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• Database layout tagging system

  - by Kurresmack

  I am creating a web site for a customer and they want to be able to create articles. My idea is to tag them so I am going to implement the system. What is the best design, both from an architectural and a perfomance perspective: 1. To have table with all tags and then have a one to many relationship table that links a tag like this: articles table with ID tags table with ID one to many table with columns Article.ID and Tags.ID 2. To have one table with articles and one with tags for articles like this: articles table with ID tags table with Article.ID and tag text Thanks in advance!

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• Linking Libraries in Xcode

  - by Dan

  Hey all, I'm using a powerbook (osx 10.5) and recently downloaded and installed FFTW 3.2 (link text). I've been able to compile and run some simple programs based on the online tutorial using the terminal: g++ main.cpp -lfftw3 -lm however, I can't get the same program to compile in Xcode. I get a linking error, "symbol(s) not found". There is a file called libfftw3.a in /usr/local/lib. How can this be linked? Furthermore, apparently the libraries have to be linked in a particular order, i.e. see: link text thanks for any help

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• javascript: execute a bunch of asynchronous method with one callback

  - by Samuel Michelot

  I need to execute a bunch of asynchronous methods (client SQLite database), and call only one final callback. Of course, the ugly way is: execAll : function(callBack) { asynch1(function() { asynch2(function() { ... asynchN(function() { callBack(); }) }) }); } But I know there are better ways to do it. Intuitively I would detect when all call back has been called with a counter to call the final callback. I think this is a common design-pattern, so if someone could point me in the right direction... Thanks in advance !

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• Lackadaisical One-to-One between Char and Byte Streams

  - by Vaibhav Bajpai

  I expected to have a one-to-one correspondence between the character streams and byte streams in terms of how the classes are organized in their hierarchy. FilterReader and FilterWriter (character streams) correspond back to FilterInputStream and FilterOutputStream (byte stream) classes. However I noticed few changes as - BufferedInputStream extends FilterInputStream, but BufferedReader does NOT extend FilterReader. BufferedOutputStream and PrintStream both extend FilterOutputStream, but BufferedWriter and PrintWriter does NOT extend FilterWriter. FilterInputStream and FilterOutputStream are not abstract classes, but FilterReader and FilterWriter are. I am not sure if I am being too paranoid to point out such differences, but was just curious to know if there was design reasoning behind such decision.

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• Python os module path functions

  - by broiyan

  From the documentation: os.path.realpath(path) Return the canonical path of the specified filename, eliminating any symbolic links encountered in the path (if they are supported by the operating system). When I invoke this with an extant file's name, I get the path to it: /home/myhome/myproject. When I invoke this with a 'nonsense.xxx' string argument, I still get a path to /home/myhome/myproject/nonsense.xxx. This is a little inconsistent because it looks like nonsense.xxx is taken to be a directory not a file (though it is neither: it does not exist). When I invoke this with a null string file name, I still get a path to /home/myhome/myproject. How can I account for this behaviour when the documentation says so little about realpath()? (I am using Python 2.5.) Edit: Somebody suggested a way to test if files exist. My concern is not to test if files exist. My concern is to account for behaviour.

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• Surrogate key for date dimension?

  - by Navin

  There are 2 school of thoughts : Use surrogate key preferbly in the format of YYYYMMDD as this will always be sequential. Eliminate Date dimension surrogate key and use actual date instead. My Questions to experts on dimension modeling are : 1> Which design would you prefer and why ? 2> How should we handle unknown values in each of the cases, Can we simply place NULL in Fact table for unknown dates as Foreign Key can be NULL (if no why)? 3> If we need to partition fact table on date column ,how would we achieve that in case 1. I am inclined towards using actual date and using NULL to represent UNKNOWN dates in fact table , as date related validation on fact can be done without need to look in to dimension table.

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• Is there such a thing as too many tables?

  - by Stacey

  I've been searching stackoverflow for about an hour now and couldn't find any topics related, so I apologize if this is a duplicate question. My inquery is this. Is there a point at which there are too many tables in a database? Even if the structure is well organized, thought out, and perfectly facilitates the design intent? I have a database that is quickly approaching 40 tables - about 10 main ones, and over 30 ancillary tables (junction tables, 'enumeration' tables, etc). Am I just a bad developer - or should I be trying something different? It seems like so many to me, I'm really afraid at how it will impact the performance of the project. I have done a lot of condensing where possible, grouped similar things where possible, etc. The database is built in MS-SQL 2008.

