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• PHP namespaces and using the \ prefix in declaration

  - by Jason McCreary

  The following throws an error stating Exception can no be redeclared. namespace \NYTD\ReadingListBackend; class Exception extends \Exception { } However, removing the \ prefix in the namespace declaration does not: namespace NYTD\ReadingListBackend; I recently adopted PHP namespaces. My understanding is that namespaces prefixed with \ are a fully qualified name. So why can't I use the prefix in the namespace declaration? I can when referencing (e.g. new \NYTD\ReadingListBackend\Exception). Would appreciate a full explanation as I couldn't find anything in the docs.

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• Time Complexities of recursive algorithms

  - by Peter

  Whenever I see a recursive solution, or I write recursive code for a problem, it is really difficult for me to figure out the time complexity, in most of the cases I just say its exponential? How is it exponential actually? How people say it is 2^n, when it is n!, when it is n^n or n^k. I have some questions in mind, let say find all permutations of a string (O(n!)) find all sequences which sum up to k in an array (exponential, how exactly do I calculate). Find all subsets of size k whose sum is 0 (will k come somewhere in complexity , it should come right?). Can any1 help me how to calculate the exact complexity of such questions, I am able to wrote code for them , but its hard understanding the exact time complexity.

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• Proper way to structure a Sync Framework DAL

  - by Refracted Paladin

  I am creating a WPF app that needs to allow users to work in a temporary disconnected state and I plan to use a Local Database Cache. My question's are about my data access layer. Do you typically create the whole DAL to point at the Cache or both and create a switching mechanism? Is Entity's a good way to go for my DAL against the Cache? I am used to L2S but my understanding is that I can't use that against SQLCE, correct? Thanks! PS: Any good resources out there for using Sync, Linq, and WPF ALL TOGETHER? Tutorials, videos, etc?

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• nodejs response speed and nginx

  - by user1502440

  I'm just started testing nodejs, and wanted to get some help in understanding following behavior: Example #1: var http = require('http'); http.createServer(function(req, res){ res.writeHeader(200, {'Content-Type': 'text/plain'}); res.end('foo'); }).listen(1001, '0.0.0.0'); Example #2: var http = require('http'); http.createServer(function(req, res){ res.writeHeader(200, {'Content-Type': 'text/plain'}); res.write('foo'); res.end('bar'); }).listen(1001, '0.0.0.0'); When testing response time in Chrome: example #1 - 6-10ms example #2 - 200-220ms But, if test both examples through nginx proxy_pass server{ listen 1011; location / { proxy_pass http://127.0.0.1:1001; } } i get this: example #1 - 4-8ms example #2 - 4-8ms I am not an expert on either nodejs or nginx, and asking if someone can explain this? nodejs - v.0.8.1 nginx - v.1.2.2

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• ASP.Net MVC Web App not running

  - by Aidan Host

  Hi, I developed an ASP.Net MVC v1 web application and it ran fine on our server. The client wanted to move to another server, and the site does not run on the new host's server. The new server specs: Windows 2008 ASP.Net Framework v4 ASP.Net MVC 2 (afaik its included with .Net v4) IIS 7.5 (afaik) Error Message: Could not load file or assembly 'System.Web.Mvc, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The system cannot find the file specified. My understanding is that it should be backwards compatible. Is the app really trying to run in ASP.Net MVC v1 when v2 is available? I have already tried deploying the MVC .dlls to the Bin folder, but it did not work. I also tried changing all the system.Web.Mvc Version values (in the web.config for the web app) from 1.0.0.0 to 2.0.0.0, which also did not work. Any assistance will be greatly appreciated.

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• Problem with dependencies in m2eclipse

  - by MH

  Hi, I have a problem with m2eclipse and Nexus. Normally, when you create a new Maven Project in Eclipse, you can select an Archetype like maven-archetype-quickstart from the Nexus Indexer. Unfortunately, the Nexus Indexer doesn't show anything at all. But the worst part about all this is, that the "Add Dependency" menue doesn't work. (For a better understanding: By clicking on the "Dependencies" tab, you can usually click on a button in order to enter a groupId or artifactId. That's the menue what I am talking about. If I enter for example "junit", it shows no search results.) Does anybody know this issue? How could I fix it? Thanks a million in advance for any help.

