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  • Imlpementations of an Interface with Different Types?

    - by b3njamin
    Searched as best I could but unfortunately I've learned nothing relevant; basically I'm trying to work around the following problem in C#... For example, I have three possible references (refA, refB, refC) and I need to load the correct one depending on a configuration option. So far however I can't see a way of doing it that doesn't require me to use the name of said referenced object all through the code (the referenced objects are provided, I can't change them). Hope the following code makes more sense: public ??? LoadedClass; public Init() { /* load the object, according to which version we need... */ if (Config.Version == "refA") { Namespace.refA LoadedClass = new refA(); } else if (Config.Version == "refB") { Namespace.refB LoadedClass = new refB(); } else if (Config.Version == "refC") { Namespace.refC LoadedClass = new refC(); } Run(); } private void Run(){ { LoadedClass.SomeProperty... LoadedClass.SomeMethod(){ etc... } } As you can see, I need the Loaded class to be public, so in my limited way I'm trying to change the type 'dynamically' as I load in which real class I want. Each of refA, refB and refC will implement the same properties and methods but with different names. Again, this is what I'm working with, not by my design. All that said, I tried to get my head around Interfaces (which sound like they're what I'm after) but I'm looking at them and seeing strict types - which makes sense to me, even if it's not useful to me. Any and all ideas and opinions are welcome and I'll clarify anything if necessary. Excuse any silly mistakes I've made in the terminology, I'm learning all this for the first time. I'm really enjoying working with an OOP language so far though - coming from PHP this stuff is blowing my mind :-)

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  • Starting a code library.

    - by Rob Stevenson-Leggett
    Hi, I've been meaning to start a library of reusable code snippets for a while and never seem to get round to it. I think my main problems are: Where to start. What structure should my library take? Should it be a compiled library (where appropriate or just classes I can drop into any project? Or a library project that can be included? In my experience, a built library will quickly become out of date and the source will get lost. So I'm leaning towards source libraries that I can export from SVN and include in any project. Intellectual property. I am employeed, so a lot of the code I write is not my IP. How can I ensure that I don't give my own IP away using it on projects in work and at home? I'm thinking the best way would be to licence my library with an open source licence and make sure I only add to it in my own time using my own equipment and therefore making sure that if I use it in a work project the same rules apply as if I was using a third party library. I write in many different languages and often would require two or more parts of this library. Should I look at implementing a few template projects and a core project for each of my chosen reusable components and languages? Has anyone else got this sort of library and how do you organise and update it?

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  • How can I make hundreds of simultaneously running processes communicate with a database through one

    - by Olfan
    Long speech short: How can I make hundreds of simultaneously running processes communicate with a database through one or few permanent sessions? The whole story: I once built a number crunching engine that handles vast amounts of large data files by forking off one child after another giving each a small number of files to work on. File locking, progress monitoring and result propagation happen in an Oracle database which all (sub-)processes access at various times using an application-specific module which encapsulates DBI. This worked well at first, but now with higher volumes of input data, the number of database sessions (one per child, and they can be very short-lived) constantly being opened and closed is becoming an issue. I now want to centralise database access so that there are only one or few fixed database sessions which handle all database access for all the (sub-)processes. The presence of the database abstraction module should make the changes easy because the function calls in the worker instances can stay the same. My problem is that I cannot think of a suitable way to enhance said module in order to establish communication between all the processes and the database connector(s). I thought of message queueing, but couldn't come up with a way of connecting a large herd of requestors with one or few database connectors in a way so that bidirectional communication is possible (for collecting the query result). An asynchronous approach could help here in that all requests are written to the same queue and the database connector servicing the request will "call back" to submit the result. But my mind fails me in generating an image clear enough so that I can paint into code. Threading instead of forking might have given me an easier start, but this would now require massive changes to the code base that I'm not prepared to do to a live system. The more I think of it, the more the base idea looks like a pre-forked web server to me only that it doesn't serve web pages but database queries. Any ideas on what to dig into, and where? Sample (pseudo) code to inspire me, links to possibly related articles, ready solutions on CPAN maybe?

