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What version-control system is most trivial to set up and use for toy projects?

- by Norman Ramsey

I teach the third required intro course in a CS department. One of my homework assignments asks students to speed up code they have written for a previous assignment. Factor-of-ten speedups are routine; factors of 100 or 1000 are not unheard of. (For a factor of 1000 speedup you have to have made rookie mistakes with malloc().) Programs are improved by a sequence is small changes. I ask students to record and describe each change and the resulting improvement. While you're improving a program it is also possible to break it. Wouldn't it be nice to back out? You can see where I'm going with this: my students would benefit enormously from version control. But there are some caveats: Our computing environment is locked down. Anything that depends on a central repository is suspect. Our students are incredibly overloaded. Not just classes but jobs, sports, music, you name it. For them to use a new tool it has to be incredibly easy and have obvious benefits. Our students do most work in pairs. Getting bits back and forth between accounts is problematic. Could this problem also be solved by distributed version control? Complexity is the enemy. I know setting up a CVS repository is too baffling---I myself still have trouble because I only do it once a year. I'm told SVN is even harder. Here are my comments on existing systems: I think central version control (CVS or SVN) is ruled out because our students don't have the administrative privileges needed to make a repository that they can share with one other student. (We are stuck with Unix file permissions.) Also, setup on CVS or SVN is too hard. darcs is way easy to set up, but it's not obvious how you share things. darcs send (to send patches by email) seems promising but it's not clear how to set it up. The introductory documentation for git is not for beginners. Like CVS setup, it's something I myself have trouble with. I'm soliciting suggestions for what source-control to use with beginning students. I suspect we can find resources to put a thin veneer over an existing system and to simplify existing documentation. We probably don't have resources to write new documentation. So, what's really easy to setup, commit, revert, and share changes with a partner but does not have to be easy to merge or to work at scale? A key constraint is that programming pairs have to be able to share work with each other and only each other, and pairs change every week. Our infrastructure is Linux, Solaris, and Windows with a netapp filer. I doubt my IT staff wants to create a Unix group for each pair of students. Is there an easier solution I've overlooked? (Thanks for the accepted answer, which beats the others on account of its excellent reference to Git Magic as well as the helpful comments.)

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how to add multiple filters to pagination?

- by ClarkSKent

Hey, I am trying to allow multiple filters to be selected for my pagination script. So in my pagination, when a user clicks the 'marketing' button(link) it queries the database just for the category that = marketing. The same goes for the other 2 filter buttons as seen in the script below. (automotive, sports). The problem is, I want to be able to select multiple filters like only marketing and auomotive or automotive and sports, for example if I click the marketing filter and then the automotive, it would display the categories that equal marketing, and automotive. I have no idea how to accomplish this, so I have come to the experts to help me out. This is the script I am working on (I am very new to PHP and programming in general): <h3>Filter results by:</h3> <a href='pagi_test.php?category=marketing'>marketing</a> <a href='pagi_test.php?category=automotive'>automotive</a> <a href='pagi_test.php?category=sports'>sports</a> <br /> <h3>Results:</h3> <?php //connecting to the database $error = "Could not connect to the database"; mysql_connect('localhost','root','root') or die($error); mysql_select_db('ajax_demo') or die($error); //max displayed per page $per_page = 3; //get start variable $start = $_GET['start']; $category = mysql_real_escape_string($_GET['category']); //count records $record_count = mysql_num_rows(mysql_query("SELECT * FROM explore WHERE category='$category'")); //count max pages $max_pages = $record_count / $per_page; //may come out as decimal if (!$start) $start = 0; //display data $get = mysql_query("SELECT * FROM explore WHERE category='$category' LIMIT $start, $per_page"); ?> <table width="800px"> <?php while ($row = mysql_fetch_assoc($get)) { // get data $id = $row['id']; $site_name = $row['site_name']; $site_description = $row['site_description']; ?> <tr> <td><?php echo $id; ?></td> <td><?php echo $site_name; ?></td> <td><?php echo $site_description; ?></td> </tr> <?php } //setup prev and next variables $prev = $start - $per_page; $next = $start + $per_page; //show prev button if (!($start<=0)) echo "<a href='pagi_test.php?category=$category&start=$prev'>Prev</a> "; //show page numbers //set variable for first page $i=1; for ($x=0;$x<$record_count;$x=$x+$per_page) { if ($start!=$x) echo " <a href='pagi_test.php?category=$category&start=$x'>$i</a> "; else echo " <a href='pagi_test.php?category=$category&start=$x'><b>$i</b></a> "; $i++; } //show next button if (!($start>=$record_count-$per_page)) echo " <a href='pagi_test.php?category=$category&start=$next'>Next</a>"; ?>

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iOS: Interpreted code - where do they draw the line?

- by d7samurai

Apple's iOS developer guidelines state: 3.3.2 — An Application may not itself install or launch other executable code by any means, including without limitation through the use of a plug-in architecture, calling other frameworks, other APIs or otherwise. No interpreted code may be downloaded or used in an Application except for code that is interpreted and run by Apple’s Documented APIs and built-in interpreter(s). Assuming that downloading data - like XML and images (or a game level description), for example - at run-time is allowed (as is my impression), I am wondering where they draw the line between "data" and "code". Picture the scenario of an app that delivers interactive "presentations" to users (like a survey, for instance). Presentations are added continuously to the server and different presentations are made available to different users, so they cannot be part of the initial app download (this is the whole point). They are described in XML format, but being interactive, they might contain conditional branching of this sort (shown in pseudo form to exemplify): <options id="Gender"> <option value="1">Male</option> <option value="2">Female</option> </options> <branches id="Gender"> <branch value="1"> <image src="Man" /> </branch> <branch value="2"> <image src="Woman" /> </branch> </branches> When the presentation is "played" within the app, the above would be presented in two steps. First a selection screen where the user can click on either of the two choices presented ("Male" or "Female"). Next, an image will be [downloaded dynamically] and displayed based on the choice made in the previous step. Now, it's easy to imagine additional tags describing further logic still. For example, a containing tag could be added: <loop count="3"> <options... /> <branches... /> </loop> The result here being that the selection screen / image screen pair would be sequentially presented three times over, of course. Or imagine some description of a level in a game. It's easy to view that as passive "data", but if it includes, say, several doorways that the user can go through and with various triggers, traps and points attached to them etc - isn't that the same as using a script - or, indeed, interpreted code - to describe options and their conditional responses? Assuming that the interpretation engine for this XML data is already present in the app and that such presentations can only be consumed (not created or edited) in the app, how would this fare against Apple's iOS guidelines? Doesn't XML basically constitute a scripting language (couldn't any interpreted programming language simply be described by XML) in this sense? Would it be OK if the proprietary scripting language (ref the XML used above) was strictly sandboxed (how can they tell?) and not given access to the operating system in any way (but able to download content dynamically - and upload results to the authoring server)? Where does the line go?