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• How to use OpenCV in Python?

  - by Roman

  I have just installed OpenCV on my Windows 7 machine. As a result I get a new directory: C:\OpenCV2.2\Python2.7\Lib\site-packages In this directory I have two files: cv.lib and cv.pyd. Then I try to use the opencv from Python. I do the following: import sys sys.path.append('C:\OpenCV2.2\Python2.7\Lib\site-packages') import cv As a result I get the following error message: File "<stdin>", line 1, in <module> ImportError: DLL load failed: The specified module could not be found. What am I doing wrong? ADDED As it was recommended here, I have copied content of C:\OpenCV2.0\Python2.6\Lib\site-packages to the C:\Python26\Lib\site-packages. It did not help.

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• atol(), atof(), atoi() function behaviours, is there a stable way to convert from/to string/integer

  - by Berkay

  In these days i'm playing with the C functions of atol(), atof() and atoi(), from a blog post i find a tutorial and applied: here are my results: void main() char a[10],b[10]; puts("Enter the value of a"); gets(a); puts("Enter the value of b"); gets(b); printf("%s+%s=%ld and %s-%s=%ld",a,b,(atol(a)+atol(b)),a,b,(atol(a)-atol(b))); getch(); } there is atof() which returns the float value of the string and atoi() which returns integer value. now to see the difference between the 3 i checked this code: main() { char a[]={"2545.965"}; printf("atol=%ld\t atof=%f\t atoi=%d\t\n",atol(a),atof(a),atoi(a)); } the output will be atol=2545 atof=2545.965000 atoi=2545 char a[]={“heyyou”}; now when you run the program the following will be the output (why?, is there any solution to convert pure strings to integer?) atol=0 atof=0 atoi=0 the string should contain numeric value now modify this program as char a[]={“007hey”}; the output in this case(tested in Red hat) will be atol=7 atof=7.000000 atoi=7 so the functions has taken 007 only not the remaining part (why?) Now consider this char a[]={“hey007?}; the output of the program will be atol=0 atof=0.000000 atoi=0 So i just want to convert my strings to number and then again to same text, i played with these functions and as you see i'm getting really interesting results? why is that? any other functions to convert from/to string/integer and vice versa?

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• Is there a standard practice for storing default application data?

  - by Rox Wen

  Our application includes a default set of data. The default data includes coefficients and other factors that are unlikely to ever change but still need to be update-able by the user. Currently, the original default data is stored as a populated class within the application. Data updates are stored to an external XML file. This design allows us to include a "reset" feature to restore the original default data. Our rationale for not storing defaults externally [e.g. XML file] was to minimize the risk of being altered. The overall volume of data doesn't warrant a database. Is there a standard practice for storing "default" application data?

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• Using RangeValidator with byte

  - by KevDog

  This is the property declaration in question: [RangeValidator(1,RangeBoundaryType.Inclusive,255,RangeBoundaryType.Inclusive,MessageTemplate = "StartFlexibility is out of range")] public byte StartFlexibility { get; set; } When the validate method is called, a FormatException is thrown telling me that the value type needs to be Int32. How to fix, please?

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• Are there faster XML parsers in Java than Xalan/Xerces

  - by jm04469

  I haven't found many ways to increase the performance of a Java application that does intensive XML processing other than to leverage hardware such as Tarari or Datapower. Does anyone know of any open source ways to accelerate XML parsing?

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• javascript toolkit for offline webapps

  - by anjanb

  hi all, we're building an survey webapp which will let the user to add new records to the survey when offline and will upload when the browser reconnects with the server. We've identified that this will need offline storage and hence google gears seems to be an obvious choice (we understand that adobe Flash has Offline Storage but not sure if that is the best way). I am aware of Dojo offline javascript toolkit which uses google gears for the underlying functionality. However, dojo offline is not part of the dojo toolkit after version 1.3. (currently dojo is 1.4.2). Google gears toolkit is currently frozen except for critical vulnerability fixes (it has not been updated almost for the last 1 yr) because they think that HTML 5 is the way to go ahead. Hence, we're looking for a higher abstraction on top of Google Gears engine TODAY, AND which will (in the future) switch the underlying engine to HTML5 if the browser supports HTML5 standards. We'd love to use Dojo but they have discontinued Dojo offline -- we'd prefer something that will be maintained for some time. Which are possible good strategies, JS toolkits/libraries to use for building this webapp ? Pls. advise.