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  • need an empty XML while unmarshalling a JAXB annotated class

    - by sswdeveloper
    I have a JAXB annotated class Customer as follows @XmlRootElement(namespace = "http://www.abc.com/customer") public class Customer{ private String name; private Address address; @XmlTransient private HashSet set = new HashSet<String>(); public String getName(){ return name; } @XmlElement(name = "Name", namespace = "http://www.abc.com/customer" ) public void setName(String name){ this.name = name; set.add("name"); } public String getAddress(){ return address; } @XmlElement(name = "Address", namespace = "http://www.abc.com/customer") public void setAddress(Address address){ this.address = address; set.add("address"); } public HashSet getSet(){ return set; } } I need to return an empty XML representing this to the user, so that he may fill the necesary values in the XML and send a request So what I require is : <Customer> <Name></Name> <Address></Address> </Customer> If i simply create an empty object Customer cust = new Customer() ; marshaller.marshall(cust,sw); all I get is the toplevel element since the other fields of the class are unset. What can I do to get such an empty XML? I tried adding the nillable=true annotation to the elements however, this returns me an XML with the xsi:nil="true" which then causes my unmarshaller to ignore this. How do I achieve this?

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  • Prototyping Qt/C++ in Python

    - by tstenner
    I want to write a C++ application with Qt, but build a prototype first using Python and then gradually replace the Python code with C++. Is this the right approach, and what tools (bindings, binding generators, IDE) should I use? Ideally, everything should be available in the Ubuntu repositories so I wouldn't have to worry about incompatible or old versions and have everything set up with a simple aptitude install. Is there any comprehensive documentation about this process or do I have to learn every single component, and if yes, which ones? Right now I have multiple choices to make: Qt Creator, because of the nice auto completion and Qt integration. Eclipse, as it offers support for both C++ and Python. Eric (haven't used it yet) Vim PySide as it's working with CMake and Boost.Python, so theoretically it will make replacing python code easier. PyQt as it's more widely used (more support) and is available as a Debian package. Edit: As I will have to deploy the program to various computers, the C++-solution would require 1-5 files (the program and some library files if I'm linking it statically), using Python I'd have to build PyQt/PySide/SIP/whatever on every platform and explain how to install Python and everything else.

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  • How can I debug PEAR auth?

    - by croceldon
    I have a directory on my site that I've implemented PEAR's Auth to run my authentication. It is working great. However, I've tried to make a copy of my site (it's going to be translated to a different language), and on this new site, the Auth process doesn't seem to be working correctly. I can login properly, but every time I try to go to a different page in the same directory, and use Auth to authorize, it forces me to login again. Here's my logic: $auth_options = array( 'dsn' => mysql://user:password@server/db', 'table' => 'users', 'usernamecol' => 'username', 'passwordcol' => 'password', 'db_fields' => '*' ); $auth = new Auth("DB", $auth_options, "login_function"); $auth->setFailedLoginCallback('bad_login'); $auth->start(); if (!$auth->checkAuth()) { die('cannot succeed in checkAuth') exit; } else { include("nocache.php"); } This is part of a file that's included in every php page I that I desire to require authentication. I can login properly once, but whenever I then try to go to a different page that requires authentication, it makes me login again (and I see the 'cannot succeed' die message at the bottom of the page). Again, this solution works fine on my original site, I copied all the files, and only changed the db server/password - it still doesn't work. And I'm using the same webhost for both. What am I doing wrong here? Or how can I debug this further?

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  • Why doesn't this PHP execute?

