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• Find location using only distance and bearing?

  - by pinnacler

  Triangulation works by checking your angle to three KNOWN targets. "I know the that's the Lighthouse of Alexandria, it's located here (X,Y) on a map, and it's to my right at 90 degrees." Repeat 2 more times for different targets and angles. Trilateration works by checking your distance from three KNOWN targets. "I know the that's the Lighthouse of Alexandria, it's located here (X,Y) on a map, and I'm 100 meters away from that." Repeat 2 more times for different targets and ranges. But both of those methods rely on knowing WHAT you're looking at. Say you're in a forest and you can't differentiate between trees, but you know where key trees are. These trees have been hand picked as "landmarks." You have a robot moving through that forest slowly. Do you know of any ways to determine location based solely off of angle and range, exploiting geometry between landmarks? Note, you will see other trees as well, so you won't know which trees are key trees. Ignore the fact that a target may be occluded. Our pre-algorithm takes care of that. 1) If this exists, what's it called? I can't find anything. 2) What do you think the odds are of having two identical location 'hits?' I imagine it's fairly rare. 3) If there are two identical location 'hits,' how can I determine my exact location after I move the robot next. (I assume the chances of having 2 occurrences of EXACT angles in a row, after I reposition the robot, would be statistically impossible, barring a forest growing in rows like corn). Would I just calculate the position again and hope for the best? Or would I somehow incorporate my previous position estimate into my next guess? If this exists, I'd like to read about it, and if not, develop it as a side project. I just don't have time to reinvent the wheel right now, nor have the time to implement this from scratch. So if it doesn't exist, I'll have to figure out another way to localize the robot since that's not the aim of this research, if it does, lets hope it's semi-easy.

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• How to identify ideas and concepts in a given text

  - by Nick

  I'm working on a project at the moment where it would be really useful to be able to detect when a certain topic/idea is mentioned in a body of text. For instance, if the text contained: Maybe if you tell me a little more about who Mr Balzac is, that would help. It would also be useful if I could have a description of his appearance, or even better a photograph? It'd be great to be able to detect that the person has asked for a photograph of Mr Balzac. I could take a really naïve approach and just look for the word "photo" or "photograph", but this would obviously be no good if they wrote something like: Please, never send me a photo of Mr Balzac. Does anyone know where to start with this? Is it even possible? I've looked into things like nltk, but I've yet to find an example of someone doing something similar and am still not entirely sure what this kind of analysis is called. Any help that can get me off the ground would be great. Thanks!

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• Another word for Business Logic?

  - by herzmeister der welten

  What is another good word for Business Logic? Software might also run in civil service offices or for hobbyists, so I never felt that comfortable with using that term in certain modules and documentation. App Logic is too specific as well, because logic modules might also be used in services.

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• calculating parameters for defining subsections of quadratic bezier curves

  - by jedierikb

  I have a quadratic bezier curve described as (startX, startY) to (anchorX, anchorY) and using a control point(controlX, controlY). I have two questions: (1) I want to determine y points on that curve based on an x point. (2) Then, given two intermediary points on that bezier curve, I want to know the 6 parameters needed to create that mini-bezier curve.

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• How closely related is music composition to coding?

  - by ehsanul

  It seems to me as if there are a higher proportion of musicians in the programming field than in the general public. Maybe it's just an illusion caused by the fact that I'm an amateur guitarist myself, so I tend to notice coding musicians (or musical coders?) more. But I wonder if there really is some connection. Perhaps a shared set of skills or an innate quality that makes it more likely for someone who enjoys programming to also enjoy playing and composing music. How closely related is music composition to coding? I'd especially like to hear from the musicians around here.

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• How to write an algorithm to check if the sum of any two numbers in an array/list matches a given nu

  - by Bunny Rabbit

  How can I write an algorithm to check if the sum of any two numbers in an array/list matches a given number with a complexity of nlogn?