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Create Views for object properties in model in MVC 3 application?

- by Anders Svensson

I have an Asp.Net MVC 3 application with a database "Consultants", accessed by EF. Now, the Consultant table in the db has a one-to-many relationship to several other tables for CV type information (work experience, etc). So a user should be able to fill in their name etc once, but should be able to add a number of "work experiences", and so on. But these foreign key tables are complex objects in the model, and when creating the Create View I only get the simple properties as editor fields. How do I go about designing the View or Views so that the complex objects can be filled in as well? I picture a View in my mind where the simple properties are simple fields, and then some sort of control where you can click "add work experience", and as many as needed would be added. But how would I do that and still utilize the model binding? In fact, I don't know how to go about it at all. (BTW, Program and Language stand for things like software experience in general, and natural language competence, not programming languages, in case you're wondering about the relationships there). Any ideas greatly appreciated! Here's the Create View created by the add View command by default: @{ ViewBag.Title = "Create"; } <h2>Create</h2> <script src="@Url.Content("~/Scripts/jquery.validate.min.js")" type="text/javascript"></script> <script src="@Url.Content("~/Scripts/jquery.validate.unobtrusive.min.js")" type="text/javascript"></script> @using (Html.BeginForm()) { @Html.ValidationSummary(true) <fieldset> <legend>Consultant</legend> <div class="editor-label"> @Html.LabelFor(model => model.FirstName) </div> <div class="editor-field"> @Html.EditorFor(model => model.FirstName) @Html.ValidationMessageFor(model => model.FirstName) </div> <div class="editor-label"> @Html.LabelFor(model => model.LastName) </div> <div class="editor-field"> @Html.EditorFor(model => model.LastName) @Html.ValidationMessageFor(model => model.LastName) </div> <div class="editor-label"> @Html.LabelFor(model => model.UserName) </div> <div class="editor-field"> @Html.EditorFor(model => model.UserName) @Html.ValidationMessageFor(model => model.UserName) </div> <div class="editor-label"> @Html.LabelFor(model => model.Description) </div> <div class="editor-field"> @Html.EditorFor(model => model.Description) @Html.ValidationMessageFor(model => model.Description) </div> <p> <input type="submit" value="Create" /> </p> </fieldset> } <div> @Html.ActionLink("Back to List", "Index") </div> And here's the EF database diagram:

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How to make a character jump, both on objects and just normal jump.

- by haxerflaxer

Hi, I'm kind of a beginner when it comes to java programming, and I have a project in school where I'm going to create a game much like Icy Tower. And my question is, how am I going to write to make the character stand on the ground and be able to jump up on objects? Here's my code so far: Part one package Sprites; import java.awt.Image; import java.awt.event.KeyEvent; import javax.swing.ImageIcon; public class jumper { private String jump = "oka.png"; private int dx; private int dy; private int x; private int y; private Image image; public jumper() { ImageIcon ii = new ImageIcon(this.getClass().getResource(jump)); image = ii.getImage(); x = 50; y = 100; } public void move() { x += dx; y += dy; } public int getX() { return x; } public int getY() { return y; } public Image getImage() { return image; } public void keyPressed(KeyEvent e) { int key = e.getKeyCode(); if (key == KeyEvent.VK_LEFT) { dx = -5; ImageIcon ii = new ImageIcon(this.getClass().getResource("oki.png")); image = ii.getImage(); } if (key == KeyEvent.VK_RIGHT){ dx = 5; ImageIcon ii = new ImageIcon(this.getClass().getResource("oka.png")); image = ii.getImage(); } if (key == KeyEvent.VK_SPACE) { dy = -5; } if (key == KeyEvent.VK_DOWN) { dy = 5; } } public void keyReleased(KeyEvent e) { int key = e.getKeyCode(); if (key == KeyEvent.VK_LEFT) { dx = 0; } if (key == KeyEvent.VK_RIGHT){ dx = 0; } if (key == KeyEvent.VK_SPACE) { dy = 0; } if (key == KeyEvent.VK_DOWN) { dy = 0; } } } Part two package Sprites; import java.awt.Color; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.Toolkit; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.awt.event.KeyAdapter; import java.awt.event.KeyEvent; import javax.swing.JPanel; import javax.swing.Timer; public class board extends JPanel implements ActionListener { private Timer klocka; private jumper jumper; public board() { addKeyListener(new TAdapter()); setFocusable(true); setBackground(Color.WHITE); setDoubleBuffered(true); jumper = new jumper(); klocka = new Timer(5, this); klocka.start(); } public void paint(Graphics g) { super.paint(g); Graphics2D g2d = (Graphics2D)g; g2d.drawImage(jumper.getImage(), jumper.getX(), jumper.getY(), this); Toolkit.getDefaultToolkit().sync(); g.dispose(); } public void actionPerformed(ActionEvent e) { jumper.move(); repaint(); } private class TAdapter extends KeyAdapter { public void keyReleased(KeyEvent e) { jumper.keyReleased(e); } public void keyPressed(KeyEvent e) { jumper.keyPressed(e); } } } Part three package Sprites; import javax.swing.JFrame; public class RType extends JFrame { public RType() { add(new board()); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); setSize(800, 600); setLocationRelativeTo(null); setTitle("R - type"); setResizable(false); setVisible(true); } public static void main(String[] args) { new RType(); } } I really appreciate all the help I can get!

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How do you make a character jump, both on objects and just normal jump?

