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• Interpreters: Handling includes/imports

  - by sub

  I've built an interpreter in C++ and everything works fine so far, but now I'm getting stuck with the design of the import/include/however you want to call it function. I thought about the following: Handling includes in the tokenizing process: When there is an include found in the code, the tokenizing function is recursively called with the filename specified. The tokenized code of the included file is then added to the prior position of the include. Disadvantages: No conditional includes(!) Handling includes during the interpreting process: I don't know how. All I know is that PHP must do it this way as conditional includes are possible. Now my questions: What should I do about includes? How do modern interpreters (Python/Ruby) handle this? Do they allow conditional includes?

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• Very basic database theory.

  - by John R

  I have a set of tables to show the relationship between organziations and supporters below. Although I have done some basic mySQL querries, I know very little about database 'design'. I plan to querry the database for: -a list of contributors to a specific organization... or, -a list of organizations that a specific suporter supports. The database tables for organiations and contributors may have other columns in the future and recieve a lesser amount of querries based on that information. A | X A | Y A | Z B | X B | Y C | X C | Z How should the tables be set up? I assume that there should be a third table, but there is still redundent information in the third table. Is there a better way of setting up the tables? +----+-------+ +-------------+----------+ +----+-------+ | id | org | | org | contr | | id | contr.| +----+-------+ +-------------+----------+ +----+-------+ | 1 | A | | 1 | 1 | | 1 | X | | 2 | B | | 1 | 2 | | 2 | Y | | 3 | C | | 1 | 3 | | 3 | Z | +----+-------+ | 2 | 1 | +----+-------+ | 2 | 2 | | 3 | 1 | | 3 | 3 | +-------------+----------+

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• benefit os having a factory for object creation?

  - by ajsie

  im trying to understand the factory design pattern. i dont understand why it's good to have a middleman between the client and the product (object that the client wants). example with no factory: $mac = new Mac(); example with a factory: $appleStore = new AppleStore(); $mac = $appleStore->getProduct('mac'); how does the factory pattern decouple the client from the product? could someone give an example of a future code change that will impact on example 1 negative, but positive in example 2 so i understand the importance of decoupling? thanks

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• System.NullReferenceException with WhoCanHelpMe Unit Test

  - by tlum

  I'm working with a test project based on WhoCanHelpMe, which is based on Sharp Architecture, NHibernateValidator, etc. As its written the when_the_profile_tasks_is_asked_to_create_a_profile unit test creates the profile object and saves it without issue. Now the profile object is a CreateProfileDetails type that derives from their own ValidatableValueObject which inherits the IValidatable interface. The problem surfaces when my class is based on an Entity rather than their ValidatableValueObject. When the test is run a System.NullReferenceException because Validate() is null. I'm afraid that I'm at a loss to resolve this bad behavior. Does anyone have some suggestions to get to the bottom of this? Thanks, -Ted-

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• Designing Relational Survey Questionnaires Database

  - by user1213055

  I'm trying to build a simple sql database for following access database. Currently there is no relationship and I just have two tables male and female with 6 sections in each form. How can I design it a better way so end user can connect to the database and analyze using STATA or SPSS ? I'm really confused whether I should create one table with all fields or break down into different tables. The database is specific to this study only so I'm not looking for a generic survey database where user can create surveys and capture them. Any feedback or suggestion is much appreciated.

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• Open URL with Safari no matter what system browser is set to

  - by Mark

  In my objective-c program, I need to open a URL in Safari no matter what the system's default browser is. That means that this won't work, because it could launch Firefox or whatever other browser: NSWorkspace * ws = [NSWorkspace sharedWorkspace]; [ws openURL: url]; I think I'm close with this: [ws launchAppWithBundleIdentifier: @"com.apple.Safari" options: NSWorkspaceLaunchWithoutActivation additionalEventParamDescriptor: NULL launchIdentifier: nil]; only need to figure out how to pass in the URL as parameter... Is there an easier way? Thanks!

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• SQL Server concurrency and generated sequence

  - by Goyuix

  I need a sequence of numbers for an application, and I am hoping to leverage the abilities of SQL Server to do it. I have created the following table and procedure (in SQL Server 2005): CREATE TABLE sequences ( seq_name varchar(50) NOT NULL, seq_value int NOT NULL ) CREATE PROCEDURE nextval @seq_name varchar(50) AS BEGIN DECLARE @seq_value INT SET @seq_value = -1 UPDATE sequences SET @seq_value = seq_value = seq_value + 1 WHERE seq_name = @seq_name RETURN @seq_value END I am a little concerned that without locking the table/row another request could happen concurrently and end up returning the same number to another thread or client. This would be very bad obviously. Is this design safe in this regard? Is there something I can add that would add the necessary locking to make it safe? Note: I am aware of IDENTITY inserts in SQL Server - and that is not what I am looking for this in particular case. Specifically, I don't want to be inserting/deleting rows. This is basically to have a central table that manages the sequential number generator for a bunch of sequences.

