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Articles indexed Saturday May 22 2010

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  • How do I become better in math, after being a programmer for several years.

    - by loxs
    I've had quite a weird career till now. First I graduated from a medical school. Then I went into marketing (pharmaceuticals). And then umm, after some time, I decided to go for my (till then) hobby and became a "professional" programmer. I've been quite successful at this ever since. I have quite some languages "under my belt". I earn not bad and I have been involved in the opensource community quite heavily. The thing is that I suck at math :). Well, not totally of course, as I get my work done. But I don't know how much I suck. And I don't know how to find out. Math has never really been of any priority during my middle/high school years. I only picked as little as I could afford, because I was always getting ready to go for Medicine. Of course I know the basics of algebra. Things like "normal" and square equations. Also the basics of geometry. But well, there are things that I have missed. And lately I am being fascinated by things like probability theory, infinity, chaos/order etc. But every time I try to learn something about these topics, I hit a wall of terminology, special symbols, and some special kind of thinking, that is quite like mine (a programmer), but also a lot different (and appears weird to me). So, what kinds of books would you recommend me? It's very hard to find something suitable. All that I find are either too easy (and boring) or totally impenetrable.

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  • Is O_NONBLOCK being set a property of the file descriptor or underlying file?

    - by Daniel Trebbien
    From what I have been reading on The Open Group website on fcntl, open, read, and write, I get the impression that whether O_NONBLOCK is set on a file descriptor, and hence whether non-blocking I/O is used with the descriptor, should be a property of that file descriptor rather than the underlying file. Being a property of the file descriptor means, for example, that if I duplicate a file descriptor or open another descriptor to the same file, then I can use blocking I/O with one and non-blocking I/O with the other. Experimenting with a FIFO, however, it appears that it is not possible to have a blocking I/O descriptor and non-blocking I/O descriptor to the FIFO simultaneously (so whether O_NONBLOCK is set is a property of the underlying file [the FIFO]): #include <errno.h> #include <fcntl.h> #include <stdio.h> #include <stdlib.h> #include <unistd.h> int main(int argc, char **argv) { int fds[2]; if (pipe(fds) == -1) { fprintf(stderr, "`pipe` failed.\n"); return EXIT_FAILURE; } int fd0_dup = dup(fds[0]); if (fd0_dup <= STDERR_FILENO) { fprintf(stderr, "Failed to duplicate the read end\n"); return EXIT_FAILURE; } if (fds[0] == fd0_dup) { fprintf(stderr, "`fds[0]` should not equal `fd0_dup`.\n"); return EXIT_FAILURE; } if ((fcntl(fds[0], F_GETFL) & O_NONBLOCK)) { fprintf(stderr, "`fds[0]` should not have `O_NONBLOCK` set.\n"); return EXIT_FAILURE; } if (fcntl(fd0_dup, F_SETFL, fcntl(fd0_dup, F_GETFL) | O_NONBLOCK) == -1) { fprintf(stderr, "Failed to set `O_NONBLOCK` on `fd0_dup`\n"); return EXIT_FAILURE; } if ((fcntl(fds[0], F_GETFL) & O_NONBLOCK)) { fprintf(stderr, "`fds[0]` should still have `O_NONBLOCK` unset.\n"); return EXIT_FAILURE; // RETURNS HERE } char buf[1]; if (read(fd0_dup, buf, 1) != -1) { fprintf(stderr, "Expected `read` on `fd0_dup` to fail immediately\n"); return EXIT_FAILURE; } else if (errno != EAGAIN) { fprintf(stderr, "Expected `errno` to be `EAGAIN`\n"); return EXIT_FAILURE; } return EXIT_SUCCESS; } This leaves me thinking: is it ever possible to have a non-blocking I/O descriptor and blocking I/O descriptor to the same file and if so, does it depend on the type of file (regular file, FIFO, block special file, character special file, socket, etc.)?

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  • How to get a handle to all JCheckBox objects in order to loop?

