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  • Combining Code Review with Trust Metrics

    - by DragonFax
    I don't get the chance to partake of it at work. But I love the idea of code review. Especially of online open source code review like Gerrit Code Review. I love what Trust Metrics have done for forums and collective intelligences sites on the internet like stackexchange, reddit, and wikipedia. Would it be possible to combine the two and come up with an open source project management system. Something that ends up being mostly community driven. Perhaps a kind of wikipedia of code for a project. Where submitters become popular/trusted by having lots of patches reviewed favoriably by others, and accepted into the trunk. And popular/trusted submitters get their patchs accepted faster/easier. I'm looking for some opinions on the idea, or perhaps pointers to where its been done before, if thats the case. This might leave the lead maintiner little more to do than: wrangle the direction of the project by fast-tracking or vetoing specific patches. settling disputes when the CI tests break, or fixing it himself. Is design by community worse than design by committee?

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  • Why do some people hate Dart? [closed]

    - by Hassan
    First, I'd like to note that this question is not intended to compare two languages or technologies, but is only asking about criticisms aimed at a language. I've always thought it a good idea to somehow get rid of Javascript. It works, but it's just so messy. I think many will agree with me there. And that's how I interpreted Google's release of Dart. It seems to me like a very good alternative to Javascript. Now, it looks like some are not very happy that Google has released this new language. Take a look at this Wikipedia page to see what I'm talking about. If you don't feel like reading it, I'll tell you now that some seem to think that Dart is similar to Microsoft's VBScript, in that it only works on Microsoft's browsers. This goes against the web's openness. But it's my understanding that Dart can be compiled to Javascript, which will allow it to be run on any modern browser (as the Wikipedia article also states). So my question is: are these criticisms valid? Is there a real fear that Google is trying to control the web's front-end to be more compatible with its browser?

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  • Get to Know a Candidate (6 of 25): Jill Stein&ndash;Green Party

    - by Brian Lanham
    DISCLAIMER: This is not a post about “Romney” or “Obama”. This is not a post for whom I am voting. Information sourced for Wikipedia. Stein is a physician with degrees from Harvard College and Harvard Medical School.  She serves on the boards of Greater Boston Physicians for Social Responsibility and MassVoters for Fair Elections, and has been active with the Massachusetts Coalition for Healthy Communities Jill Stein advocates a "Green New Deal" in which renewable energy jobs would be created to address climate change and environmental issues with the objective of employing "every American willing and able to work". Citing the research of Dr. Phillip Harvey, Professor of Law & Economics at Rutgers University, as evidence of the successful economic effects of the 1930s' New Deal projects, Stein would fund the plan with a 30% reduction in the U.S. military budget, returning US troops home, and increasing taxes on areas such as capital gains, offshore tax havens and multimillion dollar real estate. Stein plans on impacting what she sees as a growing convergence of environmental crises in water, soil, fisheries and forests, through the creation of sustainable infrastructure based in clean renewable energy generation and sustainable communities principles such as increasing intra-city mass transit and inter-city railroads, creating 'complete streets' that safely encourage bike and pedestrian traffic and regional food systems based on sustainable organic agriculture The Green Party of the United States was founded in 1991 as a voluntary association of state green parties. With its founding, the Green Party of the United States became the primary national Green organization in the United States, eclipsing the Greens/Green Party USA, which emphasized non-electoral movement building. The Green Party of the United States of America emphasizes environmentalism, non-hierarchical participatory democracy, social justice, respect for diversity, peace and nonviolence. Their "Ten Key Values," which are described as non-authoritative guiding principles, are as follows: Grassroots democracy Social justice and equal opportunity Ecological wisdom Nonviolence Decentralization Community-based economics Feminism and gender equality Respect for diversity Personal and global responsibility Future focus and sustainability The Green Party does not accept donations from corporations. Thus, the party's platforms and rhetoric critique any corporate influence and control over government, media, and American society at large. Stein has access to 403 electoral votes and is a write-in candidate in GA, IN, and MS Learn more about Jill Stein and Green Party on Wikipedia.

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  • How can rotating release managers improve a project's velocity and stability?