- by haxerflaxer

Hi, I'm kind of a beginner when it comes to java programming, and I have a project in school where I'm going to create a game much like Icy Tower. And my question is, how am I going to write to make the character stand on the ground and be able to jump up on objects? Here's my code so far: Part one package Sprites; import java.awt.Image; import java.awt.event.KeyEvent; import javax.swing.ImageIcon; public class jumper { private String jump = "oka.png"; private int dx; private int dy; private int x; private int y; private Image image; public jumper() { ImageIcon ii = new ImageIcon(this.getClass().getResource(jump)); image = ii.getImage(); x = 50; y = 100; } public void move() { x += dx; y += dy; } public int getX() { return x; } public int getY() { return y; } public Image getImage() { return image; } public void keyPressed(KeyEvent e) { int key = e.getKeyCode(); if (key == KeyEvent.VK_LEFT) { dx = -5; ImageIcon ii = new ImageIcon(this.getClass().getResource("oki.png")); image = ii.getImage(); } if (key == KeyEvent.VK_RIGHT){ dx = 5; ImageIcon ii = new ImageIcon(this.getClass().getResource("oka.png")); image = ii.getImage(); } if (key == KeyEvent.VK_SPACE) { dy = -5; } if (key == KeyEvent.VK_DOWN) { dy = 5; } } public void keyReleased(KeyEvent e) { int key = e.getKeyCode(); if (key == KeyEvent.VK_LEFT) { dx = 0; } if (key == KeyEvent.VK_RIGHT){ dx = 0; } if (key == KeyEvent.VK_SPACE) { dy = 0; } if (key == KeyEvent.VK_DOWN) { dy = 0; } } } Part two package Sprites; import java.awt.Color; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.Toolkit; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.awt.event.KeyAdapter; import java.awt.event.KeyEvent; import javax.swing.JPanel; import javax.swing.Timer; public class board extends JPanel implements ActionListener { private Timer klocka; private jumper jumper; public board() { addKeyListener(new TAdapter()); setFocusable(true); setBackground(Color.WHITE); setDoubleBuffered(true); jumper = new jumper(); klocka = new Timer(5, this); klocka.start(); } public void paint(Graphics g) { super.paint(g); Graphics2D g2d = (Graphics2D)g; g2d.drawImage(jumper.getImage(), jumper.getX(), jumper.getY(), this); Toolkit.getDefaultToolkit().sync(); g.dispose(); } public void actionPerformed(ActionEvent e) { jumper.move(); repaint(); } private class TAdapter extends KeyAdapter { public void keyReleased(KeyEvent e) { jumper.keyReleased(e); } public void keyPressed(KeyEvent e) { jumper.keyPressed(e); } } } Part three package Sprites; import javax.swing.JFrame; public class RType extends JFrame { public RType() { add(new board()); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); setSize(800, 600); setLocationRelativeTo(null); setTitle("R - type"); setResizable(false); setVisible(true); } public static void main(String[] args) { new RType(); } } I really appreciate all the help I can get!

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C++ Serial Port Question

- by Pfeffer

Problem: I have a hand held device that scans those graphic color barcodes on all packaging. There is a track device that I can use that will slide the device automatically. This track device functions by taking ascii code through a serial port. I need to get this thing to work in FileMaker on a Mac. So no terminal programs, etc... What I've got so far: I bought a Keyspan USB/Serial adapter. Using a program called ZTerm I was successful in sending commands to the device. Example: "C,7^M^J" I was also able to do the same thing in Terminal using this command: screen /dev/tty.KeySerial1 57600 and then type in the same command above(but when I typed in I just hit Control-M and Control-J for the carriage return and line feed) Now I'm writing a plug-in for FileMaker(in C++ of course). I want to get what I did above happen in C++ so when I install that plug-in in FileMaker I can just call one of those functions and have the whole process take place right there. I'm able to connect to the device, but I can't talk to it. It is not responding to anything. I've tried connecting to the device(successfully) using these: FILE *comport; if ((comport = fopen("/dev/tty.KeySerial1", "w")) == NULL){...} and int fd; fd = open("/dev/tty.KeySerial1", O_RDWR | O_NOCTTY | O_NDELAY); This is what I've tried so far in way of talking to the device: fputs ("C,7^M^J",comport); or fprintf(comport,"C,7^M^J"); or char buffer[] = { 'C' , ',' , '7' , '^' , 'M' , '^' , 'J' }; fwrite (buffer , 1 , sizeof(buffer) , comport ); or fwrite('C,7^M^J', 1, 1, comport); Questions: When I connected to the device from Terminal and using ZTerm, I was able to set my baud rate of 57600. I think that may be why it isn't responding here. But I don't know how to do it here.... Does any one know how to do that? I tried this, but it didn't work: comport->BaudRate = 57600; There are a lot of class solutions out there but they all call these include files like termios.h and stdio.h. I don't have these and, for whatever reason, I can't find them to download. I've downloaded a few examples but there are like 20 files in them and they're all calling other files I can't find(like the ones listed above). Do I need to find these and if so where? I just don't know enough about C++ Is there a website where I can download libraries?? Another solution might be to put those terminal commands in C++. Is there a way to do that? So this has been driving me crazy. I'm not a C++ guy, I only know basic programming concepts. Is anyone out there a C++ expert? I ideally I'd like this to just work using functions I already have, like those fwrite, fputs stuff. Thanks!

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Using CreateSourceQuery in CTP4 Code First

- by Adam Rackis

I'm guessing this is impossible, but I'll throw it out there anyway. Is it possible to use CreateSourceQuery when programming with the EF4 CodeFirst API, in CTP4? I'd like to eagerly load properties attached to a collection of properties, like this: var sourceQuery = this.CurrentInvoice.PropertyInvoices.CreateSourceQuery(); sourceQuery.Include("Property").ToList(); But of course CreateSourceQuery is defined on EntityCollection<T>, whereas CodeFirst uses plain old ICollection (obviously). Is there some way to convert? I've gotten the below to work, but it's not quite what I'm looking for. Anyone know how to go from what's below to what's above (code below is from a class that inherits DbContext)? ObjectSet<Person> OSPeople = base.ObjectContext.CreateObjectSet<Person>(); OSPeople.Include(Pinner => Pinner.Books).ToList(); Thanks! EDIT: here's my version of the solution posted by zeeshanhirani - who's book by the way is amazing! dynamic result; if (invoice.PropertyInvoices is EntityCollection<PropertyInvoice>) result = (invoices.PropertyInvoices as EntityCollection<PropertyInvoice>).CreateSourceQuery().Yadda.Yadda.Yadda else //must be a unit test! result = invoices.PropertyInvoices; return result.ToList(); EDIT2: Ok, I just realized that you can't dispatch extension methods whilst using dynamic. So I guess we're not quite as dynamic as Ruby, but the example above is easily modifiable to comport with this restriction EDIT3: As mentioned in zeeshanhirani's blog post, this only works if (and only if) you have change-enabled proxies, which will get created if all of your properties are declared virtual. Here's another version of what the method might look like to use CreateSourceQuery with POCOs public class Person { public virtual int ID { get; set; } public virtual string FName { get; set; } public virtual string LName { get; set; } public virtual double Weight { get; set; } public virtual ICollection<Book> Books { get; set; } } public class Book { public virtual int ID { get; set; } public virtual string Title { get; set; } public virtual int Pages { get; set; } public virtual int OwnerID { get; set; } public virtual ICollection<Genre> Genres { get; set; } public virtual Person Owner { get; set; } } public class Genre { public virtual int ID { get; set; } public virtual string Name { get; set; } public virtual Genre ParentGenre { get; set; } public virtual ICollection<Book> Books { get; set; } } public class BookContext : DbContext { public void PrimeBooksCollectionToIncludeGenres(Person P) { if (P.Books is EntityCollection<Book>) (P.Books as EntityCollection<Book>).CreateSourceQuery().Include(b => b.Genres).ToList(); }

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What's the fastest lookup algorithm for a pair data structure (i.e, a map)?