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• Most hazardous performance bottleneck misconceptions

  - by David Murdoch

  The guys who wrote Bespin (cloud-based canvas-based code editor [and more]) recently spoke about how they re-factored and optimize a portion of the Bespin code because of a misconception that JavaScript was slow. It turned out that when all was said and done, their optimization produced no significant improvements. I'm sure many of us go out of our way to write "optimized" code based on misconceptions similar to that of the Bespin team. What are some common performance bottleneck misconceptions developers commonly subscribe to?

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• What design pattern do you use the most?

  - by spoon16

  I'm interested in understanding what design patterns people find themselves using often. Hopefully this list will help other recognize common scenarios and the associated design pattern that can be used to solve them. Please describe a common problem you find yourself solving and the design pattern(s) you use to solve it. Links to blogs or documentation describing the pattern are also appreciated. Edit: Please expand on your answers a bit, I would like this to be a useful reference for someone who wants to learn more about design patterns and is curious on what situations a specific design pattern might be used. Nobody has linked to any "more learning" resources.

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• Drawing Directed Acyclic Graphs: Minimizing edge crossing?

  - by Robert Fraser

  Laying out the verticies in a DAG in a tree form (i.e. verticies with no in-edges on top, verticies dependent only on those on the next level, etc.) is rather simple without graph drawing algorithms such as Efficient Sugimiya. However, is there a simple algorithm to do this that minimizes edge crossing? (For some graphs, it may be impossible to completely eliminate edge crossing.) A picture says a thousand words, so is there an algorithm that would suggest: instead of: EDIT: As the picture suggests, a vertex's inputs are always on top and outputs are always below, which is another barrier to just pasting in an existing layout algorithm.

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• How/when to hire new programmers, and how to integrate them?

  - by Shaul

  Hiring new programmers, especially in a small company, can often present a Catch-22 situation. We have too much work to do, so we need to hire new programmers. But we can't hire new programmers now, because they will need mentoring and several months of learning curve in your industry/product/environment before they're useful, and none of the programmers has time to be a mentor to a new programmer, because they're all completely swamped with the current work load. That may be a slightly frivolous way of describing the situation, but nevertheless, it's difficult for a small company on a tight budget to justify hiring someone who is not only going to be unproductive for a long time, but will also take away from the performance of the current programmers. How have you dealt with this kind of situation? When is the best time to hire someone? What are the best tasks to assign to a new team member so that they can learn their way around your code base and start getting their hands dirty as quickly as possible? How do you get the new guy useful without bogging your existing programmers down in too much mentoring? Any comments & suggestions you have are much appreciated!

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• Literature and Tutorials for Writing a Ray Tracer

  - by grrussel

  I am interested in finding recommendations on books on writing a raytracer, simple and clear implementations of ray tracing that can be seen on the web, and online resources on introductory raytracing. Ideally, the approach would be incremental and tutorial in style, and explain both the programming techniques and underyling mathematics, starting from the basics.

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• Using Inch or cm/mm from metric system for americans and canadians?

  - by gamma

  We're developing an international product that displays a ruler to the user. Now in Germany and many other countries its of course common to use the metric system: cm or mm. I'm aware that americans and canadians (and maybe others too) do still use inches, feet and yards. So the question is: will todays americans (and other inch-country-citizens) understand the metric system and take it for granted - or do they still love their inches so much that they'd rather die than use a product with incorrect measurements? ( sorry for being blunt ;) )

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• Socket Sessions For Persistent Connections

  - by Olaseni

  I am developing a socket server where a client will be bound after being authenticated similar to SMPP. Is there support for cookies in this regard? How do you maintain a session for socket client that is "logged in"?

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• How do I call C from Go using the "foreign function interface"

  - by pauldoo

  Hi, How do I use Go's "foreign function interface" to call out to a C function? This interface is mentioned on the FAQ, but I cannot see it mentioned elsewhere in the docs.