    - by cam
    I copied the code from this site exactly: http://davidwalsh.name/web-service-php-mysql-xml-json as follows, /* require the user as the parameter */ if(isset($_GET['user']) && intval($_GET['user'])) { /* soak in the passed variable or set our own */ $number_of_posts = isset($_GET['num']) ? intval($_GET['num']) : 10; //10 is the default $format = strtolower($_GET['format']) == 'json' ? 'json' : 'xml'; //xml is the default $user_id = intval($_GET['user']); //no default /* connect to the db */ $link = mysql_connect('localhost','username','password') or die('Cannot connect to the DB'); mysql_select_db('db_name',$link) or die('Cannot select the DB'); /* grab the posts from the db */ $query = "SELECT post_title, guid FROM wp_posts WHERE post_author = $user_id AND post_status = 'publish' ORDER BY ID DESC LIMIT $number_of_posts"; $result = mysql_query($query,$link) or die('Errant query: '.$query); /* create one master array of the records */ $posts = array(); if(mysql_num_rows($result)) { while($post = mysql_fetch_assoc($result)) { $posts[] = array('post'=>$post); } } /* output in necessary format */ if($format == 'json') { header('Content-type: application/json'); echo json_encode(array('posts'=>$posts)); } else { header('Content-type: text/xml'); echo '<posts>'; foreach($posts as $index => $post) { if(is_array($post)) { foreach($post as $key => $value) { echo '<',$key,'>'; if(is_array($value)) { foreach($value as $tag => $val) { echo '<',$tag,'>',htmlentities($val),'</',$tag,'>'; } } echo '</',$key,'>'; } } } echo '</posts>'; } /* disconnect from the db */ @mysql_close($link); } And the php doesn't execute, it just displays as plain text. What's the dealio? The host supports PHP, I use it to run a Wordpress blog and other things.

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  • Proper API Design for Version Independence?

    - by Justavian
    I've inherited an enormous .NET solution of about 200 projects. There are now some developers who wish to start adding their own components into our application, which will require that we begin exposing functionality via an API. The major problem with that, of course, is that the solution we've got on our hands contains such a spider web of dependencies that we have to be careful to avoid sabotaging the API every time there's a minor change somewhere in the app. We'd also like to be able to incrementally expose new functionality without destroying any previous third party apps. I have a way to solve this problem, but i'm not sure it's the ideal way - i was looking for other ideas. My plan would be to essentially have three dlls. APIServer_1_0.dll - this would be the dll with all of the dependencies. APIClient_1_0.dll - this would be the dll our developers would actual refer to. No references to any of the mess in our solution. APISupport_1_0.dll - this would contain the interfaces which would allow the client piece to dynamically load the "server" component and perform whatever functions are required. Both of the above dlls would depend upon this. It would be the only dll that the "client" piece refers to. I initially arrived at this design, because the way in which we do inter process communication between windows services is sort of similar (except that the client talks to the server via named pipes, rather than dynamically loading dlls). While i'm fairly certain i can make this work, i'm curious to know if there are better ways to accomplish the same task.

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  • Turning a series of raw images into movie frames in Android

    - by Nicholas Killewald
    I've got an Android project I'm working on that, ultimately, will require me to create a movie file out of a series of still images taken with a phone's camera. That is to say, I want to be able to take raw image frames and string them together, one by one, into a movie. Audio is not a concern at this stage. Looking over the Android API, it looks like there are calls in it to create movie files, but it seems those are entirely geared around making a live recording from the camera on an immediate basis. While nice, I can't use that for my purposes, as I need to put annotations and other post-production things on the images as they come in before they get fed into a movie (plus, the images come way too slowly to do a live recording). Worse, looking over the Android source, it looks like a non-trivial task to rewire that to do what I want it to do (at least without touching the NDK). Is there any way I can use the API to do something like this? Or alternatively, what would be the best way to go about this, if it's even feasible on cell phone hardware (which seems to keep getting more and more powerful, strangely...)?