- by truncheon

In the following example a std::map structure is filled with 26 values from A - Z (for key) and 0 – 26 for value. The time taken (on my system) to lookup the last entry (10000000 times) is roughly 250 ms for the vector, and 125 ms for the map. (I compiled using release mode, with O3 option turned on for g++ 4.4) But if for some odd reason I wanted better performance than the std::map, what data structures and functions would I need to consider using? I apologize if the answer seems obvious to you, but I haven't had much experience in the performance critical aspects of C++ programming. UPDATE: This example is rather trivial and hides the true complexity of what I'm trying to achieve. My real world project is a simple scripting language that uses a parser, data tree, and interpreter (instead of a VM stack system). I need to use some kind of data structure (perhaps map) to store the variables names created by script programmers. These are likely to be pretty randomly named, so I need a lookup method that can quickly find a particular key within a (probably) fairly large list of names. #include <ctime> #include <map> #include <vector> #include <iostream> struct mystruct { char key; int value; mystruct(char k = 0, int v = 0) : key(k), value(v) { } }; int find(const std::vector<mystruct>& ref, char key) { for (std::vector<mystruct>::const_iterator i = ref.begin(); i != ref.end(); ++i) if (i->key == key) return i->value; return -1; } int main() { std::map<char, int> mymap; std::vector<mystruct> myvec; for (int i = 'a'; i < 'a' + 26; ++i) { mymap[i] = i - 'a'; myvec.push_back(mystruct(i, i - 'a')); } int pre = clock(); for (int i = 0; i < 10000000; ++i) { find(myvec, 'z'); } std::cout << "linear scan: milli " << clock() - pre << "\n"; pre = clock(); for (int i = 0; i < 10000000; ++i) { mymap['z']; } std::cout << "map scan: milli " << clock() - pre << "\n"; return 0; }

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Synchronous communication using NSOperationQueue

- by chip_munks

I am new to Objective C programming. I have created two threads called add and display using the NSInvocationOperation and added it on to the NSOperationQueue. I make the display thread to run first and then run the add thread. The display thread after printing the "Welcome to display" has to wait for the results to print from the add method. So i have set the waitUntilFinished method. Both the Operations are on the same queue. If i use waitUntilFinished for operations on the same queue there may be a situation for deadlock to happen(from apples developer documentation). Is it so? To wait for particular time interval there is a method called waitUntilDate: But if i need to like this wait(min(100,dmax)); let dmax = 20; How to do i wait for these conditions? It would be much helpful if anyone can explain with an example. EDITED: threadss.h ------------ #import <Foundation/Foundation.h> @interface threadss : NSObject { BOOL m_bRunThread; int a,b,c; NSOperationQueue* queue; NSInvocationOperation* operation; NSInvocationOperation* operation1; NSConditionLock* theConditionLock; } -(void)Thread; -(void)add; -(void)display; @end threadss.m ------------ #import "threadss.h" @implementation threadss -(id)init { if (self = [super init]) { queue = [[NSOperationQueue alloc]init]; operation = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(display) object:nil]; operation1 = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(add) object:nil]; theConditionLock = [[NSConditionLock alloc]init]; } return self; } -(void)Thread { m_bRunThread = YES; //[operation addDependency:operation1]; if (m_bRunThread) { [queue addOperation:operation]; } //[operation addDependency:operation1]; [queue addOperation:operation1]; //[self performSelectorOnMainThread:@selector(display) withObject:nil waitUntilDone:YES]; //NSLog(@"I'm going to do the asynchronous communication btwn the threads!!"); //[self add]; //[operation addDependency:self]; sleep(1); [queue release]; [operation release]; //[operation1 release]; } -(void)add { NSLog(@"Going to add a and b!!"); a=1; b=2; c = a + b; NSLog(@"Finished adding!!"); } -(void)display { NSLog(@"Into the display method"); [operation1 waitUntilFinished]; NSLog(@"The Result is:%d",c); } @end main.m ------- #import <Foundation/Foundation.h> #import "threadss.h" int main (int argc, const char * argv[]) { NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init]; threadss* thread = [[threadss alloc]init]; [thread Thread]; [pool drain]; return 0; } This is what i have tried with a sample program. output 2011-06-03 19:40:47.898 threads_NSOperationQueue[3812:1503] Going to add a and b!! 2011-06-03 19:40:47.898 threads_NSOperationQueue[3812:1303] Into the display method 2011-06-03 19:40:47.902 threads_NSOperationQueue[3812:1503] Finished adding!! 2011-06-03 19:40:47.904 threads_NSOperationQueue[3812:1303] The Result is:3 Is the way of invoking the thread is correct. 1.Will there be any deadlock condition? 2.How to do wait(min(100,dmax)) where dmax = 50.

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How to select table column names in a view and pass to controller in rails?

- by zachd1_618

So I am new to Rails, and OO programming in general. I have some grasp of the MVC architecture. My goal is to make a (nearly) completely dynamic plug-and-play plotting web server. I am fairly confused with params, forms, and select helpers. What I want to do is use Rails drop downs to basically pass parameters as strings to my controller, which will use the params to select certain column data from my database and plot it dynamically. I have the latter part of the task working, but I can't seem to pass values from my view to controller. For simplicity's sake, say my database schema looks like this: --------------Plot--------------- |____x____|____y1____|____y2____| | 1 | 1 | 1 | | 2 | 2 | 4 | | 3 | 3 | 9 | | 4 | 4 | 16 | | 5 | 5 | 25 | ... and in my Model, I have dynamic selector scopes that will let me select just certain columns of data: in Plot.rb class Plot < ActiveRecord::Base scope :select_var, lambda {|varname| select(varname)} scope :between_x, lambda {|x1,x2| where("x BETWEEN ? and ?","#{x1}","#{x2}")} So this way, I can call: irb>>@p1 = Plot.select_var(['x','y1']).between_x(1,3) and get in return a class where @p1.x and @p1.y1 are my only attributes, only for values between x=1 to x=4, which I dynamically plot. I want to start off in a view (plot/index), where I can dynamically select which variable names (table column names), and which rows from the database to fetch and plot. The problem is, most select helpers don't seem to work with columns in the database, only rows. So to select columns, I first get an array of column names that exist in my database with a function I wrote. Plots Controller def index d=Plot.first @tags = d.list_vars end So @tags = ['x','y1','y2'] Then in my plot/index.html.erb I try to use a drop down to select wich variables I send back to the controller. index.html.erb <%= select_tag( :variable, options_for_select(@plots.first.list_vars,:name,:multiple=>:true) )%> <%= button_to 'Plot now!', :controller =>"plots/plot_vars", :variable => params[:variable]%> Finally, in the controller again Plots controller ... def plot_vars @plot_data=Plot.select_vars([params[:variable]]) end The problem is everytime I try this (or one of a hundred variations thereof), the params[:variable] is nill. How can I use a drop down to pass a parameter with string variable names to the controller? Sorry its so long, I have been struggling with this for about a month now. :-( I think my biggest problem is that this setup doesn't really match the Rails architecture. I don't have "users" and "articles" as individual entities. I really have a data structure, not a data object. Trying to work with the structure in terms of data object speak is not necessarily the easiest thing to do I think. For background: My actual database has about 250 columns and a couple million rows, and they get changed and modified from time to time. I know I can make the database smarter, but its not worth it on my end. I work at a scientific institute where there are a ton of projects with databases just like this. Each one has a web developer that spends months setting up a web interface and their own janky plotting setups. I want to make this completely dynamic, as a plug-and-play solution so all you have to do is specify your database connection, and this rails setup will automatically show and plot which data you want in it. I am more of a sequential programmer and number cruncher, as are many people here. I think this project could be very helpful in the end, but its difficult to figure out for me right now.