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• Problem setting up Direct X for C++

  - by Josh

  I've downloaded Direct X SDK from the microsoft website but when I try to compile my code i'm getting this error: Error 1 error LNK2019: unresolved external symbol _Direct3DCreate9@4 referenced in function "void __cdecl initD3D(struct HWND__ *)" (?initD3D@@YAXPAUHWND__@@@Z) C:\Users\Josh\Desktop\Tutorial\Tutorial\Tutorial.obj Tutorial I have added Direct X to my C++ build directories like that: $(DXSDK_DIR)include $(DXSDK_DIR)Lib\x64 I've googled it and found out that most of the time people were forgetting this line: #pragma comment (lib, "d3dx9.lib") But it's there for me here are my includes and lib: #include <windows.h> #include <windowsx.h> #include <d3d9.h> #include <d3dx9.h> #pragma comment (lib, "d3d9.lib") #pragma comment (lib, "d3dx9.lib") Can anyone help me with this? I'm using Visual studio 2010 Professional on win7 x64

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• What are some best practices for making sure your .NET code will scale well?

  - by billmaya

  Last week I interviewed for a position at a TripleA MMORPG game company here in NE. I didn't get the job but one of the areas that came up during the interview was the about the scalability of the code that you write and how it should be considered early on in the design of your architecture and classes. Sadly to say I've never thought very much about the scalability of the .NET code that I've written (I work with single user desktop and mobile applications and our major concerns are usually with device memory and rates of data transmission). I'm interested in learning more about writing code that scales up well so it can handle a wide range of remote users in a client server environment, specifically MMORPGs. Are there any books, web sites, best practices, etc. that could get me started researching this topic?

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• One executable with cmd-line params or just many satellite executables?

  - by Nikos Baxevanis

  I design an application back-end. For now, it is a .NET process (a Console Application) which hosts various communication frameworks such as Agatha and NServiceBus. I need to periodically update my datastore with values (coming from the application while it's running). I found three possible ways: Accept command line arguments, so I can call my console app with -update. On start up a background thread will periodically invoke the update method. Create an updater.exe app which will do the updates, but I will have code duplication since in some way it will need to query the data from the source in order to save it to the datastore. Which one is better?

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• What are the typical reasons Javascript developed on Firefox fails on IE?

  - by karlthorwald

  I developed some javascript enhanced pages that run fine on recent Firefox and Safari. I missed to check in Internet Explorer, and now I find the pages don't work on IE 6 and 7 (so far). The scripts are somehow not executed, the pages show as if javascript wasn't there, although some javascript is executed. I am using own libraries with dom manipulation, from YUI 2 I use YUI-Loader and the XML-Http-Request, and on one page I use "psupload", which depends on JQuery. I am installing Microsoft Script Editor from Office XP and will now debug. I will also write specific tests now. What are the typical failing points of IE? What direction I can keep my eyes open. I found this page, which shows some differences: http://www.quirksmode.org/compatibility.html Can you from your experience name some typical things I should look for first? I will also ask more questions here for specific tasks later, but for now I am interested in your experience why IE usually fails on scripts that run fine in Firefox

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• Wait for tasks to get completed in threadpool.

  - by Alien01

  Hello I have created a thread pool in C++ which stores all tasks in a queue. Thread pool start n number of threads which takes tasks from queue , process each task and then delete tasks from queue. Now , I want to wait till all tasks get completed. Checking for empty queue for completion of tasks may not work as , task can be given to each thread and queue can be emptied but still the tasks can in processing mode. I am not getting idea how to wait for all the tasks completion.This is a design problem. Any suggestions?