    - by Yannis Rizos
    The Wikipedia article on Parrot VM includes this unreferenced claim: Core committers take turns producing releases in a revolving schedule, where no single committer is responsible for multiple releases in a row. This practice has improved the project's velocity and stability. Parrot's Release Manager role documentation doesn't offer any further insight into the process, and I couldn't find any reference for the claim. My first thoughts were that rotating release managers seems like a good idea, sharing the responsibility between as many people as possible, and having a certain degree of polyphony in releases. Is it, though? Rotating release managers has been proposed for Launchpad, and there were some interesting counterarguments: Release management is something that requires a good understanding of all parts of the code and the authority to make calls under pressure if issues come up during the release itself The less change we can have to the release process the better from an operational perspective Don't really want an engineer to have to learn all this stuff on the job as well as have other things to take care of (regular development responsibilities) Any change of timezones of the releases would need to be approved with the SAs and: I think this would be a great idea (mainly because of my lust for power), but I also think that there should be some way making sure that a release manager doesn't get overwhelmed if something disastrous happens during release week, maybe by have a deputy release manager at the same time (maybe just falling back to Francis or Kiko would be sufficient). The practice doesn't appear to be very common, and the counterarguments seem reasonalbe and convincing. I'm quite confused on how it would improve a project's velocity and stability, is there something I'm missing, or is this just a bad edit on the Wikipedia article? Worth noting that the top voted answer in the related "Is rotating the lead developer a good or bad idea?" question boldly notes: Don't rotate.

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  • Any algorithm to dedicate a set of known resources to a set of known requirements (scheduling)

    - by Saeed Neamati
    I'm developing an application to help school principals in dedicating teachers to classes and courses over the hours of a week (scheduling). The scenario is roughly something like this: User enters the list of teachers and their free times into the system User enters the list of courses for this semester User enters the list of available classes into the system Well, up to here, there is no big deal. Just simple CRUD operations and nothing extraordinary. However, now what makes this system useful is that the application should automatically and based on an algorithm create the semester scheduling. I think you've got the main idea here. For example application should suggest that teacher A should go to class 1 for mathematics, and at the same time teacher B should go to class 2 for physics. This way all of the classes would be dedicated to lessons and teacher times won't overlap each other. Piece a cake for school principal. However, I can't find a good algorithm for this resource dedication. I mean it seems hard to me. Searching Google resulted in articles from different websites, but they are of no help and use to me. For example: http://en.wikipedia.org/wiki/Resource_allocation or http://en.wikipedia.org/wiki/Scheduling_(production_processes) Is there any algorithm out there, or any application or engine which can help me here? Does this requirements have a known name, like for example time scheduling engine? Any help would be appreciated.

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  • Name of the Countdown Numbers round problem - and algorithmic solutions?

    - by Dai
    For the non-Brits in the audience, there's a segment of a daytime game-show where contestants have a set of 6 numbers and a randomly generated target number. They have to reach the target number using any (but not necessarily all) of the 6 numbers using only arithmetic operators. All calculations must result in positive integers. An example: Youtube: Countdown - The Most Extraordinary Numbers Game Ever? A detailed description is given on Wikipedia: Countdown (Game Show) For example: The contentant selects 6 numbers - two large (possibilities include 25, 50, 75, 100) and four small (numbers 1 .. 10, each included twice in the pool). The numbers picked are 75, 50, 2, 3, 8, 7 are given with a target number of 812. One attempt is (75 + 50 - 8) * 7 - (3 * 2) = 813 (This scores 7 points for a solution within 5 of the target) An exact answer would be (50 + 8) * 7 * 2 = 812 (This would have scored 10 points exactly matching the target). Obviously this problem has existed before the advent of TV, but the Wikipedia article doesn't give it a name. I've also saw this game at a primary school I attended where the game was called "Crypto" as an inter-class competition - but searching for it now reveals nothing. I took part in it a few times and my dad wrote an Excel spreadsheet that attempted to brute-force the problem, I don't remember how it worked (only that it didn't work, what with Excel's 65535 row limit), but surely there must be an algorithmic solution for the problem. Maybe there's a solution that works the way human cognition does (e.g. in-parallel to find numbers 'close enough', then taking candidates and performing 'smaller' operations).