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Android - Resuming application state - SL4A

- by toyotajon93

please dont harpoon me for a noob-ish question. I am working on an android application using SL4A, when my application starts it runs in the background while the script is being executed. I'm not sure where to start but each time I click my icon, it re-starts my application. I have tried using different launchmodes with nothing different happening. I'm thinking it has to do with the OnCreate code, and the setting of the notification. I need help saving my application state and then resuming on either re-click of icon or click from notification bar. I've tried everything had to turn here for help. I am not a pro at android programming by any means. Thanks guys, be gentle ;) Public void onCreate() { super.onCreate(); mInterpreterConfiguration = ((BaseApplication) getApplication()) .getInterpreterConfiguration(); } @Override public void onStart(Intent intent, final int startId) { super.onStart(intent, startId); String fileName = Script.getFileName(this); Interpreter interpreter = mInterpreterConfiguration .getInterpreterForScript(fileName); if (interpreter == null || !interpreter.isInstalled()) { mLatch.countDown(); if (FeaturedInterpreters.isSupported(fileName)) { Intent i = new Intent(this, DialogActivity.class); i.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK); i.putExtra(Constants.EXTRA_SCRIPT_PATH, fileName); startActivity(i); } else { Log .e(this, "Cannot find an interpreter for script " + fileName); } stopSelf(startId); return; } // Copies script to internal memory. fileName = InterpreterUtils.getInterpreterRoot(this).getAbsolutePath() + "/" + fileName; File script = new File(fileName); // TODO(raaar): Check size here! if (!script.exists()) { script = FileUtils.copyFromStream(fileName, getResources() .openRawResource(Script.ID)); } copyResourcesToLocal(); // Copy all resources if (Script.getFileExtension(this) .equals(HtmlInterpreter.HTML_EXTENSION)) { HtmlActivityTask htmlTask = ScriptLauncher.launchHtmlScript(script, this, intent, mInterpreterConfiguration); mFacadeManager = htmlTask.getRpcReceiverManager(); mLatch.countDown(); stopSelf(startId); } else { mProxy = new AndroidProxy(this, null, true); mProxy.startLocal(); mLatch.countDown(); ScriptLauncher.launchScript(script, mInterpreterConfiguration, mProxy, new Runnable() { @Override public void run() { mProxy.shutdown(); stopSelf(startId); } }); } } RpcReceiverManager getRpcReceiverManager() throws InterruptedException { mLatch.await(); if (mFacadeManager==null) { // Facade manage may not be available on startup. mFacadeManager = mProxy.getRpcReceiverManagerFactory() .getRpcReceiverManagers().get(0); } return mFacadeManager; } @Override protected Notification createNotification() { Notification notification = new Notification(R.drawable.script_logo_48, this.getString(R.string.loading), System.currentTimeMillis()); // This contentIntent is a noop. PendingIntent contentIntent = PendingIntent.getService(this, 0, new Intent(), 0); notification.setLatestEventInfo(this, this.getString(R.string.app_name), this.getString(R.string.loading), contentIntent); notification.flags = Notification.FLAG_ONGOING_EVENT; return notification; }

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Problems with Asynchronous UDP Sockets

- by ihatenetworkcoding

Hi, I'm struggling a bit with socket programming (something I'm not at all familiar with) and I can't find anything which helps from google or MSDN (awful). Apologies for the length of this. Basically I have an existing service which recieves and responds to requests over UDP. I can't change this at all. I also have a client within my webapp which dispatches and listens for responses to that service. The existing client I've been given is a singleton which creates a socket and an array of response slots, and then creates a background thread with an infinite looping method that makes "sock.Receive()" calls and pushes the data received into the slot array. All kinds of things about this seem wrong to me and the infinite thread breaks my unit testing so I'm trying to replace this service with one which makes it's it's send/receives asynchronously instead. Point 1: Is this the right approach? I want a non-blocking, scalable, thread-safe service. My first attempt is roughly like this, which sort of worked but the data I got back was always shorter than expected (i.e. the buffer did not have the number of bytes requested) and seemed to throw exceptions when processed. private Socket MyPreConfiguredSocket; public object Query() { //build a request this.MyPreConfiguredSocket.SendTo(MYREQUEST, packet.Length, SocketFlags.Multicast, this._target); IAsyncResult h = this._sock.BeginReceiveFrom(response, 0, BUFFER_SIZE, SocketFlags.None, ref this._target, new AsyncCallback(ARecieve), this._sock); if (!h.AsyncWaitHandle.WaitOne(TIMEOUT)) { throw new Exception("Timed out"); } //process response data (always shortened) } private void ARecieve (IAsyncResult result) { int bytesreceived = (result as Socket).EndReceiveFrom(result, ref this._target); } My second attempt was based on more google trawling and this recursive pattern I frequently saw, but this version always times out! It never gets to ARecieve. public object Query() { //build a request this.MyPreConfiguredSocket.SendTo(MYREQUEST, packet.Length, SocketFlags.Multicast, this._target); State s = new State(this.MyPreConfiguredSocket); this.MyPreConfiguredSocket.BeginReceiveFrom(s.Buffer, 0, BUFFER_SIZE, SocketFlags.None, ref this._target, new AsyncCallback(ARecieve), s); if (!s.Flag.WaitOne(10000)) { throw new Exception("Timed out"); } //always thrown //process response data } private void ARecieve (IAsyncResult result) { //never gets here! State s = (result as State); int bytesreceived = s.Sock.EndReceiveFrom(result, ref this._target); if (bytesreceived > 0) { s.Received += bytesreceived; this._sock.BeginReceiveFrom(s.Buffer, s.Received, BUFFER_SIZE, SocketFlags.None, ref this._target, new AsyncCallback(ARecieve), s); } else { s.Flag.Set(); } } private class State { public State(Socket sock) { this._sock = sock; this._buffer = new byte[BUFFER_SIZE]; this._buffer.Initialize(); } public Socket Sock; public byte[] Buffer; public ManualResetEvent Flag = new ManualResetEvent(false); public int Received = 0; } Point 2: So clearly I'm getting something quite wrong. Point 3: I'm not sure if I'm going about this right. How does the data coming from the remote service even get to the right listening thread? Do I need to create a socket per request? Out of my comfort zone here. Need help.