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• Raising hard limit on RLIMIT_NOFILE system-wide on Linux

  - by jonswar

  We need to raise RLIMIT_NOFILE when running memcached, as we're hitting the default hard limit (1024). However, raising a hard limit requires root, and for various reasons we don't want to have to run memcached or its containing shell as root. Right now we happily run it as a non-root user. Is there a way to raise the hard limit for RLIMIT_NOFILE system-wide, so that we can continue to run memcached as non-root and simply raise the soft limit? This is RedHat Linux with 2.6 kernel. Thanks! Jon

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• Why and How to avoid Event Handler memory leaks ?

  - by gillyb

  Hey There, I just came to realize, by reading some questions and answers on StackOverflow, that adding event handlers using += in C# (or i guess, other .net languages) can cause common memory leaks... I have used event handlers like this in the past many times, and never realized that they can cause, or have caused, memory leaks in my applications. How does this work (meaning, why does this actually cause a memory leak) ? How can I fix this problem ? Is using -= to the same event handler enough ? Are there common design patterns or best practices for handling situations like this ? Example : How am I supposed to handle an application that has many different threads, using many different event handlers to raise several events on the UI ? Are there any good and simple ways to monitor this efficiently in an already built big application ? Thanks in advance!

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• Sequencing ajax requests

  - by Scott Evernden

  I find I sometimes need to iterate some collection and make an ajax call for each element. I want each call to return before moving to the next element so that I don't blast the server with requests - which often leads to other issues. And I don't want to set async to false and freeze the browser. Usually this involves setting up some kind of iterator context that i step thru upon each success callback. I think there must be a cleaner simpler way? Does anyone have a clever design pattern for how to neatly work thru a collection making ajax calls for each item?

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• Javascript points calculating system

  - by coolboycsaba

  I trying to create a points calculating system with javascript, but the problem is with the mathematical part. I have saved on the server the points number, and based on that number I want to decide the level. Sorry for my bad english, I cant explain very well :D. I want something like: level 1 need 0 points level 2 needs 100 points level 3 needs 240 points level 4 needs 420 points level 5 needs 640 points and so on.... I need a mathematical function to calculate each level with it. Something that if I know the level to calculate the points needed, and if I know only the points to calculate the level.

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• What are the differences between struct and class in C++

  - by palm3D

  This question was already asked in the context of C#/.Net. Now I'd like to learn the differences between a struct and a class in (unmanaged) C++. Please discuss the technical differences as well as reasons for choosing one or the other in OO design. I'll start with an obvious difference: If you don't specify public: or private:, members of a struct are public by default; members of a class are private by default. I'm sure there are other differences to be found in the obscure corners of the C++ specification.

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• How should nested components interact with model in a GUI application?

  - by fig-gnuton

  Broad design/architecture question. If you have nested components in a GUI, what's the most common way for those components to interact with data? For example, let's say a component receives a click on one of its buttons to save data. Should the save request be delegated up that component's ancestors, with the uppermost ancestor ultimately passing the request to a controller? Or are models/datastores in a GUI application typically singletons, so that a component at any level of a hierarchy can directly get/set data? Or is a controller injected as a dependency down the hierarchy of components, so that any given component is only one intermediary away from the datastore/model?

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• "Send it to a friend" button on a webpage

  - by kender

  Hey, How often do we see stuff like "Send this page to a friend" on a webpages? Well, I see them quite often. My question is, how do you guys see it's effectiveness? If I hit a webpage that's interesting, and I think my friend would enjoy it, I can just copy the URL from my browser bar, paste it into the email and press "Send" button. In my opinion, it's usually faster and less mistake-aware then the button/link like this on the webpage. In addition, I'm not really sure what this website does with the emails I enter there - don't they store it and then sell for $1/100 addresses to spammers? My question is - when you design a website, do you put such links on the pages (it's often seen on sites with some news/articles)? Does it even make sense?

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• building an XML service parsing library

  - by DanInDC

  This is more of a design question I suppose. My company offers a web service to our client that spits data out in a custom xml format. I'd like to build a java library we can offer so our customers can just feed it the url and we will turn it into a set of POJOs built from the response. I can obviously just create a library that will do some simple xml parsing and building of the POJOs but I'm looking to build something a bit more robust. My brain is pulling me in a million directions, wondering if anyone has some pointers or some code to poke at. Was thinking about adding an Abdera extension, but it's not really a syndication format that fits the Abdera model. And most of the popular service libraries (twitter, facebook) all rely on standards format parsers, of which our format isn't.