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• How can I load an MP3 or similar music file for display and analysis in wxWidgets?

  - by Jon Cage

  I'm developing a GUI in wxPython which allows a user to generate sequences of colours for some toys I'm building. Part of the program needs to load an MP3 (and potentially other formats further down the line) and display it to the user. That should be sufficient to get started but later I'd like to add features like identifying beats and some crude frequency analysis. Is there any simple way of loading / understanding an MP3's contents to display a plot of its amplitudes to the screen using wxWidgets? I later intend to port to C++/wxWidgets for speed and to avoid having to distribute wxPython.

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• Best indexing strategy for several varchar columns in Postgres

  - by Corey

  I have a table with 10 columns that need to be searchable (the table itself has about 20 columns). So the user will enter query criteria for at least one of the columns but possibly all ten. All non-empty criteria is then put into an AND condition Suppose the user provided non-empty criteria for column1 and column4 and column8 the query would be: select * from the_table where column1 like '%column1_query%' and column4 like '%column4_query%' and column8 like '%column8_query%' So my question is: am I better off creating 1 index with 10 columns? 10 indexes with 1 column each? Or do I need to find out what sets of columns are queried together frequently and create indexes for them (an index on cols 1,4 and 8 in the case above). If my understanding is correct a single index of 10 columns would only work effectively if all 10 columns are in the condition. Open to any suggestions here, additionally the rowcount of the table is only expected to be around 20-30K rows but I want to make sure any and all searches on the table are fast. Thanks!

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• Multiple-File Template Implementation

  - by Maxpm

  With normal functions, the declaration and definition are often separated across multiple files like so: // Foo.h namespace Foo { void Bar(); } . // Foo.cpp #include "Foo.h" void Foo::Bar() { cout << "Inside function." << endl; } It is my understanding that this cannot be done with templates. The declaration and definition must not be separate because the appropriate form of the template is created "on-demand" when needed. So, how and where are templates typically defined in a multiple-file project like this? My intuition is that it would be in Foo.cpp because that's where the "meat" of functions normally is, but on the other hand it's the header file that's going to be included.

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• C++ memory management of reference types

  - by Russel

  Hello, I'm still a fairly novice programmer and I have a question about c++ memory management with refence types. First of all, my understanding of reference types: A pointer is put on the stack and the actual data that the pointer points to is created and placed on the heap. Standard arrays and user defined classes are refence types. Is this correct? Second, my main question is do c and c++'s memory management mechanisms (malloc, free and new, delete) always handle this properly and free the memory that a class or array is pointing to? Does everything still work if those pointers get reassigned somehow to other objects of the same size/type on the heap? What if a class has a pointer member that points to another object? I am assuming that delete/freeing the class object doesn't free what it's member pointer points to, is that correct? Thanks all! -R

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• Where can I find a deliberately insecure open source web application?

  - by Phil Laliberte

  As a developer, I've learned that I usually gain a better understanding of best/worst practices through experience. The area of web application security isn't really somewhere where my organization can afford to let developers learn through trial and error. So looking for a hands-on approach to knowledge sharing of best practices in web application security, I was thinking that it would be useful to have an open source application that was deliberately built to be insecure in order to help teach junior developers about application security. Does anyone out there know where to find something like this?

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• android: ListView.setAdapter() is causing IllegalStateException. Not sure how to fix it.

  - by Stev0

  I'm trying to populate a listview with the contents of various ListAdapters based upon the results of a switch statement nested in an OnItemClickListener. When clicking the item, the application was force closing, so I ran it through the dev tools and android debugger. Eclipse is showing me the in the main thread that the application has suspended due an IllegalStateException. I have a marginal understanding of what the particular exception indicates, but not sure how to fix it, or what in my code is causing it to be thrown. Code as follows: final ListView lv = (ListView) findViewById(R.id.main_list); final String[] autos = getResources().getStringArray(R.array.auto_array); final ListAdapter la_auto = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_2, autos); And then further down in the portion dealing with the onclicklistener gallery.setOnItemClickListener(new OnItemClickListener() { public void onItemClick(AdapterView parent, View v, int position, long id) { switch(gallery.getSelectedItemPosition()) { case 0: lv.setAdapter(la_auto); break;

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• Help with output generated by this C code using fork()