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C++ Compound Interest Exercise

- by Lameste

I'm a beginner trying to learn C++ using "C++ Primer Plus Sixth Edition". I'm on Chapter 5, going over loops. Anyways I was doing this programming exercise from the book, the problem is: Daphne invests $100 at 10% simple interest.That is, every year, the investment earns 10% of the original investment, or $10 each and every year: interest = 0.10 × original balance At the same time, Cleo invests $100 at 5% compound interest.That is, interest is 5% of the current balance, including previous additions of interest: interest = 0.05 × current balance Cleo earns 5% of $100 the first year, giving her $105.The next year she earns 5% of $105, or $5.25, and so on.Write a program that finds how many years it takes for the value of Cleo’s investment to exceed the value of Daphne’s investment and then displays the value of both investments at that time. Here is the code I have written for this exercise, I'm not getting good results though. #include <iostream> #include <array> double Daphne(int, double, double); double Chleo(double, double); int main() { using namespace std; int p = 100; //Principle double i1 = 0.1; // 10% interest rate double i2 = 0.05; // 5% interest rate double dInv = 0; //Daphnes investment double cInv = 0; // Chleos investment int t=1; //Starting at year 1 double s1 = 0; //Sum 1 for Daphne double s2 = 0; // Sum 2 for Chleo s1 = p + 10; //Initial interest (base case after year 1) for Daphne s2 = p + (i2*p); //Initial interest (base case after year 1) for Chleo /*cout << s1 << endl; cout << s2 << endl;*/ while (cInv < dInv) { dInv = Daphne(p, i1, s1); cInv = Chleo(i2, s2); t++; } cout << "The time taken for Chleos investment to exceed Daphnes was: " << t << endl; cout << "Daphnes investment at " << t << " years is: " << dInv << endl; cout << "Chleos invesment at " << t << " years is: " << cInv << endl; system("pause"); return 0; } double Daphne(int p, double i, double s1) { s1 = s1 + (p*i); return s1; } double Chleo(double i, double s2){ s2 = s2 + (s2*i); return s2; } Output from console: The time taken for Chleos investment to exceed Daphnes was: 1 Daphnes investment at 1 years is: 0 Chleos invesment at 1 years is: 0 Press any key to continue . . . Can anyone explain why I'm getting this current result? The while loop is supposed to continue executing statements until Chleo's investment exceeds Daphnes.

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Double Linked List header node keeps returning first value as 0

- by Craig

I will preface to say that this is my first question. I am currently getting my Masters degree in Information Security and I had to take C++ programming this semester. So this is homework related. I am not looking for you to answer my homework but I am running into a peculiar situation. I have created the program to work with a doubly linked list and everything works fine. However when I have the user create a list of values the first node keeps returning 0. I have tried finding some reading on this and I cannot locate any reference to it. My question is then is the header node(first node) always going to be zero? Or am I doing something wrong. case: 'C': cout<<"Please enter a list:"<<endl; while(n!=-999){ myList.insert(n); cin>> n;} break; I now enter: 12321, 1234,64564,346346. The results in 0, 12321, 1234, 64564,346346. Is this what should happen or am I doing something wrong? Also as this is my first post please feel free to criticize or teach me how to color code the keywords. Anyway this is a homework assignment so I am only looking for guidance and constructive criticism. Thank you all in advance So I cannot figure out the comment sections on this forum so I will edit the original post The first section is the constructor code: template <class Type> doublyLinkedList<Type>::doublyLinkedList() { first= NULL; last = NULL; count = 0; } Then there is my insert function : template <class Type> void doublyLinkedList<Type>::insert(const Type& insertItem) { nodeType<Type> *current; //pointer to traverse the list nodeType<Type> *trailCurrent; //pointer just before current nodeType<Type> *newNode; //pointer to create a node bool found; newNode = new nodeType<Type>; //create the node newNode->info = insertItem; //store the new item in the node newNode->next = NULL; newNode->back = NULL; if(first == NULL) //if the list is empty, newNode is //the only node { first = newNode; last = newNode; count++; } else { found = false; current = first; while (current != NULL && !found) //search the list if (current->info >= insertItem) found = true; else { trailCurrent = current; current = current->next; } if (current == first) //insert newNode before first { first->back = newNode; newNode->next = first; first = newNode; count++; } else { //insert newNode between trailCurrent and current if (current != NULL) { trailCurrent->next = newNode; newNode->back = trailCurrent; newNode->next = current; current->back = newNode; } else { trailCurrent->next = newNode; newNode->back = trailCurrent; last = newNode; } count++; }//end else }//end else }//end Then I have an initialization function too: template <class Type> void doublyLinkedList<Type>::initializeList() { destroy(); } Did I miss anything?

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Weird GWT issue causing IE threads to skyrocket.

- by WesleyJohnson

I'm not sure if this is an issue with GWT, JavaScript, Java, IE or just poor programming, but I'll try to explain. We're implementing web based chat program at work and some of our users have unreliable connections. So we're running into issues where they send out a new message and after x number of milliseconds have passed, the XHR request timesout and the client tries to resend the message again. The issue we ran into was sometimes the message would make it to the server and into the DB, but the XHR request wouldn't make it back to the client so the client was essentially retrying requests that had alread made it to the server. To mitigate this issue, we now send along a count/key with the message. The client says, hey I'm sending msg 50 and it's text is this. If the server already has that message, it just sends back "ok, I got it" and doens't insert into the DB again, eliminating dupes. So the client is free to keep retrying over and over until finally a call comes back from the server saying "Ok, I got it" and then it increments the key and moves on (or we keep them out of the chat if it fails enough). Anyway, so that's the background of what we're doing. The issue is, when we add this code on some versions of IE the threads start increasing gradually everytime it's accessed. On IE8 for Windows7 x64 it doesn't really seem to do it, but on IE8 for Windows Vista x86 it does. So I can't really pinpoint if it's a fluke or my code. Maybe someone had some ideas on a better way to do this. Here is some pseudo code: (the issue seems appear where I increment messageCount? Is this a scope thing, naming conflict, maybe the issue is entirely somewhere else and I'm way off base. public class SFChatClient implements EntryPoint { private List<String> messageQueue; private Integer messageCount = 0; public void onModuleLoad() { messageQueue = new ArrayList<String>(); // setup ui and what not // add a keyhandler to an input box that checks for <ENTER> and calls sendMEssage() } private void sendMessage() { // add message content to the UI for the chat messageQueue.add( //get message from user ); sendQueuedMessages(); } private void sendQueuedMessages() { if( messageQueue.size() > 0 ) { String outgoingMessage = messageQueue.get( 0 ); WebServiceClass.sendMessage( outgoingMessage, messageCount, new WebServiceHandler() { public void onSuccess() { // Delete item 0 from messageQueue messageCount = messageCount + 1; // <--- this seems to cause IE to leak threads. Taking out this code stops the issue??? sendQueuedMessages(); } public void onError() { // Do error handling sendQueuedMessages(); } } ); } } } public class WebServiceClass() { public void sendMessage( String message, Integer messageCount, handler ) { RequestBuilder builder = new RequestBuilder(// create request builder with proper params for the web service url, JSON content type, etc ) { public void onSuccess() { handler.onSuccess() } public void onError() { handler.onError() } } builder.setData( // JSON with message ); bulder.send(); } }