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• Capturing Mac OS X System Audio output with Python

  - by richbs

  Hello, I've been trying to "hijack" the Mac OS X system audio using PyAudio and save to a wav in python. That is, I do not want to record from an input device such as a microphone. I want to grab the sound output from any or all applications. I have followed the tutorials on the PyAudio site but these do not appear to cover my use case and when I try to read from the output stream I unsurprisingly get the paCanNotReadFromAnOutputOnlyStream exception. Fair enough! Is there a way to do what I am proposing with the PyAudio or other FOSS Python Library?

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• Adding a comment system to my website

  - by MJ93

  Hey everyone, I'm trying to add some type of comment system to my website for the news that I post on the main page. What I would like it to do is have anybody comment on it (they don't need to login). The comment submission form just required a Name and comment. What would be the simplest way to do this? It would also be nice to have it display how many comments there currently are on the news post. I dont need anything fancy. Thanks!

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• benefit of having a factory for object creation?

  - by ajsie

  I'm trying to understand the factory design pattern. I don't understand why it's good to have a middleman between the client and the product (object that the client wants). example with no factory: $mac = new Mac(); example with a factory: $appleStore = new AppleStore(); $mac = $appleStore->getProduct('mac'); How does the factory pattern decouple the client from the product? Could someone give an example of a future code change that will impact on example 1 negative, but positive in example 2 so I understand the importance of decoupling? Thanks.

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• Where do you find images and graphics designers for your softwares ?

  - by ereOn

  Hi, As a programmer, I'm sure some of you already experienced the same problem: You create a good software (free, open-source, or for friend-only diffusion, whatever) relying on good code and good ideas but since you're a programmer and not an image designer, your program looks just bad. While it seems pretty easy to find motivated developpers to join for free an open-source project, it seems quite hard to find a single free graphic designer. What free and good resources do you usually use for your programs/websites ? Do you have any cool tip that you're willing to share ? Do you know any place where to find people involved into graphic design willing to participate to open-source projects ?

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• How to relate keywords to records - Many to Many

  - by webworm

  Hi All, I am looking for suggestions on database design for a sample jobs listing application. I have many jobs that I would like to associate various keywords with. Each job can have multiple keywords. I would like to store the keywords in a seperate table instead of in a field within the Job table so as to avoid mispellings in keywords. What is the best way to relate keywords to the jobs? I was thinking of using an intermediary table that would have a many to many relationship linking keywords to jobs. Is this the best way to go or should I just have a field in the Job table that contains multiple keywords? Thanks for any suggestions.

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• Return an opaque object to the caller without violating type-safety

  - by JS Bangs

  I have a method which should return a snapshot of the current state, and another method which restores that state. public class MachineModel { public Snapshot CurrentSnapshot { get; } public void RestoreSnapshot (Snapshot saved) { /* etc */ }; } The state Snapshot class should be completely opaque to the caller--no visible methods or properties--but its properties have to be visible within the MachineModel class. I could obviously do this by downcasting, i.e. have CurrentSnapshot return an object, and have RestoreSnapshot accept an object argument which it casts back to a Snapshot. But forced casting like that makes me feel dirty. What's the best alternate design that allows me to be both type-safe and opaque?

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• Drupal and Back-End Complexity

  - by Brian

  Currently I am working on a school website, and we are still in the decision-making process of choosing a framework (we know that we're not using Joomla! or hand-coding). Drupal came up as a viable choice, and currently, that is my best bet for the site. However, I have an issue with CMS's in general. I would like to develop a quite complicated and specifically custom-suited back-end application for teachers to interact with individual students, including the design of shared/custom calendars, announcement privileges, etc. I currently have a bit of expertise with HTML, CSS, PHP, MySQL, and I could wrap my head around some JavaScript and AJAX stuff if need-be. However, would such a complicated application work with Drupal (in that I could create it to specifically suite my purposes)?

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• Why do we need normalized coordinate system? Options

  - by jcyang

  Hi, I have problem understand following sentences in my textbook Computer Graphics with OpenGL. "To make viewing process independent of the requirements of any output device,graphic system convert object descriptions to normalized coordinates and apply the clipping routines." Why normalized coordinates could make viewing process independent of the requirements of any output devices? Isn't the projection coordinates already independent of output device?We only need to first scale and then translate the projection coordinate then we will get device coordinate. So why do we need first convert the projection coordinate to normalized coordinate first? "Clipping is usually performed in normlized coordinates.This allows us to reduce computations by first concatenating the various transformation matrices" Why clipping is usually performed in normlized coordinates? What kind of transformation concatenated? thanks. jcyang.