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  • no such file to load -- for several gems unpacked in a Rails 2.3.8 app

    - by vincentp
    Hi, I unpacked several gems into the /vendor/gems folder, and I get the same error message for 5 of these gems when I try to start my Rails application. The date-performance one as an example : no such file to load -- date_performance.so /opt/ruby-enterprise-1.8.7-20090928/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:36:in `gem_original_require' /opt/ruby-enterprise-1.8.7-20090928/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:36:in `require' /opt/ruby-enterprise-1.8.7-20090928/lib/ruby/gems/1.8/gems/activesupport-2.3.8/lib/active_support/dependencies.rb:156:in `require' /opt/ruby-enterprise-1.8.7-20090928/lib/ruby/gems/1.8/gems/activesupport-2.3.8/lib/active_support/dependencies.rb:521:in `new_constants_in' /opt/ruby-enterprise-1.8.7-20090928/lib/ruby/gems/1.8/gems/activesupport-2.3.8/lib/active_support/dependencies.rb:156:in `require' /path_to_my_app/vendor/gems/date-performance-0.4.8/lib/date/performance.rb:34 ... Here is the line 34 : require 'date_performance.so' I'm including the gem using the following code : config.gem "date-performance", :lib => "date/performance" The '.so' file is under /path_to_my_app/vendor/gems/date-performance-0.4.8/lib/ Any idea on why things were working while the gems were not unpacked? Do you have any idea about this behavior? I'm using : Rails 2.3.8 REE 1.8.7 gem 1.3.6 Mac OS X Thanks! Vincent

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  • Implementing client callback functionality in WCF

    - by PoweredByOrange
    The project I'm working on is a client-server application with all services written in WCF and the client in WPF. There are cases where the server needs to push information to the client. I initially though about using WCF Duplex Services, but after doing some research online, I figured a lot of people are avoiding it for many reasons. The next thing I thought about was having the client create a host connection, so that the server could use that to make a service call to the client. The problem however, is that the application is deployed over the internet, so that approach requires configuring the firewall to allow incoming traffic and since most of the users are regular users, that might also require configuring the router to allow port forwarding, which again is a hassle for the user. My third option is that in the client, spawns a background thread which makes a call to the GetNotifications() method on server. This method on the server side then, blocks until an actual notification is created, then the thread is notified (using an AutoResetEvent object maybe?) and the information gets sent to the client. The idea is something like this: Client private void InitializeListener() { Task.Factory.StartNew(() => { while (true) { var notification = server.GetNotifications(); // Display the notification. } }, CancellationToken.None, TaskCreationOptions.LongRunning, TaskScheduler.Default); } Server public NotificationObject GetNotifications() { while (true) { notificationEvent.WaitOne(); return someNotificationObject; } } private void NotificationCreated() { // Inform the client of this event. notificationEvent.Set(); } In this case, NotificationCreated() is a callback method called when the server needs to send information to the client. What do you think about this approach? Is this scalable at all?

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  • finding N contiguous zero bits in an integer to the left of the MSB from another

    - by James Morris
    First we find the MSB of the first integer, and then try to find a region of N contiguous zero bits within the second number which is to the left of the MSB from the first integer. Here is the C code for my solution: typedef unsigned int t; unsigned const t_bits = sizeof(t) * CHAR_BIT; _Bool test_fit_within_left_of_msb( unsigned width, t val1, t val2, unsigned* offset_result) { unsigned offbit = 0; unsigned msb = 0; t mask; t b; while(val1 >>= 1) ++msb; while(offbit + width < t_bits - msb) { mask = (((t)1 << width) - 1) << (t_bits - width - offbit); b = val2 & mask; if (!b) { *offset_result = offbit; return true; } if (offbit++) /* this conditional bothers me! */ b <<= offbit - 1; while(b <<= 1) offbit++; } return false; } Aside from faster ways of finding the MSB of the first integer, the commented test for a zero offbit seems a bit extraneous, but necessary to skip the highest bit of type t if it is set. I have also implemented similar algorithms but working to the right of the MSB of the first number, so they don't require this seemingly extra condition. How can I get rid of this extra condition, or even, are there far more optimal solutions?