    - by EmmyS
    I'm very new to Java and am having some issues looping through JCheckBoxes on a UI. The idea is that I have a bunch of checkboxes (not in a group because more than one can be selected.) When I click a JButton, I want to build a string containing the text from each selected checkbox. The issue I'm having is that our instructor told us that the checkboxes need to be created via a method, which means (see code below) that there isn't a discrete instance name for each checkbox. If there were, I could say something like if(checkBox1.isSelected()) { myString.append(checkBox.getText()); } That would repeat for checkBox2, checkBox3, and so on. But the method provided to us for adding checkboxes to a panel looks like this: public class CheckBoxPanel extends JPanel { private static final long serialVersionUID = 1L; public CheckBoxPanel(String title, String... options) { setBorder(BorderFactory.createTitledBorder(BorderFactory .createEtchedBorder(), title)); setLayout(new BoxLayout(this, BoxLayout.Y_AXIS)); // make one checkbox for each option for (String option : options) { JCheckBox b = new JCheckBox(option); b.setActionCommand(option); add(b); } } } This is called like this: toppingPanel = new CheckBoxPanel("Each Topping $1.50", "Tomato", "Green Pepper", "Black Olives", "Mushrooms", "Extra Cheese", "Pepperoni", "Sausage"); So I now have a panel that contains a border with the title "Each Topping $1.50", and 7 visible checkboxes. What I need to do is get a list of all the selected toppings. We are not supposed to use an ActionListener for each checkbox, but rather get the list when a button is clicked. I'm feeling really clueless here, but I just can't figure out how to get the isSelected property of the checkboxes when the individual checkboxes don't have instance names. Ideally I'd like to somehow add all the checkboxes to an array and loop through the array in the button's action listener to determine which ones are checked, but if I have to check each one individually I will. I just can't figure out how to refer to an individual checkbox when they've been created dynamically.

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  • Install mySQL data using ftp?

    - by Jane
    I am trying to install magento (open source e-commerce platform) sample data on my webhost. I have uploaded the file magento_sample_data.sql via ftp, and setup a new database and have assigned it to a user. How do I get the sample data into my empty database?

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  • How do I escape reserved words used as column names? MySQL/Create Table

    - by acidzombie24
    I am generating tables from classes in .NET and one problem is a class may have a field name key which is a reserved MySQL keyword. How do I escape it in a create table statement? (Note: The other problem below is text must be a fixed size to be indexed/unique) create table if not exists misc_info ( id INTEGER PRIMARY KEY AUTO_INCREMENT NOT NULL, key TEXT UNIQUE NOT NULL, value TEXT NOT NULL)ENGINE=INNODB;

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  • titleForHeaderInSection is not updating Section Header information correctly

    - by Jim
    I have two tableviews where one navigates to the next. Both use more or less the same code and use the managedObjectContext and FetchedResultsController design pattern to provide the relevant data for both tables. My problem happens when I navigate from the first to the second tableview and the data has only one Section Header / Row in the tableview. The data will then not update Section Header information. It does when there is more than one row but not if there is only one row. It leaves the information from the first attempt in place. I can confirm the row data is correct so the relevant data should be being passed to the Section Header correctly but it isn't. Has anyone else come across this problem?

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  • nginx not acknowledging passenger_root option

    - by lowgain
    I'm running a sinatra app on passenger, and trying to hook it to nginx. The relevant part of my config looks like: http { passenger_root /path/to/gem; #this is a valid path passenger_ruby /path/to/ruby; #ditto #etc... server { listen 80; server_name hello.org; root /path/to/stuff/public; passenger_enabled on; } } Whenever I start nginx however, I get: Starting nginx: [alert]: Phusion Passenger is disabled becasue the 'passenger_root' option is not set. Please set this option if you want to enable Phusion Passenger. What am I missing here? Thanks!

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  • Help me choose a desktop: which of these two should I buy?

    - by Sammy
    I just want the more powerful of the two: Choice 1: http://www.bestbuy.com/site/Gateway+-+Desktop+with+AMD+Phenom%26%23153%3B+II+Quad-Core+Processor/9698936.p?id=1218153428687&skuId=9698936 Choice 2: /site/HP+-+Pavilion+Desktop+with+AMD+Phenom%26%23153%3B+II+Quad-Core+Processor/9694506.p?id=1218150609828&skuId=9694506 I can't post more than one hyperlink since I am a new user, so please add bestbuy domain name before choice 2. The latter choice is a bit more expensive but not by much so I don't care about that. As for what I intend to use my machine for, just regular web surfing, light gaming, web development related work, etc. But that doesn't really matter, of these two I just want to know which is the better more powerful system and which you would buy if you were in my position.