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• InvalidCastException: System.Web.UI.PartialCachingControl -> MyCustomControl when OutputCaching

  - by marcinn

  The problem: I am unable to use OutputCaching with my controls which derives from MyCustomControl. Controls are loaded dynamically using definitions from database with Page.LoadControl method. When I add to ascx <%@ OutputCache VaryByParam="*" Duration="3600"% the "InvalidCastException: System.Web.UI.PartialCachingControl - MyCustomControl" exception is thrown. I am unable to modify assembly witch contains dynamic loading controls logic. Is there any way to fix it in derived controls? The second question is about iis7 and native output caching - is it resolves this problem? (I tried to set up several performance counters and I saw that cache wasn't hit...)

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• Mistake in dispaly and insert method (double - ended queue)

  - by MANAL

  1) My problem when i make remove from right or left program will be remove true but when i call diplay method the content wrong like this I insert 12 43 65 23 and when make remove from left program will remove 12 but when call display method show like this 12 43 65 and when make remove from right program will remove 23 but when call display method show like this 12 43 Why ?????? ); and when i try to make insert after remove write this Can not insert right because the queue is full . first remove right and then u can insert right where is the problem ?? Please Help me please 2) My code FIRST CLASS class dqueue { private int fullsize; //number of all cells private int item_num; // number of busy cells only private int front,rear; public int j; private double [] dqarr; //========================================== public dqueue(int s) //constructor { fullsize = s; front = 0; rear = -1; item_num = 0; dqarr = new double[fullsize]; } //========================================== public void insert(double data) { if (rear == fullsize-1) rear = -1; rear++; dqarr[rear] = data; item_num++; } public double removeLeft() // take item from front of queue { double temp = dqarr[front++]; // get value and incr front if(front == fullsize) front = 0; item_num --; // one less item return temp; } public double removeRight() // take item from rear of queue { double temp = dqarr[rear--]; // get value and decr rear if(rear == -1) // rear = item_num -1; item_num --; // one less item return temp; } //========================================= public void display () //display items { for (int j=0;j //========================================= public int size() //number of items in queue { return item_num; } //========================================== public boolean isEmpty() // true if queue is empty { return (item_num ==0); } } SECOND CLASS import java.util.Scanner; class dqueuetest { public static void main(String[] args) { Scanner input = new Scanner(System.in); System.out.println(" Welcome here** "); System.out.println(" * Mind Of Programming Group*** "); System.out.println(" _________________________ "); System.out.println("enter size of your dqueue"); int size = input.nextInt(); dqueue mydq = new dqueue(size); System.out.println(""); System.out.println("enter your itemes"); //===================================== for(int i = 0;i<=size-1;i++) { System.out.printf("item %d:",i+1); double item = input.nextDouble(); mydq.insert(item); System.out.println(""); } //===================================== int queue =size ; int c = 0 ; while (c != 6) { System.out.println(""); System.out.println("**************************"); System.out.println(" MAIN MENUE"); System.out.println("1- INSERT RIGHT "); System.out.println("2- REMOVE LEFT"); System.out.println("3- REMOVE RIGHT"); System.out.println("4- DISPLAY"); System.out.println("5- SIZE"); System.out.println("6- EXIT"); System.out.println("**************************"); System.out.println("choose your operation by number(1-6)"); c = input.nextInt(); switch (c) { case 1: if (queue == size) System.out.print("Can not insert right because the queue is full . first remove right and then u can insert right "); else { System.out.print("enter your item: "); double item = input.nextDouble(); mydq.insert(item);} break; case 2: System.out.println("REMOVE FROM REAR :"); if( !mydq.isEmpty() ) { double item = mydq.removeLeft(); System.out.print(item + "\t"); } // end while System.out.println(""); mydq.display(); break; case 3: System.out.println("REMOVE FROM FRONT :"); if( !mydq.isEmpty() ) { double item = mydq.removeRight(); System.out.print(item + "\t"); } // end while System.out.println(""); mydq.display(); break; case 4: System.out.println("The items in Queue are :"); mydq.display(); break; case 5: System.out.println("The Size of the Queue is :"+mydq.size()); break; case 6: System.out.println("Good Bye"); break; default: System.out.println("wrong chiose enter again"); } //end switch } //end while } // end main }//end class

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