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  • Dictionaries with more than one key per value in Python

    - by nickname
    I am attempting to create a nice interface to access a data set where each value has several possible keys. For example, suppose that I have both a number and a name for each value in the data set. I want to be able to access each value using either the number OR the name. I have considered several possible implementations: Using two separate dictionaries, one for the data values organized by number, and one for the data values organized by name. Simply assigning two keys to the same value in a dictionary. Creating dictionaries mapping each name to the corresponding number, and vice versa Attempting to create a hash function that maps each name to a number, etc. (related to the above) Creating an object to encapsulate all three pieces of data, then using one key to map dictionary keys to the objects and simply searching the dictionary to map the other key to the object. None of these seem ideal. The first seems ugly and unmaintainable. The second also seems fragile. The third/fourth seem plausible, but seem to require either much manual specification or an overly complex implementation. Finally, the fifth loses constant-time performance for one of the lookups. In C/C++, I believe that I would use pointers to reference the same piece of data from different keys. I know that the problem is rather similar to a database lookup problem by a non-key column, however, I would like (if possible), to maintain the approximate O(1) performance of Python dictionaries. What is the most Pythonic way to achieve this data structure?

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  • How do I add the go language to gitg's list of viewable sources?

    - by Hotei
    Hoping a 'git' guru will help out here. I am just beginning to "git" for the first time and have (among other things :-) ) git and gitg installed from Ubuntu 10.4 / AMD64 distribution (ie. maybe not 'latest' version but not ancient). I am trying to look at the go code I've committed via gitg and in the "tree tab" it says :Cannot display file content as text. However, the "details tab" shows the diffs of the same file just fine. I know gitg's "tree tab" is working because I can use the tree view on *.c / *.html / *.txt etc just fine. Is there a way to tweak gitg into understanding that "*.go" is just text? A little more context: Installed gitg version is 0.0.5 - ie a version behind latest - 0.0.6 - source of which I am looking thru now. I do have a working /usr/share/gtksourceview-2.0/language-specs/ go.lang. It works just fine as highlighter in gedit. It appears that gitg may require displayable files to have a mime type of "text/plain", so I added that to go.lang No joy. gitg still fails on *.go I'm relatively sure the fix is simple, just don't know where to look.

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  • How to store visited states in iterative deepening / depth limited search?

    - by colinfang
    Update: Search for the first solution. for a normal Depth First Search it is simple, just use a hashset bool DFS (currentState) = { if (myHashSet.Contains(currentState)) { return; } else { myHashSet.Add(currentState); } if (IsSolution(currentState) return true; else { for (var nextState in GetNextStates(currentState)) if (DFS(nextState)) return true; } return false; } However, when it becomes depth limited, i cannot simply do this bool DFS (currentState, maxDepth) = { if (maxDepth = 0) return false; if (myHashSet.Contains(currentState)) { return; } else { myHashSet.Add(currentState); } if (IsSolution(currentState) return true; else { for (var nextState in GetNextStates(currentState)) if (DFS(nextState, maxDepth - 1)) return true; } return false; } Because then it is not going to do a complete search (in a sense of always be able to find a solution if there is any) before maxdepth How should I fix it? Would it add more space complexity to the algorithm? Or it just doesn't require to memoize the state at all. Update: for example, a decision tree is the following: A - B - C - D - E - A | F - G (Goal) Starting from state A. and G is a goal state. Clearly there is a solution under depth 3. However, using my implementation under depth 4, if the direction of search happens to be A(0) -> B(1) -> C(2) -> D(3) -> E(4) -> F(5) exceeds depth, then it would do back track to A, however E is visited, it would ignore the check direction A - E - F - G

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  • PageableListView Not rendering my data as required