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Runtime error in C code (strange double conversion)

- by Miro Hassan

I have a strange runtime error in my C code. The Integers comparison here works fine. But in the Decimals comparison, I always get that the second number is larger than the first number, which is false. I am pretty new to C and programming in general, so this is a complex application to me. #include <stdio.h> #include <stdbool.h> #include <stdlib.h> int choose; long long neLimit = -1000000000; long long limit = 1000000000; bool big(a,b) { if ((a >= limit) || (b >= limit)) return true; else if ((a <= neLimit) || (b <= neLimit)) return true; return false; } void largerr(a,b) { if (a > b) printf("\nThe First Number is larger ..\n"); else if (a < b) printf("\nThe Second Number is larger ..\n"); else printf("\nThe Two Numbers are Equal .. \n"); } int main() { system("color e && title Numbers Comparison && echo off && cls"); start:{ printf("Choose a Type of Comparison :\n\t1. Integers\n\t2. Decimals \n\t\t I Choose Number : "); scanf("%i", &choose); switch(choose) { case 1: goto Integers; break; case 2: goto Decimals; break; default: system("echo Please Choose a Valid Option && pause>nul && cls"); goto start; } } Integers: { system("title Integers Comparison && cls"); long x , y; printf("\nFirst Number : \t"); scanf("%li", &x); printf("\nSecond Number : "); scanf("%li", &y); if (big(x,y)) { printf("\nOut of Limit .. Too Big Numbers ..\n"); system("pause>nul && cls") ; goto Integers; } largerr(x,y); printf("\nFirst Number : %li\nSecond Number : %li\n",x,y); goto exif; } Decimals: { system("title Decimals Comparison && cls"); double x , y; printf("\nFirst Number : \t"); scanf("%le", &x); printf("\nSecond Number : "); scanf("%le", &y); if (big(x,y)) { printf("\nOut of Limit .. Too Big Numbers ..\n"); system("pause>nul && cls") ; goto Decimals; } largerr(x,y); goto exif; } exif:{ system("pause>nul"); system("cls"); main(); } }

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Unable to get my master & details gridview to work.

- by Javier

I'm unable to get this to work. I'm very new at programming and would appreciate any help on this. <%@ Page Language="C#" %> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <script runat="server"> protected void Page_Load(object sender, EventArgs e) { } protected void DataGridSqlDataSource_Selecting(object sender, SqlDataSourceSelectingEventArgs e) { } </script> <html xmlns="http://www.w3.org/1999/xhtml"> <head runat="server"> <title>Untitled Page</title> </head> <body> <form id="form1" runat="server"> <div> <asp:SqlDataSource ID="DataGrid2SqlDataSource" runat="server" ConnectionString="<%$ ConnectionStrings:JobPostings1ConnectionString %>" SelectCommand="SELECT [Jobs_PK], [Position_Title], [Educ_Level], [Grade], [JP_Description], [Job_Status], [Position_ID] FROM [Jobs]" FilterExpression="Jobs_PK='@Jobs_PK'"> <filterparameters> <asp:ControlParameter Name="Jobs_PK" ControlId="GridView1" PropertyName="SelectedValue" /> </filterparameters> </asp:SqlDataSource> <asp:SqlDataSource ID="DataGridSqlDataSource" runat="server" ConnectionString="<%$ ConnectionStrings:JobPostings1ConnectionString %>" SelectCommand="SELECT [Position_Title], [Jobs_PK] FROM [Jobs]" onselecting="DataGridSqlDataSource_Selecting"> </asp:SqlDataSource> <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" DataKeyNames="Jobs_PK" DataSourceID="DataGridSqlDataSource" AllowPaging="True" AutoGenerateSelectButton="True" SelectedIndex="0" Width="100px"> <Columns> <asp:BoundField DataField="Position_Title" HeaderText="Position_Title" SortExpression="Position_Title" /> <asp:BoundField DataField="Jobs_PK" HeaderText="Jobs_PK" InsertVisible="False" ReadOnly="True" SortExpression="Jobs_PK" /> </Columns> </asp:GridView> <br /> <asp:DetailsView ID="DetailsView1" runat="server" AutoGenerateRows="False" DataKeyNames="Jobs_PK" DataSourceID="DataGrid2SqlDataSource" Height="50px" Width="125px"> <Fields> <asp:BoundField DataField="Jobs_PK" HeaderText="Jobs_PK" InsertVisible="False" ReadOnly="True" SortExpression="Jobs_PK" /> <asp:BoundField DataField="Position_Title" HeaderText="Position_Title" SortExpression="Position_Title" /> <asp:BoundField DataField="Educ_Level" HeaderText="Educ_Level" SortExpression="Educ_Level" /> <asp:BoundField DataField="Grade" HeaderText="Grade" SortExpression="Grade" /> <asp:BoundField DataField="JP_Description" HeaderText="JP_Description" SortExpression="JP_Description" /> <asp:BoundField DataField="Job_Status" HeaderText="Job_Status" SortExpression="Job_Status" /> <asp:BoundField DataField="Position_ID" HeaderText="Position_ID" SortExpression="Position_ID" /> </Fields> </asp:DetailsView> </div> </form> </body> error message: Cannot perform '=' operation on System.Int32 and System.String. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.Data.EvaluateException: Cannot perform '=' operation on System.Int32 and System.String.