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  • Point in Polygon, Ray Method: ending infinite line

    - by user2878528
    Having a bit of trouble with point in polygon collision detection using the ray method i.e. http://en.wikipedia.org/wiki/Point_in_polygon My problem is I need to give an end to the infinite line created. As with this infinite line I always get an even number of intersections and hence an invalid result. i.e. ignore or intersection to the right of the point being checked what I have what I want My current code based of Mecki awesome response for (int side = 0; side < vertices.Length; side++) { // Test if current side intersects with ray. // create infinite line // See: http://en.wikipedia.org/wiki/Linear_equation a = end_point.Y - start_point.Y; b = start_point.X - end_point.X; c = end_point.X * start_point.Y - start_point.X * end_point.Y; //insert points of vector d2 = a * vertices[side].Position.X + b * vertices[side].Position.Y + c; if (side - 1 < 0) d1 = a * vertices[vertices.Length - 1].Position.X + b * vertices[vertices.Length - 1].Position.Y + c; else d1 = a * vertices[side-1].Position.X + b * vertices[side-1].Position.Y + c; // If points have opposite sides, intersections++; if (d1 > 0 && d2 < 0 ) intersections++; if (d1 < 0 && d2 > 0 ) intersections++; } //if intersections odd inside = true if ((intersections % 2) == 1) inside = true; else inside = false;

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  • Language Design: Are languages like Python and CoffeeScript really more comprehensible?

    - by kittensatplay
    The "Verbally Readable !== Quicker Comprehension" argument on http://ryanflorence.com/2011/case-against-coffeescript/ is really potent and interesting. I and I'm sure others would be very interested in evidence arguing against this. There's clear evidence for this and I believe it. People naturally think in images, not words, so we should be designing languages that aren't similar to human language like English, French, whatever. Being "readable" is quicker comprehension. Most articles on Wikipedia are not readable as they are long, boring, dry, sluggish and very very wordy. Because Wikipedia documents a ton of info, it is not especially helpful when compared to sites with more practical, useful and relevant info. Languages like Python and CoffeScript are "verbally readable" in that they are closer to English syntax. Having programmed firstly and mainly in Python, I'm not so sure this is really a good thing. The second interesting argument is that CoffeeScript is an intermediator, a step between two ends, which may increase the chance of bugs. While CoffeeScript has other practical benefits, this question specifically requests evidence showing support for the counter-case of language "readability"

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  • How should I compress a file with multiple bytes that are the same with Huffman coding?

    - by Omega
    On my great quest for compressing/decompressing files with a Java implementation of Huffman coding (http://en.wikipedia.org/wiki/Huffman_coding) for a school assignment, I am now at the point of building a list of prefix codes. Such codes are used when decompressing a file. Basically, the code is made of zeroes and ones, that are used to follow a path in a Huffman tree (left or right) for, ultimately, finding a byte. In this Wikipedia image, to reach the character m the prefix code would be 0111 The idea is that when you compress the file, you will basically convert all the bytes of the file into prefix codes instead (they tend to be smaller than 8 bits, so there's some gain). So every time the character m appears in a file (which in binary is actually 1101101), it will be replaced by 0111 (if we used the tree above). Therefore, 1101101110110111011011101101 becomes 0111011101110111 in the compressed file. I'm okay with that. But what if the following happens: In the file to be compressed there exists only one unique byte, say 1101101. There are 1000 of such byte. Technically, the prefix code of such byte would be... none, because there is no path to follow, right? I mean, there is only one unique byte anyway, so the tree has just one node. Therefore, if the prefix code is none, I would not be able to write the prefix code in the compressed file, because, well, there is nothing to write. Which brings this problem: how would I compress/decompress such file if it is impossible to write a prefix code when compressing? (using Huffman coding, due to the school assignment's rules) This tutorial seems to explain a bit better about prefix codes: http://www.cprogramming.com/tutorial/computersciencetheory/huffman.html but doesn't seem to address this issue either.