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• English dictionary as txt or xml file with support of synonyms

  - by Simon

  Can someone point me to where I can download English dictionary as a txt or xml file. I am building a simple app for myself and looking for something what I could start using immediately without learning complex API. Support for synonyms would be great, that is it should be easier to retrieve all the synonyms for particular word. It would be absolutely fantastic if dictionary would be listing British and American spelling of the words where they are differ. Even if it would be small dictionary (few 000's words) that's ok, I only need it for small project. I even would be willing to buy one if the price is reasonable, and dictionary is easy to use - simple xml wold be great. Any directions please.

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• C#, weird optimization

  - by Snake

  Hi, I'm trying to read my compiled C# code. this is my code: using(OleDbCommand insertCommand = new OleDbCommand("...", connection)) { // do super stuff } But! We all know that a using gets translated to this: { OleDbCommand insertCommand = new OleDbCommand("...", connection) try { //do super stuff } finally { if(insertCommand != null) ((IDisposable)insertCommand).Dispose(); } } (since OleDbCommand is a reference type). But when I decompile my assembly (compiled with .NET 2.0) I get this in Resharper: try { insertCommand = new OleDbCommand("", connection); Label_0017: try { //do super stuff } finally { Label_0111: if ((insertCommand == null) != null) { goto Label_0122; } insertCommand.Dispose(); Label_0122:; } I'm talking about this line: if ((insertCommand == null) != null). True is not null, it never is, nor is false. So how is my object disposed properly? WTF? Thanks! -Kristof

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• Why do software engineers hate writing documentation?

  - by Stewart Johnson

  I ask because I quite enjoy it! I'm talking about design documentation and implementation notes (NOT user manuals), which are non-existent in most of the codebases I've been handed. I can understand why a developer wouldn't want to write requirements (that's the analyst's job) or the user documentation (that's a technical writer's job) but I don't get why developers hate writing design docs. I don't think I would feel as if I'd finished the job if I only wrote the code and walked away -- mainly because when I've been introduced to code-only situations I've seen how hard it is to figure out what's been done and what the software does. I would hate for people to suffer the same situation when inheriting my code. What makes you loath writing supporting documentation for your code?

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• Automatic tracking algorithm

  - by nico

  Hi everyone, I'm trying to write a simple tracking routine to track some points on a movie. Essentially I have a series of 100-frames-long movies, showing some bright spots on dark background. I have ~100-150 spots per frame, and they move over the course of the movie. I would like to track them, so I'm looking for some efficient (but possibly not overkilling to implement) routine to do that. A few more infos: the spots are a few (es. 5x5) pixels in size the movement are not big. A spot generally does not move more than 5-10 pixels from its original position. The movements are generally smooth. the "shape" of these spots is generally fixed, they don't grow or shrink BUT they become less bright as the movie progresses. the spots don't move in a particular direction. They can move right and then left and then right again the user will select a region around each spot and then this region will be tracked, so I do not need to automatically find the points. As the videos are b/w, I though I should rely on brigthness. For instance I thought I could move around the region and calculate the correlation of the region's area in the previous frame with that in the various positions in the next frame. I understand that this is a quite naïve solution, but do you think it may work? Does anyone know specific algorithms that do this? It doesn't need to be superfast, as long as it is accurate I'm happy. Thank you nico

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• Method of transforming 3D vectors with a matrix