    - by Robin
    i am working on wicket, where i am supposed to show my data's under <tr> <td>Name</td> <td>Single Player Score</td> <td>Double Player Score</td> <td>Total Score</td> </tr> <tr wicket:id="data"> <td wicket:id="name"></td> <td wicket:id="singlePlayerScore"></td> <td wicket:id="doublePlayerScore"></td> <td wicket:id="totalScore"></td> </tr> My Player model class is as: Player class with attributes singlePlayerScore, doublePlayerScore(), name with getter and setter and also a list data obtained from database. Data from SQLQuery is as; name score gamemode A 200 singlePlayerMode A 100 doublePLayerMode B 400 singlePlayerMode B 300 doublePLayerMode dataList == player.getScoreList(); My PageableListView is as: final PageableListView listView = new PageableListView("data",dataList,10){ @Override protected void populateItem(Item item){ player = (Player)item.getModelObject(); item.add(Label("name",player.getName())); item.add(Label("singlePlayerScore",player.getName())); item.add(Label("doublePlayerScore",player.getName())); item.add(Label("totalScore",String.valueOf(player.getSinglePlayerScore()+player.getDoublePlayerScore()))); } } My Problem is as: What view i get is as: Name single Player Score Double Player Score Total Score A 0 100 100 A 200 0 200 B 0 300 300 B 400 0 400 How do i achieve below view on my webpage? Name single Player Score Double Player Score Total Score A 200 100 300 B 400 300 700 Please help me as to why is this happening? I guess my list has size four that's one reason why as to it is rendering the view? So what can i do to get as require rendering view?

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  • Screenscraping and reverse engineering health based web tool

    - by ArbInv
    Hi There is a publicly available free tool which has been built to help people understand the impact of various risk factors on their health / life expectancy. I am interested in understanding the data that sits behind the tool. To get this out it would require putting in a range of different socio-demographic factors and analyzing the resulting outputs. This would need to be done across many thousand different individual profiles. The tool was probably built on some standard BI platorm. I have no interest in how the tool was built but do want to get to the data within it. The site has a Terms of Use Agreement which includes: Not copying, distribute, adapt, create derivative works of, translate, or otherwise modify the said tool Not decompile, disassemble, reverse assemble, or otherwise reverse engineer the tool. The said institution retains all rights, title and interest in and to the Tool, and any and all modifications thereof, including all copyright, copyright registrations, trade secrets, trademarks, goodwill and confidential and proprietary information related thereto. Would i be in effect breaking the law if i were to point a screen scraping tool which downloaded the data that sits behind the tool in question?? Any advice welcomed? THANKS

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  • calculating the index of an array C#

    - by Kerry G
    I want to display a list of the answers a student entered incorrectly. How do I identify the index of these questions? I am hoping to change the contents of a textbox to a list of the questions answered incorrectly, which would require calculating the index of each incorrect question. using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Threading.Tasks; using System.Windows.Forms; namespace WindowsFormsApplication5 { public partial class Form1 : Form { public Form1() { InitializeComponent(); } //return a pass/fail //return number of correct answers //return number of incorrect answers //return index figures of incorrect values public void examResults () { string[] correctAnswers = {B,D,A,A,C,A,B,A,C,D,B,C,D,A,D,C,C,B,D,A}; string[] studentResults = File.ReadAllLines("studentResults.txt"); var c = correctAnswers.Where((x, i) => x.Equals(studentResults[i])).Count(); if ( c <= 14) passFailBox.Text = "Student has failed the exam"; else passFailBox.Text = "Student has passed the exam"; numberCorrectBox.Text = "Student has answered" + c + "answers correctly"; int f; f= 21-c; numberIncorrectBox.Text = "Student has answered" + f + "answers incorrectly"; } } }

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  • World Economic Crisis. IT prospects

    - by Andrew Florko
    There was alike question in 2008, 2 years passed. Please, share your expectations about IT market and employment in the next year or two (or so far you can predict). IMHO Russia (my native country) fully met Crisis in spring, 2008. Stock markets shrank 3(!) times during half a year. Many developers were fired those days but I suppose just because business was shocked and freezed some projects. Developers expected +20% salary growth per year in 2004-2007 (Developer salary in Moscow was about 2-3K$ in early 2008). Then there was 30% (very subjective) salary cut-off in 2008 and salaries were frozen till 2009. Now things are slowly coming back to 2008. Looking in the future I expect pessimistic scenario and another crash. Our economic depends more and more on oil & gas every year. IT that serves industry will be shrinked because we can't compete to China in real production. Due to high currency board (rubble is strong compared to dollar) we can't rely on offshore programming. Our officials are concerned on innovative economic breakthrough but it's an ordinary budget money assignemtn in practice. I don't believe in innovations either because who require innovations if you have debts and tomorrow is vapor?