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  • Unable to connect to mysql database using tomcat6 on ubuntu

    - by Rakesh
    I am able to deploy the application on my local system.... connecting to the same remote database... however when I deploy the same war file on the ubuntu server I get the following exception javax.servlet.ServletException: Could not connect to wikipedia database... org.wikipedia.miner.service.WikipediaMinerServlet.init(WikipediaMinerServlet.java:81) sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) java.lang.reflect.Method.invoke(Method.java:616) org.apache.catalina.security.SecurityUtil$1.run(SecurityUtil.java:244) java.security.AccessController.doPrivileged(Native Method) javax.security.auth.Subject.doAsPrivileged(Subject.java:537) org.apache.catalina.security.SecurityUtil.execute(SecurityUtil.java:276) org.apache.catalina.security.SecurityUtil.doAsPrivilege(SecurityUtil.java:162) org.apache.catalina.security.SecurityUtil.doAsPrivilege(SecurityUtil.java:115) org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286) org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:845) org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583) org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447) java.lang.Thread.run(Thread.java:636) I have even placed the mysql connector jar under tomcat6 lib direcotry.... Please help

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  • binary protocols v. text protocols

    - by der_grosse
    does anyone have a good definition for what a binary protocol is? and what is a text protocol actually? how do these compare to each other in terms of bits sent on the wire? here's what wikipedia says about binary protocols: A binary protocol is a protocol which is intended or expected to be read by a machine rather than a human being (http://en.wikipedia.org/wiki/Binary_protocol) oh come on! to be more clear, if I have jpg file how would that be sent through a binary protocol and how through a text one? in terms of bits/bytes sent on the wire of course. at the end of the day if you look at a string it is itself an array of bytes so the distinction between the 2 protocols should rest on what actual data is being sent on the wire. in other words, on how the initial data (jpg file) is encoded before being sent. any coments are apprecited, I am trying to get to the essence of things here. salutations!

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  • Method signature Vs function prototype

    - by Maroloccio
    A formal definition of the two? Current Wiki articles denote their different contexts and applications, such as internal type signature "strings" in Java VMs (1) and C/C++ function prototypes informing compilers of upcoming method definitions (2) but... 1) http://en.wikipedia.org/wiki/Type_signature 2) http://en.wikipedia.org/wiki/Function_prototype ... where to look for a definition which clearly and formally distinguished one from the other? There is literature using the words prototype and signature almost interchangeably yet other uses appear strict and consistent, if language-specific. Background: I am writing documentation for a sample compiler written for a University project.

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  • How to implement SAML SSO

    - by A_M
    How is SAML SSO typically implemented? I've read this about using SAML with Google Apps, and the wikipedia entry on SAML. The wikipedia entry talks about responding with forms containing details of the SAMLRequest and SAMLResponse. Does this mean that the user has to physically submit the form in order to proceed with the single sign on? The google entry talks about using redirects, which seems more seemless to me. However, it also talks about using a form for the response which the user must submit (although it does talk about using JavaScript to automatically submit the form). Is this the standard way of doing this? Using redirects and JavaScript for form submission? Does anyone know of any other good resources about how to go about implementing SSO between a Windows Domain and a J2EE web application. The web application is on a separate network/domain. My client wants to use CA Siteminder (with SAML).

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  • Daylight saving time and Timezone best practices