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• Merging code with dependencies? - Javascript

  - by RadiantHex

  Hi folks, this might be quite simple, but I must say I'm a bit confused on this topic. I'm writing code based on two popular libraries: jQuery underscore.js I am just wondering what would be the best way to isolate the code and prevent conflicts and how to merge it with its dependencies. By merging I mean putting them within the same file. :) I hope I'm not asking something which is too basic. ...and a last thing MERRY CHRISTMAS EVERYONE! =D

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• Once installed geos library (C++, and C), and then trying to install rgeos package (R), it reports geos-config missing!

  - by user1873888

  Knowing that the package rgeos, from the R language, requieres a prior installation of geos libraries, I installed, both, libgeos and libgeos-c1 (3.2.2), using the synaptic installer in my Ubuntu 12.04 (32 bit) machine. Then I tried to install rgeos directly from the R console, and it issued a message in the sense that geos-config was not found. The output is as follows: > install.packages("rgeos") Installing package(s) into ‘/home/checo/R/i486-pc-linux-gnu-library/2.15’ (as ‘lib’ is unspecified) also installing the dependency ‘sp’ probando la URL 'http://cran.rstudio.com/src/contrib/sp_1.0-9.tar.gz' Content type 'application/x-gzip' length 882102 bytes (861 Kb) URL abierta ================================================== downloaded 861 Kb probando la URL 'http://cran.rstudio.com/src/contrib/rgeos_0.2-19.tar.gz' Content type 'application/x-gzip' length 221471 bytes (216 Kb) URL abierta ================================================== downloaded 216 Kb * installing *source* package ‘sp’ ... ** package ‘sp’ successfully unpacked and MD5 sums checked ** libs gcc -std=gnu99 -I/usr/share/R/include -DNDEBUG -fpic -O3 -pipe -g -c R centroid.c -o Rcentroid.o gcc -std=gnu99 -I/usr/share/R/include -DNDEBUG -fpic -O3 -pipe -g -c gcdist.c -o gcdist.o gcc -std=gnu99 -I/usr/share/R/include -DNDEBUG -fpic -O3 -pipe -g -c init.c -o init.o gcc -std=gnu99 -I/usr/share/R/include -DNDEBUG -fpic -O3 -pipe -g -c pip.c -o pip.o gcc -std=gnu99 -I/usr/share/R/include -DNDEBUG -fpic -O3 -pipe -g -c pip2.c -o pip2.o gcc -std=gnu99 -I/usr/share/R/include -DNDEBUG -fpic -O3 -pipe -g -c sp_xports.c -o sp_xports.o gcc -std=gnu99 -I/usr/share/R/include -DNDEBUG -fpic -O3 -pipe -g -c surfaceArea.c -o surfaceArea.o gcc -std=gnu99 -I/usr/share/R/include -DNDEBUG -fpic -O3 -pipe -g -c zerodist.c -o zerodist.o gcc -std=gnu99 -shared -o sp.so Rcentroid.o gcdist.o init.o pip.o pip2.o sp_xports.o surfaceArea.o zerodist.o -L/usr/lib/R/lib -lR installing to /home/checo/R/i486-pc-linux-gnu-library/2.15/sp/libs ** R ** data ** demo ** inst ** preparing package for lazy loading ** help *** installing help indices ** building package indices ** installing vignettes ‘intro_sp.Rnw’ ‘over.Rnw’ ** testing if installed package can be loaded * DONE (sp) * installing *source* package ‘rgeos’ ... ** package ‘rgeos’ successfully unpacked and MD5 sums checked configure: CC: gcc -std=gnu99 configure: CXX: g++ configure: rgeos: 0.2-17 checking for /usr/bin/svnversion... no configure: svn revision: 394 checking geos-config usability... ./configure: line 1385: geos-config: command not found no configure: error: geos-config not usable ERROR: configuration failed for package ‘rgeos’ * removing ‘/home/checo/R/i486-pc-linux-gnu-library/2.15/rgeos’ Warning in install.packages : installation of package ‘rgeos’ had non-zero exit status Forgive my ignorance, but I don't know where this file, "geos-config", comes from: should it be generated by the gcc compilations above, or should it be previously installed when the libgeos libraries were intalled? I learnt, from another machine, that "geos-config" is an executable and that it should be installed in /usr/bin. Do you have any idea on what's wrong with my procedure? Thanks, -Sergio.

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• Any ideas for developing a Risc Processor friendly string allocator?