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  • A consistent and simple group of IDE and tools for embedded code and unit test in C++ ?

    - by TridenT
    I’m starting a new firmware project in C++ for Texas Instrument C283xx and C6xxx targets. The unit tests will not run on the target, but will be compiled with gcc/gcov on a PC with windows (and run as well on PC) with simple metrics for tested code coverage. The whole project will be part of Cruise Control.NET for continuous integrations. My question is: what are the consistent IDE / framework / tools to work together? A/ One of the developers says CodeComposerStudio V3.1 for application and CodeBlocks + CxxUnit for the Unit tests. B/ I’m more attracted with CodeComposerStudio V4 for application, Eclipse CDT (well, as CCS V4) and CppUnit for unit test + MockCpp for mocks. I don’t want the best in class tools for each process, but a global, consistent and easy solution (or group of tools if you prefer).

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  • How do you solve the 15-puzzle with A-Star or Dijkstra's Algorithm?

    - by Sean
    I've read in one of my AI books that popular algorithms (A-Star, Dijkstra) for path-finding in simulation or games is also used to solve the well-known "15-puzzle". Can anyone give me some pointers on how I would reduce the 15-puzzle to a graph of nodes and edges so that I could apply one of these algorithms? If I were to treat each node in the graph as a game state then wouldn't that tree become quite large? Or is that just the way to do it?

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  • How to program simple chat bot AI?

    - by Larsenal
    I want to build a bot that asks someone a few simple questions and branches based on the answer. I realize parsing meaning from the human responses will be challenging, but how do you setup the program to deal with the "state" of the conversation? EDIT: It will be a one-to-one conversation between a human and the bot.

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  • How to build LLVM using GCC 4 on Windows?

    - by Steve314
    I have been able to build LLVM 2.6 (the llvm-2.6.tar.gz package) using MinGW GCC 3.4.5. I haven't tested properly, but it seems to work. The trouble is, I have libraries of my own which don't build using GCC3, but which work fine in GCC4 (template issues). I believe the first official GCC4 version for MinGW is GCC 4.4.0. EDIT Decluttered - everything useful in the "tried this tried that" info is now in the answer. EDIT Most of this question/answer is redundant with LLVM 2.7 - the standard configure, make routine works fine in MinGW with no hacks or workarounds.

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  • Rss feed for game programmer?

    - by simpleblob
    I was browsing this thread, which has good recommendation but a bit too general for me. So, if anyone has a collection of nice game programming feeds,please share them. :) (both general and specific topics are welcome)

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  • Incomplete information card game

    - by binil
    I would like to develop a trick taking card game. The game is between four players, one of which is a human and the other three hands are played by the computer. Where can I read up about developing the AI for such games?

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  • Access DB with SQL Server Front End

    - by uyuni99
    I have an old Access application that has a lot of code in forms and reports. The database is getting too large and I am thinking of moving the back end to SQL Server. My requirements are as follows: The DB needs to be multiuser and the users (3-5) will need to log in over the web I would prefer not to re-write the forms and reports in ASP or some other web front end. When I think about my choices, I see them as: Have an Access ADP front end and allows remote log-in to the server where it is stored. Not sure if it is possible for 2 users to simultaneously log in Distribute an ADP front end to the users, but I am not sure if it is possible to connect to a SQL Server back end over the internet, and the network traffic may be an issue. Any other solution? I appreciate all help. u

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  • Is there some sort of CacheDependency in System.Runtime.Caching?

    - by Venemo
    I heard that .NET 4 has a new caching API. Okay, so the good old System.Web.Caching.Cache (which is, by the way, still there in .NET 4) has the ability to set so-called CacheDependency objects to determine whether a cached item is expired or not. One can also specify custom logic for determining whether a cached item is still useable or not by deriving a custom subclass from CacheDependency. I'm curious, is there a way to provide such a logic in the new API?

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