    - by Oded
    I am hoping to make this question and the answers to it the definitive guide to dealing with daylight saving time, in particular for dealing with the actual change overs. If you have anything to add, please do Many systems are dependent on keeping accurate time, the problem is with changes to time due to daylight savings - moving the clock forward or backwards. For instance, one has business rules in an order taking system that depend on the time of the order - if the clock changes, the rules might not be as clear. How should the time of the order be persisted? There is of course an endless number of scenarios - this one is simply an illustrative one. How have you dealt with the daylight saving issue? What assumptions are part of your solution? (looking for context here) As important, if not more so: What did you try that did not work? Why did it not work? I would be interested in programming, OS, data persistence and other pertinent aspects of the issue. General answers are great, but I would also like to see details especially if they are only available on one platform. Summary of answers and other data: (please add yours) Do: Always persist time according to a unified standard that is not affected by daylight savings. GMT and UTC have been mentioned by different people. Include the local time offset (including DST offset) in stored timestamps. Remember that DST offsets are not always an integer number of hours (e.g. Indian Standard Time is UTC+05:30). If using Java, use JodaTime. - http://joda-time.sourceforge.net/ Create a table TZOffsets with three columns: RegionClassId, StartDateTime, and OffsetMinutes (int, in minutes). See answer Check if your DBMS needs to be shutdown during transition. Business rules should always work on civil time. Internally, keep timestamps in something like civil-time-seconds-from-epoch. See answer Only convert to local times at the last possible moment. Don't: Do not use javascript date and time calculations in web apps unless you ABSOLUTELY have to. Testing: When testing make sure you test countries in the Western and Eastern hemispheres, with both DST in progress and not and a country that does not use DST (6 in total). Reference: Olson database, aka Tz_database - ftp://elsie.nci.nih.gov/pub Sources for Time Zone and DST - http://www.twinsun.com/tz/tz-link.htm ISO format (ISO 8601) - http://en.wikipedia.org/wiki/ISO_8601 Mapping between Olson database and Windows TimeZone Ids, from the Unicode Consortium - http://unicode.org/repos/cldr-tmp/trunk/diff/supplemental/windows_tzid.html TimeZone page on WikiPedia - http://en.wikipedia.org/wiki/Tz_database StackOverflow questions tagged dst - http://stackoverflow.com/questions/tagged/dst StackOverflow questions tagged timezone - http://stackoverflow.com/questions/tagged/timezone Other: Lobby your representative to end the abomination that is DST. We can always hope...

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  • Red-Black trees - Erasing a node with two non-leaf children

    - by SalamiArmi
    Hi all, I've been implementing my own version of a red-black tree, mostly basing my algorithms from Wikipedia (http://en.wikipedia.org/wiki/Red-black_tree). Its fairly concise for the most part, but there's one part that I would like clarification on. When erasing a node from the tree that has 2 non-leaf (non-NULL) children, it says to move either side's children into the deletable node, and remove that child. I'm a little confused as to which side to remove from, based on that. Do I pick the side randomly, do I alternate betweek sides, or do I stick to the same side for every future deletion?

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  • Which are the Extreme Programming "core" practices?

    - by MiKo
    Recently, I began reading about agile methodologies and XP in particular. I am a bit confused, though, about what are considered the practices involved in extreme programming. More precisely: Wikipedia reports 12 practices, which I someway believe to be the "classic" ones. Both Kent Beck and Ron Jeffries indicate 13 practices (you can find the links at the bottom of wikipedia page about "Extreme Programming Practices", I cannot post them here since I am new user of Stack Overflow), while this review of Kent Beck's "XP explained" (2nd edition) report more than 20 somewhat different practices. As a complete beginner in the topic (and basically as a complete beginner as a programmer), I would like to be enlightened on the matter. My impression is that I should look at Beck's book, since the second edition has been written after several years of XPerience, but I can find a lot less material based on that.

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  • Variable-byte encoding clarification

    - by Myx
    Hello: I am very new to the world of byte encoding so please excuse me (and by all means, correct me) if I am using/expressing simple concepts in the wrong way. I am trying to understand variable-byte encoding. I have read the Wikipedia article (http://en.wikipedia.org/wiki/Variable-width_encoding) as well as a book chapter from an Information Retrieval textbook. I think I understand how to encode a decimal integer. For example, if I wanted to provide variable-byte encoding for the integer 60, I would have the following result: 1 0 1 1 1 1 0 0 (please let me know if the above is incorrect). If I understand the scheme, then I'm not completely sure how the information is compressed. Is it because usually we would use 32 bits to represent an integer, so that representing 60 would result in 1 1 1 1 0 0 preceded by 26 zeros, thus wasting that space as opposed to representing it with just 8 bits instead? Thank you in advance for the clarifications.

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  • What are the Worst Software Project Failures Ever?

    - by Warren P
    Is there a good list of "worst software project failures ever" in the history of software development? For example in Canada a "gun registry" project spent around two billion dollars. (http://en.wikipedia.org/wiki/Gun_registry). This is of course, insane, even if the final product "sort of worked". I have heard of an FBI Case file system which there have been several attempts to rewrite, all of them so far, failures. There is a book on the subject (Software Runaways). There doesn't seem to be be a software "boondoggle" list or "fiasco" list on Wikipedia that I can see. (Update: Therac-25 would be the 'winner' of this question, except that I was internally thinking more of Software projects that had as their deliverable, mainly software, as opposed to firmware projects like Therac-25, where the hardware and firmware together are capable of killing people. In terms of pure software monetary debacles, which was my intended question, there are several contenders.)