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  • Hopping from a C++ to a Perl Unix profile?

    - by rocknroll
    Hi all, I have been a C++,Linux Developer till now and I am adept in this stack. Off late I have been getting opportunities that require Perl,Unix (with knowledge of C++,shell scripting) expertise. Organisations are showing interest even thought I don't have much scripting experience to boast off. The roll is more in a Support,maintenance project involving SQL as well. Off late I am in a fix whether to forgo these offers or not. I don't know the dynamics of an IT organisation and thus on one hand I fear that my C++ experience will be nullified and on the positive side I am getting to work on a new technology stack which will only add to my skill set. I am sure, most of you at some point of time have encountered such dilemmas and would have taken some decision. I want you to share your perspectives on such a scenario where a person is required to change his/her technology stack when changing his/her job. What are the merits and demerits in going with either of the choices? Also I know that C++ isn't going anywhere in the near future. What about perl? I have no clue as to what the future holds for perl developer? Whether there are enough opportunities for a perl developer? I am asking this question here because most of my fellow programmers face this career choice dilemma. Thanks.

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  • public class ImageHandler : IHttpHandler

    - by Ken
    cmd.Parameters.AddWithValue("@id", new system.Guid (imageid)); What using System reference would this require? Here is the handler: using System; using System.Collections.Specialized; using System.Web; using System.Web.Configuration; using System.Web.Security; using System.Globalization; using System.Configuration; using System.Data.SqlClient; using System.Data; using System.IO; using System.Web.Profile; using System.Drawing; public class ImageHandler : IHttpHandler { public void ProcessRequest(HttpContext context) { string imageid; if (context.Request.QueryString["id"] != null) imageid = (context.Request.QueryString["id"]); else throw new ArgumentException("No parameter specified"); context.Response.ContentType = "image/jpeg"; Stream strm = ShowProfileImage(imageid.ToString()); byte[] buffer = new byte[8192]; int byteSeq = strm.Read(buffer, 0, 8192); while (byteSeq > 0) { context.Response.OutputStream.Write(buffer, 0, byteSeq); byteSeq = strm.Read(buffer, 0, 8192); } //context.Response.BinaryWrite(buffer); } public Stream ShowProfileImage(String imageid) { string conn = ConfigurationManager.ConnectionStrings["MyConnectionString1"].ConnectionString; SqlConnection connection = new SqlConnection(conn); string sql = "SELECT image FROM Profile WHERE UserId = @id"; SqlCommand cmd = new SqlCommand(sql, connection); cmd.CommandType = CommandType.Text; cmd.Parameters.AddWithValue("@id", new system.Guid (imageid));//Failing Here!!!! connection.Open(); object img = cmd.ExecuteScalar(); try { return new MemoryStream((byte[])img); } catch { return null; } finally { connection.Close(); } } public bool IsReusable { get { return false; } } }

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  • what's the performance difference between int and varchar for primary keys

    - by user568576
    I need to create a primary key scheme for a system that will need peer to peer replication. So I'm planning to combine a unique system ID and a sequential number in some way to come up with unique ID's. I want to make sure I'll never run out of ID's, so I'm thinking about using a varchar field, since I could always add another character if I start running out. But I've read that integers are better optimized for this. So I have some questions... 1) Are integers really better optimized? And if they are, how much of a performance difference is there between varchars and integers? I'm going to use firebird for now. But I may switch later. Or possibly support multiple db's. So I'm looking for generalizations, if that's possible. 2) If integers are significantly better optimized, why is that? And is it likely that varchars will catch up in the future, so eventually it won't matter anyway? My varchar keys won't have any meaning, except for the unique system ID part. But I may want to obscure that somehow. Also, I plan to efficiently use all the bits of each character. I don't, for example, plan to code the integer 123 as the character string "123". So I don't think varchars will require more space than integers.