  - by Seephor

  I am trying to figure out the output for a block of C code using fork() and I am having some problems understanding why it comes out the way it does. I understand that when using fork() it starts another instance of the program in parallel and that the child instance will return 0. Could someone explain step by step the output to the block of code below? Thank you. main() { int status, i; for (i=0; i<2; ++i){ printf("At the top of pass %d\n", i); if (fork() == 0){ printf("this is a child, i=%d\n", i); } else { wait(&status); printf("This is a parent, i=%d\n", i); } } }

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• Python having problems writing/reading and testing in a correct format

  - by Ionut

  I’m trying to make a program that will do the following: check if auth_file exists if yes - read file and try to login using data from that file - if data is wrong - request new data if no - request some data and then create the file and fill it with requested data So far: import json import getpass import os import requests filename = ".auth_data" auth_file = os.path.realpath(filename) url = 'http://example.com/api' headers = {'content-type': 'application/json'} def load_auth_file(): try: f = open(auth_file, "r") auth_data = f.read() r = requests.get(url, auth=auth_data, headers=headers) if r.reason == 'OK': return auth_data else: print "Incorrect login..." req_auth() except IOError: f = file(auth_file, "w") f.write(req_auth()) f.close() def req_auth(): user = str(raw_input('Username: ')) password = getpass.getpass('Password: ') auth_data = (user, password) r = requests.get(url, auth=auth_data, headers=headers) if r.reason == 'OK': return user, password elif r.reason == "FORBIDDEN": print "Incorrect login information..." req_auth() return False I have the following problems(understanding and applying the correct way): I can't find a correct way of storing the returned data from req_auth() to auth_file in a format that can be read and used in load_auth file PS: Of course I'm a beginner in Python and I'm sure I have missed some key elements here :(

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• Java - JPA - Generators - @SequenceGenerator

  - by Yatendra Goel

  I am learning JPA and have confusion in the @SequenceGenerator annotation. Upto my understanding, it automatically assigns a value to numeric identity fields/properties of an entity. Q1. Does this sequence generator make use of the database's increasing numeric value generating capability or generates the number on his own? Q2. If JPA uses database auto increement feauture, then will it work with datastores that don't have auto increement feature? Q3. If JPA generate numeric value on his own, then how the JPA implementation knows which value to generate next? Does it consult with the database first to see what value was stored last so as to generate the value (last + 1). ====================================================================================== Q4. Please also throw some light on sequenceName and allocationSize properties of @SequenceGenerator annotation.

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• C# Design a class with interface?

  - by Haroon

  I am having a bit of trouble understanding how I will design a class. My class will have 3 methods ICollection<Field> GetFields(); //perform validation internally - return back the object T UpdateFields(ICollection<Field> fields); //pass in model object with values on it, set up fields, then pass back all fields ICollection<Field> GetFieldsWithValues(T object); What is the best way to construct/design such a class keeping in mind: 1. The model object I pass in will be one of 3 or 4 tables, however when I call GetFIelds - internally for each object I know what fields will be there i.e. list.add(new Field{name = "id", value = "5"}); list.add(new Field{name = "nameofcompany", value = "super guys"});

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• Perl, creating a hash of hashes.

  - by Mike

  Based on my current understanding of hashes in Perl, I would expect this code to print "hello world." It instead prints nothing. %a=(); %b=(); $b{str} = "hello"; $a{1}=%b; $b=(); $b{str} = "world"; $a{2}=%b; print "$a{1}{str} $a{2}{str}"; I assume that a hash is just like an array, so why can't I make a hash contain another?

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• Ruby on Rails- :symbols, @iVars and "strings" - oh my!

  - by Meltemi

  New to Rails and trying to get my head around when/why to use :symbols, @ivars , "strings" within the framework. I think I understand the differences between them conceptually only one :symbol instance per project one @ivar per instance multiple "strings" - as they are created whenever referenced (?) Feel free to correct me! The main confusion comes from understanding the rules & conventions of what Rails expects - where and WHY? I'm sure there's an "Ah ha!" moment coming but I haven't had it yet...as it seems pretty arbitrary to me (coming from C/Obj-C). -thx

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• identify documents from results of mahout clustering

  - by Tejas

  I am using mahout to cluster text documents indexed using solr. I have used the "text" field in the document to form vectors. Then I used the k-means driver in mahout for clustering and then the clusterdumper utility to dump the results. I am having difficulty in understanding the output results from the dumper. I could see the clusters formed with term vectors in those clusters. But how do I extract the documents from these clusters. I want the result to be the input documents appearing in different clusters.