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  • How is schoolbook long division an O(n^2) algorithm?

    - by eSKay
    Premise: This Wikipedia page suggests that the computational complexity of Schoolbook long division is O(n^2). Deduction: Instead of taking "Two n-digit numbers", if I take one n-digit number and one m-digit number, then the complexity would be O(n*m). Contradiction: Suppose you divide 100000000 (n digits) by 1000 (m digits), you get 100000, which takes six steps to arrive at. Now, if you divide 100000000 (n digits) by 10000 (m digits), you get 10000 . Now this takes only five steps. Conclusion: So, it seems that the order of computation should be something like O(n/m). Question: Who is wrong, me or Wikipedia, and where?

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  • Computationally simple Pseudo-Gaussian Distribution with varying mean and standard deviation?

    - by mstksg
    This picture from wikipedia has a nice example of the sort of functions I'd ideally like to generate http://en.wikipedia.org/wiki/File:Normal_Distribution_PDF.svg Right now I'm using the Irwin-Hall Distribution, which is more or less a Polynomial approximation of the Gaussian distribution...basically, you use uniform random number generator and iterate it x times, and take the average. The more iterations, the more like a Gaussian Distribution it is. It's pretty nice; however I'd like to be able to have one where I can vary the mean. For example, let's say I wanted a number between the range 0 and 10, but around 7. Like, the mean (if I repeated this function multiple times) would turn out to be 7, but the actual range is 0-10. Is there one I should look up, or should I work on doing some fancy maths with standard Gaussian Distributions?

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  • Why use Oracle Application Express for web app?

    - by Jack
    Hi all. I believe we're moving to Oracle Apex for future development. I've read about Oracle Apex on wikipedia and it's pro and con. It seem to me the con outweigh the pro but maybe I'm wrong. I get the sense that Oracle Apex is for DBA with little or no programing knowledge to setup a web app quickly sort like MS Access for none programmer. If you have Oracle Apex working experience, can you share your though? From wikipedia's entry, it doesn't seem like you need to know any programming language at all but just the PL/SQL? edit: Is Oracle Apex scalable? Can it handle traffic like Facebook's size? Thank. Jack

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  • Math for a geodesic sphere

    - by Marcelo Cantos
    I'm trying to create a very specific geodesic tessellation, but I can't find anything online about it. It is normal to subdivide the triangles of an icosahedron into triangle patches and project them onto the sphere. However, I noticed an animated GIF on the Wikipedia entry for Geodesic Domes that appears not to follow this scheme. Geodesic spheres generally comprise a mixture of mostly hexagonal triangle patches, with pentagonal patches forming at the vertices of the original icosahedron; in most cases, these pentagons are linked together; that is, following a straight edge from the center of one pentagon leads to the center of another pentagon. In the Wikipedia animation, however, the edge from the center of one pentagon doesn't appear to intersect the center of an adjacent pentagons; instead it intersects the side of the other pentagon. Hopefully the drawing below makes this clear: Where can I go to learn about the math behind this particular geometry? Ideally, I'd like to know of an algorithm for generating such tessellations.

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  • How do I determine which C/C++ compiler to use?

    - by Adam Siddhi
    Greetings, I am trying to figure out which C/C++ compiler to use. I found this list of C/C++ compilers at Wikipedia: http://en.wikipedia.org/wiki/List_of_compilers#C.2FC.2B.2B_compilers I am fairly certain that I want to go with an open source compiler. I feel that if it is open source then it will be a more complete compiler since many programmer perspectives are used to make it better. Please tell me if you disagree. I should mention that I plan on learning C/C++ mainly to program 2D/3D game applications that will be compatible with Windows, Linux, MAC and iPhone operating systems. I am currently using Windows Vista x64 OS. Thanks, Adam

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  • Factorising program not working. Help required.