  - by Drew Noakes

  I've been doing some reading on transforming Vector3 with matrices, and am tossing up digging deeper into the math and coding this myself versus using existing code. For whatever reason my school curriculum never included matrices, so I'm filling a gap in my knowledge. Thankfully I only need a few simple things, I think. Context is that I'm programming a robot for the RoboCup 3D league. I'm coding it in C# but it'll have to run on Mono. Ideally I wouldn't use any existing graphics libraries for this (WinForms/WPF/XNA) as all I really need is a neat subset of matrix transformations. Specifically, I need translation and x/y/z rotations, and a way of combining multiple transformations into a single matrix. This will then be applied to my own Vector3 type to produce the transformed Vector3. I've read different advice about this. For example, some model the transformation with a 4x3 matrix, others with a 4x4 matrix. Also, some examples show that you need a forth value for the vector's matrix of 1. What happens to this value when it's included in the output? [1 0 0 0] [x y z 1] * [0 1 0 0] = [a b c d] [0 0 1 0] [2 4 6 1] The parts I'm missing are: What sizes my matrices should be Compositing transformations by multiplying the transformation matrices together Transforming 3D vectors with the resulting matrix As I mostly just want to get this running, any psuedo-code would be great. Information about what matrix values perform what transformations is quite clearly defined on many pages, so need not be discussed here unless you're very keen :)

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• Determine Whether Two Date Ranges Overlap

  - by Ian Nelson

  Given two date ranges, what is the simplest or most efficient way to determine whether the two date ranges overlap? As an example, suppose we have ranges denoted by DateTime variables StartDate1 to EndDate1 and StartDate2 to EndDate2.

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• Is there a way to formerly define a time interval for configuring a process?

  - by gshauger

  Horrible worded question...I know. I'm working on an application that processes data for the previous day. The problem is that I know the customer is going to eventually ask to it for every hour or some other arbitrary time interval. I know that languages such as Java or SQL have masks for defining dates. Well what about a way to define a time interval? Let me ask it this way. If someone asked you to create a configurable piece of software how would you allow the user to specify the time intervals?

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• Code Golf: Rotating Maze

  - by trinithis

  Code Golf: Rotating Maze Make a program that takes in a file consisting of a maze. The maze has walls given by '#'. The maze must include a single ball, given by a 'o' and any number of holes given by a '@'. The maze file can either be entered via command line or read in as a line through standard input. Please specify which in your solution. Your program then does the following: 1: If the ball is not directly above a wall, drop it down to the nearest wall. 2: If the ball passes through a hole during step 1, remove the ball. 3: Display the maze. 4: If there is no ball in the maze, exit. 5: Read a line from the standard input. Given a 1, rotate the maze counterclockwise. Given a 2, rotate the maze clockwise. Rotations are done by 90 degrees. It is up to you to decide if extraneous whitespace is allowed. If the user enters other inputs, repeat this step. 6: Goto step 1. You may assume all input mazes are closed. Note, a hole effectively acts as a wall in this regard. You may assume all input mazes have no extraneous whitespace. The shortest source code by character count wins. Example mazes: ###### #o @# ###### ########### #o # # ####### # ###@ # ######### ########################### # # # # @ # # # # ## # # ####o#### # # # # # # ######### # @ ######################

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• Text message (SMS) verification for signups

  - by Unknown

  I have seen a disturbing trend where websites are starting to require verification sent to cellphones by text message (SMS). Gmail and Facebook are two of them. What I want to know are the following: Is it a good idea to start requiring cellphones instead of emails now? How do I do it on my own website? Edit Here are some of my new questions on the topic in response to the answers: I see that most of you are saying that SMS registrations is ok. But what about the people who don't have cell phones? And why is it accepted to give out your cell phone information freely? Do those big providers really pay per message to a gateway service? Is it not possible to set up a server with the correct SMS software, or at least buy a subscription directly instead of having a middleman?

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• Under what circumstances are linked lists useful?

  - by Jerry Coffin

  Most times I see people try to use linked lists, it seems to me like a poor (or very poor) choice. Perhaps it would be useful to explore the circumstances under which a linked list is or is not a good choice of data structure. Ideally, answers would expound on the criteria to use in selecting a data structure, and which data structures are likely to work best under specified circumstances.

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• why can't a static member be reached through an instance name?

  - by reinier

  say I have: class Test { public static int Hello = 5; } This obviously works: int j = Test.Hello; But why should this not work? Test test = new Test(); int j = test.Hello; The instance could not have a member equally named, so I don't see how this could be ambiguous or unresolvable for a compiler. Anyone any idea why this is?

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