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  • Code Analysis Warning CA1004 with generic method

    - by Vaccano
    I have the following generic method: // Load an object from the disk public static T DeserializeObject<T>(String filename) where T : class { XmlSerializer xmlSerializer = new XmlSerializer(typeof(T)); try { TextReader textReader = new StreamReader(filename); var result = (T)xmlSerializer.Deserialize(textReader); textReader.Close(); return result; } catch (FileNotFoundException) { } return null; } When I compile I get the following warning: CA1004 : Microsoft.Design : Consider a design where 'MiscHelpers.DeserializeObject(string)' doesn't require explicit type parameter 'T' in any call to it. I have considered this and I don't know a way to do what it requests with out limiting the types that can be deserialized. I freely admit that I might be missing an easy way to fix this. But if I am not, then is my only recourse to suppress this warning? I have a clean project with no warnings or messages. I would like to keep it that way. I guess I am asking "why this is a warning?" At best this seems like it should be a message. And even that seems a bit much. Either it can or it can't be fixed. If it can't then you are just stuck with the warning with no recourse but suppressing it. Am I wrong?

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  • Callbacks on GUI Thread

    - by miguel
    We have an external data provider which, in its construtor, takes a callback thread for returning data upon. There are some issues in the system which I am suspicious are related to threading, however, in theory they cannot be, due to the fact that the callbacks should all be returned on the same thread. My question is, does code like this require thread synchronisation? class Foo { ExternalDataProvider _provider; public Foo() { // This is the c'tor for the xternal data provider, taking a callback loop as param _provider = new ExternalDataProvider(UILoop); _provider.DataArrived += ExternalProviderCallbackMethod; } public ExternalProviderCallbackMethod() { var itemArray[] = new String[4] { "item1", "item2", "item3", "item4" }; for (int i = 0; i < itemArray.Length; i++) { string s = itemArray[i]; switch(s) { case "item1": DoItem1Action(); break; case "item2": DoItem2Action(); break; default: DoDefaultAction(); break; } } } } The issue is that, very infrequently, DoItem2Action is executingwhen DoItem1Action should be exectuing. Is it at all possible threading is at fault here? In theory, as all callbacks are arriving on the same thread, they should be serialized, right? So there should be no need for thread sync here?

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  • All Callbacks on GUI Thread - Multithreading issues possible?

    - by miguel
    We have an external data provider which, in its construtor, takes a callback thread for returning data upon. There are some issues in the system which I am suspicious are related to threading, however, in theory they cannot be, due to the fact that the callbacks should all be returned on the same thread. My question is, does code like this require thread synchronisation? class Foo { ExternalDataProvider _provider; public Foo() { // This is the c'tor for the xternal data provider, taking a callback loop as param _provider = new ExternalDataProvider(UILoop); _provider.DataArrived += ExternalProviderCallbackMethod; } public ExternalProviderCallbackMethod(...) { //...(code omitted) var itemArray[] = new String[4] { "item1", "item2", "item3", "item4" }; for (int i = 0; i < itemArray.Length; i++) { string s = itemArray[i]; switch(s) { case "item1": DoItem1Action(); break; case "item2": DoItem2Action(); break; default: DoDefaultAction(); break; } //...(code omitted) } } } The issue is that, very infrequently, DoItem2Action is executingwhen DoItem1Action should be exectuing. Is it at all possible threading is at fault here? In theory, as all callbacks are arriving on the same thread, they should be serialized, right? So there should be no need for thread sync here?

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