    - by Ender
    I am working on a factorisation problem using Fermat's Factorization and for small numbers it is working well. I've been able to calculate the factors (getting the answers from Wolfram Alpha) for small numbers, like the one on the Wikipedia page (5959). Just when I thought I had the problem licked I soon realised that my program was not working when it came to larger numbers. The program follows through the examples from the Wikipedia page, printing out the values a, b, a2 and b2; the results printed for large numbers are not correct. I've followed the pseudocode provided on the Wikipedia page, but am struggling to understand where to go next. Along with the Wikipedia page I have been following this guide. Once again, as my Math knowledge is pretty poor I cannot follow what I need to do next. The code I am using so far is as follows: import java.math.BigInteger; /** * * @author AlexT */ public class Fermat { private BigInteger a, b; private BigInteger b2; private static final BigInteger TWO = BigInteger.valueOf(2); public void fermat(BigInteger N) { // floor(sqrt(N)) BigInteger tmp = getIntSqrt(N); // a <- ceil(sqrt(N)) a = tmp.add(BigInteger.ONE); // b2 <- a*a-N b2 = (a.multiply(a)).subtract(N); final int bitLength = N.bitLength(); BigInteger root = BigInteger.ONE.shiftLeft(bitLength / 2); root = root.add(b2.divide(root)).divide(TWO); // while b2 not square root while(!(isSqrt(b2, root))) { // a <- a + 1 a = a.add(BigInteger.ONE); // b2 <- (a * a) - N b2 = (a.multiply(a)).subtract(N); root = root.add(b2.divide(root)).divide(TWO); } b = getIntSqrt(b2); BigInteger a2 = a.pow(2); // Wrong BigInteger sum = (a.subtract(b)).multiply((a.add(b))); //if(sum.compareTo(N) == 0) { System.out.println("A: " + a + "\nB: " + b); System.out.println("A^2: " + a2 + "\nB^2: " + b2); //} } /** * Is the number provided a perfect Square Root? * @param n * @param root * @return */ private static boolean isSqrt(BigInteger n, BigInteger root) { final BigInteger lowerBound = root.pow(2); final BigInteger upperBound = root.add(BigInteger.ONE).pow(2); return lowerBound.compareTo(n) <= 0 && n.compareTo(upperBound) < 0; } public BigInteger getIntSqrt(BigInteger x) { // It returns s where s^2 < x < (s+1)^2 BigInteger s; // final result BigInteger currentRes = BigInteger.valueOf(0); // init value is 0 BigInteger currentSum = BigInteger.valueOf(0); // init value is 0 BigInteger sum = BigInteger.valueOf(0); String xS = x.toString(); // change input x to a string xS int lengthOfxS = xS.length(); int currentTwoBits; int i=0; // index if(lengthOfxS % 2 != 0) {// if odd length, add a dummy bit xS = "0".concat(xS); // add 0 to the front of string xS lengthOfxS++; } while(i < lengthOfxS){ // go through xS two by two, left to right currentTwoBits = Integer.valueOf(xS.substring(i,i+2)); i += 2; // sum = currentSum*100 + currentTwoBits sum = currentSum.multiply(BigInteger.valueOf(100)); sum = sum.add(BigInteger.valueOf(currentTwoBits)); // subtraction loop do { currentSum = sum; // remember the value before subtract // in next 3 lines, we work out // currentRes = sum - 2*currentRes - 1 sum = sum.subtract(currentRes); // currentRes++ currentRes = currentRes.add(BigInteger.valueOf(1)); sum = sum.subtract(currentRes); } while(sum.compareTo(BigInteger.valueOf(0)) >= 0); // the loop stops when sum < 0 // go one step back currentRes = currentRes.subtract(BigInteger.valueOf(1)); currentRes = currentRes.multiply(BigInteger.valueOf(10)); } s = currentRes.divide(BigInteger.valueOf(10)); // go one step back return s; } /** * @param args the command line arguments */ public static void main(String[] args) { Fermat fermat = new Fermat(); //Works //fermat.fermat(new BigInteger("5959")); // Doesn't Work fermat.fermat(new BigInteger("90283")); } } If anyone can help me out with this problem I'll be eternally grateful.

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