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• Would the world be a better place if there were only one programming language?

  - by Simon

  Well, perhaps not the world, but would it encourage more-re-use, less replication of basic code, or at least an uplift in what is considered basic code, more time advancing the application science and a greater encouragement to share, a more advanced base of understanding for new programmers, since the language could be taught ubiquitously and patterns of teaching would have emerged which were optimised for students learning etc etc? I think all of those things would make the programming world better and would probably have significant commercial benefit too. This is definitely not a religious debate about which language is best, and is predicated on the notion of some super-being having designed the perfect language to start with, which was improbable, but it strikes me that if, from the beginning, there were only a single programming language we may be further along in terms of the evolution of the software industry and software science. And although it is now impossible, if you buy some or all of these assertions is there an argument for standardising on a single language for the future so we can accelerate our collective progress rather than all of us re-inventing some part of the same wheel and consigning our children to the same fate?

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• YUI and/or jQuery for a new project?

  - by Hortitude

  If I am starting a new project how should I pick between using YUI 2, YUI 3 and jQuery? I know there are a bunch of questions/answers already about can you use them together, but I am trying to figure out what criteria I should be thinking about to make my decision. Are they overlapping? Is one better at GUI and the other better at internals? Do they play well together? My understanding from other questions is that they can live in different namespaces, so they can live together, but that doesn't necessarily mean that it is good to use both. Thanks!

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• Question about domain models & their visibility...

  - by Another SO User

  I was involved in an interesting debate about the visibility of domain models & was wondering if people here have any good guidance. Per my understanding of MDA, we need not expose the domain model throughout the application layers & tiers The reason being that any change to the domain model has an impact in the overall application The wise thing to do would be to expose light-weight object (DTO's) which are a small sub-set of the domain model to abstract the actual model On the flip side, any change to the domain model would mean changing various DTO's throughout the application for the change to be visible, while if we do expose the domain model, then the change is in a single location Hope to see some comments & thoughts about this. Appreciate all the help!

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• Simple explaination of Arraylists

  - by Jeremy

  I'm new to programming and I'm looking for a simple answer to build my foundation of understanding Arrays. I've used google and searched this site. After a bit of trial and error I get how to make and reference Arrays like thing[3] gets you the fourth thing in the thing array(since 0 is the first). which lets me do something like thing[3].getStupidNumber() to get the StupidNumber of the 4th thing in the thing array. Then I get to ArrayLists which seem to have much more utility but I cant make logical sense of them like Arrays. When i search I cant find this or word this correctly and thus far everything else I've learned clicked easily. so say I make an ArrayList thing with 5 things in it. how do i get to the .getStupidNumber() method inside the fourth thing, if possible? I think if I learn this I can learn the rest on my own. Thanks!

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• is there an easy way to convert jquery code to javascript?

  - by davidsleeps

  hopefully the question doesn't sound stupid, but there are lots of examples out there of achieving certain things in javascript/dom using jQuery. Using jQuery is not always an option (or even a want) which can make understanding the examples of javascript solutions written in jQuery hard. Is there an easy way to convert jQuery code to regular javascript? I guess without having to access or understand the jQuery source code... edit (future readers): pretend there is a logical reason why jQuery isn't available! edit (almost 3 years since I asked this): there is no logical reason why jQuery isn't available :P

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• What are some Servlet Container pros and cons for a Solr installation?

  - by danieltalsky

  The SolrInstall wiki page lists seven different server / Servlet Containers compatible with Solr: Tomcat Jetty Resin JBoss WebSphere Weblogic Glassfish I'm sure that "best" is subjective, so I'll just say my criteria are: easiest to set up, best for search performance with a smallish, infrequently-updated dataset, and with the fewest number of gotchas. Jetty and Tomcat both have apt-get solr packages, so they're clearly the frontrunners for some. Jetty is used in the demo install, but there's some notes that Jetty has some difficulties handling Unicode in some cases. Tomcat is a common choice but my understanding is that it's not as lightweight and has a lot of features not needed by Solr. Is it worth considering any of the others? Are there some important pro's and cons I should be aware of?

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