  - by Richard Fabian

  I'm working on some tools to enable high throughput data-oriented development, and one thing that I've not got an immediate answer for is how you go about allocating strings quickly. On risc processors you've got another problem of implementation that the CPU doesn't like branching, which is what I'm trying to minimise or avoid. Also, cache coherence is important on most CPUs, so that's gotta be influential in the design too. So, how would you go about reducing the overhead for a generic string allocator? Sometimes it's easier to solve a more explicit problem, so any ideas for string sizes of 5-30?

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• dynamic lib can't find static lib

  - by renyufei

  env: gcc version 4.4.1 (Ubuntu 4.4.1-4ubuntu9) app: Bin(main) calls dynamic lib(testb.so), and testb.so contains a static lib(libtesta.a). file list: main.c test.h a.c b.c then compile as: gcc -o testa.o -c a.c ar -r libtesta.a testa.o gcc -shared -fPIC -o testb.so b.c gcc -o main main.c -L. -ltesta -ldl then compile success, but runs an error: ./main: symbol lookup error: ./testb.so: undefined symbol: print code as follows: test.h #include <stdio.h> #include <stdlib.h> #include <errno.h> #include <string.h> #include <dlfcn.h> int printa(const char *msg); int printb(const char *msg); a.c #include "test.h" int printa(const char *msg) { printf("\tin printa\n"); printf("\t%s\n", msg); } b.c #include "test.h" int printb(const char *msg) { printf("in printb\n"); printa("called by printb\n"); printf("%s\n", msg); } main.c #include "test.h" int main(int argc, char **argv) { void *handle; int (*dfn)(const char *); printf("before dlopen\n"); handle = dlopen("./testb.so", RTLD_LOCAL | RTLD_LAZY); printf("after dlopen\n"); if (handle == NULL) { printf("dlopen fail: [%d][%s][%s]\n", \ errno, strerror(errno), dlerror()); exit(EXIT_FAILURE); } printf("before dlsym\n"); dfn = dlsym(handle, "printb"); printf("after dlsym\n"); if (dfn == NULL) { printf("dlsym fail: [%d][%s][%s]\n", \ errno, strerror(errno), dlerror()); exit(EXIT_FAILURE); } printf("before dfn\n"); dfn("printb func\n"); printf("after dfn\n"); exit(EXIT_SUCCESS); }

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• Top tips for designing GUIs?

  - by oxbow_lakes

  A while back I read (before I lost it) a great book called GUI Bloopers which was full of examples of bad GUI design but also full of useful tidbits like Don't call something a Dialog one minute and a Popup the next. What top tips would you give for designing/documenting a GUI? It would be particularly useful to hear about widgets you designed to cram readable information into as little screen real-estate as possible. I'm going to roll this off with one of my own: avoid trees (e.g. Swing's JTree) unless you really can't avoid it, or have a unbounded hierarchy of stuff. I have found that users don't find them intuitive and they are hard to navigate and filter. PS. I think this question differs from this one as I'm asking for generalist tips

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• creational pattern for instances depending on multiple subclass instances

  - by markusw

  I have a problem, for that I was not able to identify a suitable design pattern. I want to create instances depending on a given type that has been passed to a factory method. What I am doing until now is the following: T create(SuperType x) { if (x instanceof SubType1) { // do some stuff and return a new SubType extends T } else if (x instanceof SubType2) { // do some stuff and return a new SubType extends T } else if ... } else { throw new UnSupportedOperationException("nothing defined for " + x); } } It seems not to be best pratice for me. Has anybody an idea how to solve this in a better way?

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• View artifacts leaking into the model of MVC

  - by Jono

  In an ASP.NET MVC application (which has very little chance of having its view technology ported to something non-HTML, but whose functional requirements evolve weekly,) how much HTML should ideally be allowed to be directly represented in the Model? I might come across as a design bigot for this, but I regard it as bad practice to allow any view constructs to "leak" into the model in an MVC application (and vice versa). For example, a Model that represents an item you're about to purchase should know nothing about the HTML check box that says "add giftwrap/message", nor should it know about any HTML drop down lists for payment card types. Conversely the View shouldn't be doing work like figuring out button text by translating keys into values (by looking in resource files.)

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