calculus and linear algebra are necessary for System Programming. System Programming, as far as I know, is about osdev, drivers, utilities and so on. I just can't figure out how calculus and linear algebra can be helpful on that. I know that calculus has several applications in science, but in this particular field of programming I just can't imagine how calculus can be so important. The information was on this site: http://www.wikihow.com/Become-a-Programmer Edit: Some answers here are explaining about algorithm complexity and optimization. When I made this question I was trying to be more specific about the area of System's Programming. Algorithm complexity and optimization can be applied to any area of programming not just System's Programming. That may be why I wasn't able to came up with such thinking at the time of the question.

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• Programmer desk: L-shaped (corner) or rectangular? [closed]

  - by GoodEnough

  I'm thinking about switching my L-shaped desk for a rectangular one, but since I can't try before actually buying the desk, I'd like to know what other people think about the matter. Is it simply a matter of preference? What are the pros and cons of each type of desk? Also, I'm guessing a rather deep desk is necessary (I was thinking over 70cm/27''). Btw, I'm aware of this question, but it doesn't talk about this specific point. Same question on StackOverflow for anyone interested in an answer.

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• Narrow-phase collision detection algorithms

  - by Marian Ivanov

  There are three phases of collision detection. Broadphase: It loops between all objecs that can interact, false positives are allowed, if it would speed up the loop. Narrowphase: Determines whether they collide, and sometimes, how, no false positives Resolution: Resolves the collision. The question I'm asking is about the narrowphase. There are multiple algorithms, differing in complexity and accuracy. Hitbox intersection: This is an a-posteriori algorithm, that has the lowest complexity, but also isn't too accurate, Color intersection: Hitbox intersection for each pixel, a-posteriori, pixel-perfect, not accuratee in regards to time, higher complexity Separating axis theorem: This is used more often, accurate for triangles, however, a-posteriori, as it can't find the edge, when taking last frame in account, it's more stable Linear raycasting: A-priori algorithm, useful for semi-realistic-looking physics, finds the intersection point, even more accurate than SAT, but with more complexity Spline interpolation: A-priori, even more accurate than linear rays, even more coplexity. There are probably many more that I've forgot about. The question is, in when is it better to use SAT, when rays, when splines, and whether there is anything better.

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• Already have Merchant Account, what info will my Gateway need?

  - by Anonymous Coward

  I have a client who already has a merchant account for their physical store. What specific information about the merchant account will my client need to get from his bank to link it up to an online payment gateway that we will be using for the store? -----edits below -"my merchant account" changed to "the merchant account" -It is noted that my client will need to get a "high-risk" merchant account separate from his existing physical stores merchant account. -Though the question is essentially answered, for clarification: We plan to minimize our PCI compliance needs by utilizing something like Braintree's Transparent Redirect or the CRESecure iForm. So the gateway we would need to give the merchant account info to would be either of those two. Though, the CRESecure method would have yet one more step added into the mix since they would forward data to another payment provider. It is now assumed that the best place to field this question is to the support team at Braintree or CRESecure.

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• Manual bootstrapping with Juju on VPS

  - by aaronfc

  I recently bought a VPS (OpenVZ) with Ubuntu 13.04. Lately I've read about Juju and I thought it would match my needs on my brand new VPS as I want to easily configure Hadoop, Wordpress, Graphite and other services. I tried the juju-local approach but I got an error while installing it: http://paste.ubuntu.com/6373143/ So I got to #juju IRC channel and I was told to use "Manual bootstrapping" and create a question here in order to get more info as it seems is something under development. Could anybody help me getting Juju to work on my VPS? Did any had the same problem? Thanks in advance! EDIT: After some more research (and after reading my own question) I think I should clarify a little more the situation. What I want is a manual provider to allow me manage my VPS from Juju. I know there might be a work in progress and I would appreciate any info regarding it's state and any possible solution :)

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• Transformation matrix that maps a window

  - by gbhall

  I'm currently learning OpenGL at uni, and they give us questions to help us learn (these are not worth anything), however I'm stuck on this one question and would have to travel over an hour and a half to uni for an answer. How do I do this question? Please include as many steps as you can, I want to be able to follow exactly how to do this. Find the transformation that maps a window whose lower left corner is at (1,1) and upper right corner is at (3,5) onto: The entire device screen whose dimension is (600, 500) A viewport that has lower left corner at (100,100) and upper right corner at (400,400) Edit: Damn sorry I should have added I am meant to find the matrix, so no code.

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• Liskov principle: violation by type-hinting

  - by Elias Van Ootegem

  According to the Liskov principle, a construction like the one below is invalid, as it strengthens a pre-condition. I know the example is pointless/nonsense, but when I last asked a question like this, and used a more elaborate code sample, it seemed to distract people too much from the actual question. //Data models abstract class Argument { protected $value = null; public function getValue() { return $this->value; } abstract public function setValue($val); } class Numeric extends Argument { public function setValue($val) { $this->value = $val + 0;//coerce to number return $this; } } //used here: abstract class Output { public function printValue(Argument $arg) { echo $this->format($arg); return $this; } abstract public function format(Argument $arg); } class OutputNumeric extends Output { public function format(Numeric $arg)//<-- VIOLATION! { $format = is_float($arg->getValue()) ? '%.3f' : '%d'; return sprintf($format, $arg->getValue()); } } My question is this: Why would this kind of "violation" be considered harmful? So much so that some languages, like the one I used in this example (PHP), don't even allow this? I'm not allowed to strengthen the type-hint of an abstract method but, by overriding the printValue method, I am allowed to write: class OutputNumeric extends Output { final public function printValue(Numeric $arg) { echo $this->format($arg); } public function format(Argument $arg) { $format = is_float($arg->getValue()) ? '%.3f' : '%d'; return sprintf($format, $arg->getValue()); } } But this would imply repeating myself for each and every child of Output, and makes my objects harder to reuse. I understand why the Liskov principle exists, don't get me wrong, but I find it somewhat difficult to fathom why the signature of an abstract method in an abstract class has to be adhered to so much stricter than a non-abstract method. Could someone explain to me why I'm not allowed to hind at a child class, in a child class? The way I see it, the child class OutputNumeric is a specific use-case of Output, and thus might need a specific instance of Argument, namely Numeric. Is it really so wrong of me to write code like this?

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• Naming: objectAction or actionObject?

  - by DocSalvage

  The question, Stored procedure Naming conventions?, and Joel's excellent Making Wrong Code Look Wrong article come closest to addressing my question, but I'm looking for a more general set of criteria to use in deciding how to name modules containing code (classes, objects, methods, functions, widgets, or whatever). English (my only human language) is structured as action-object (i.e closeFile, openFile, saveFile) and since almost all computer languages are based on English, this is the most common convention. However, in trying to keep related code close together and still be able to find things, I've found object-action (i.e. fileClose, fileOpen, fileSave) to be very attractive. Quite a number of non-English human languages follow this structure as well. I doubt that one form is universally superior, but when should each be used in the pursuit of helping to make sure bad code looks bad?

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