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Function for counting characters/words not working

- by user1742729

<!DOCTYPE HTML> <html> <head> <title> Javascript - stuff </title> <script type="text/javascript">  </script> </head> <body> <div id="Text"> It is important to remember that XHTML is a markup language; it is not a programming language. The language only describes the placement and visual appearance of elements arranged on a page; it does not permit users to manipulate these elements to change their placement or appearance, or to perform any "processing" on the text or graphics to change their content in response to user needs. For many Web pages this lack of processing capability is not a great drawback; the pages are simply displays of static, unchanging, information for which no manipulation by the user is required. Still, there are cases where the ability to respond to user actions and the availability of processing methods can be a great asset. This is where JavaScript enters the picture. </div> <input type = "button" value = "Get Counts" class = "btnstyle" onclick = "GetCountsAll()"/> <br/> <span id= "Charactercount"> </span> Characters <br/> <span id= "Wordcount"> </span> Words <br/> <span id= "Sentancecount"> </span> Sentences <br/> <span id= "ClauseCount"> </span> Clauses <br/> </body> </html> I am a student and still learning JavaScript, so excuse any horrible mistakes. The script is meant to calculate the number of characters, words, sentences, and clauses in the passage. It's, plainly put, just not working. I have tried a multitude of things to get it to work for me and have gotten a plethora of different errors but no matter what I can NOT get this to work. Please help! (btw i know i misspelled sentence)

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NoSQL with MongoDB, NoRM and ASP.NET MVC

- by shiju

In this post, I will give an introduction to how to work on NoSQL and document database with MongoDB , NoRM and ASP.Net MVC 2. NoSQL and Document Database The NoSQL movement is getting big attention in this year and people are widely talking about document databases and NoSQL along with web application scalability. According to Wikipedia, "NoSQL is a movement promoting a loosely defined class of non-relational data stores that break with a long history of relational databases. These data stores may not require fixed table schemas, usually avoid join operations and typically scale horizontally. Academics and papers typically refer to these databases as structured storage". Document databases are schema free so that you can focus on the problem domain and don't have to worry about updating the schema when your domain is evolving. This enables truly a domain driven development. One key pain point of relational database is the synchronization of database schema with your domain entities when your domain is evolving.There are lots of NoSQL implementations are available and both CouchDB and MongoDB got my attention. While evaluating both CouchDB and MongoDB, I found that CouchDB can’t perform dynamic queries and later I picked MongoDB over CouchDB. There are many .Net drivers available for MongoDB document database. MongoDB MongoDB is an open source, scalable, high-performance, schema-free, document-oriented database written in the C++ programming language. It has been developed since October 2007 by 10gen. MongoDB stores your data as binary JSON (BSON) format . MongoDB has been getting a lot of attention and you can see the some of the list of production deployments from here - http://www.mongodb.org/display/DOCS/Production+Deployments NoRM – C# driver for MongoDB NoRM is a C# driver for MongoDB with LINQ support. NoRM project is available on Github at http://github.com/atheken/NoRM. Demo with ASP.NET MVC I will show a simple demo with MongoDB, NoRM and ASP.NET MVC. To work with MongoDB and NoRM, do the following steps Download the MongoDB databse For Windows 32 bit, download from http://downloads.mongodb.org/win32/mongodb-win32-i386-1.4.1.zip and for Windows 64 bit, download from http://downloads.mongodb.org/win32/mongodb-win32-x86_64-1.4.1.zip . The zip contains the mongod.exe for run the server and mongo.exe for the client Download the NorM driver for MongoDB at http://github.com/atheken/NoRM Create a directory call C:\data\db. This is the default location of MongoDB database. You can override the behavior. Run C:\Mongo\bin\mongod.exe. This will start the MongoDb server Now I am going to demonstrate how to program with MongoDb and NoRM in an ASP.NET MVC application.Let’s write a domain class public class Category { [MongoIdentifier]public ObjectId Id { get; set; } [Required(ErrorMessage = "Name Required")][StringLength(25, ErrorMessage = "Must be less than 25 characters")]public string Name { get; set;}public string Description { get; set; }} ObjectId is a NoRM type that represents a MongoDB ObjectId. NoRM will automatically update the Id becasue it is decorated by the MongoIdentifier attribute. The next step is to create a mongosession class. This will do the all interactions to the MongoDB. internal class MongoSession<TEntity> : IDisposable{ private readonly MongoQueryProvider provider; public MongoSession() { this.provider = new MongoQueryProvider("Expense"); } public IQueryable<TEntity> Queryable { get { return new MongoQuery<TEntity>(this.provider); } } public MongoQueryProvider Provider { get { return this.provider; } } public void Add<T>(T item) where T : class, new() { this.provider.DB.GetCollection<T>().Insert(item); } public void Dispose() { this.provider.Server.Dispose(); } public void Delete<T>(T item) where T : class, new() { this.provider.DB.GetCollection<T>().Delete(item); } public void Drop<T>() { this.provider.DB.DropCollection(typeof(T).Name); } public void Save<T>(T item) where T : class,new() { this.provider.DB.GetCollection<T>().Save(item); } } The MongoSession constrcutor will create an instance of MongoQueryProvider that supports the LINQ expression and also create a database with name "Expense". If database is exists, it will use existing database, otherwise it will create a new databse with name "Expense". The Save method can be used for both Insert and Update operations. If the object is new one, it will create a new record and otherwise it will update the document with given ObjectId. Let’s create ASP.NET MVC controller actions for CRUD operations for the domain class Category public class CategoryController : Controller{ //Index - Get the category listpublic ActionResult Index(){ using (var session = new MongoSession<Category>()) { var categories = session.Queryable.AsEnumerable<Category>(); return View(categories); }} //edit a single category[HttpGet]public ActionResult Edit(ObjectId id) { using (var session = new MongoSession<Category>()) { var category = session.Queryable .Where(c => c.Id == id) .FirstOrDefault(); return View("Save",category); } }// GET: /Category/Create[HttpGet]public ActionResult Create(){ var category = new Category(); return View("Save", category);}//insert or update a category[HttpPost]public ActionResult Save(Category category){ if (!ModelState.IsValid) { return View("Save", category); } using (var session = new MongoSession<Category>()) { session.Save(category); return RedirectToAction("Index"); } }//Delete category[HttpPost]public ActionResult Delete(ObjectId Id){ using (var session = new MongoSession<Category>()) { var category = session.Queryable .Where(c => c.Id == Id) .FirstOrDefault(); session.Delete(category); var categories = session.Queryable.AsEnumerable<Category>(); return PartialView("CategoryList", categories); } } } You can easily work on MongoDB with NoRM and can use with ASP.NET MVC applications. I have created a repository on CodePlex at http://mongomvc.codeplex.com and you can download the source code of the ASP.NET MVC application from here

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Parallelism in .NET – Part 3, Imperative Data Parallelism: Early Termination

- by Reed

Although simple data parallelism allows us to easily parallelize many of our iteration statements, there are cases that it does not handle well. In my previous discussion, I focused on data parallelism with no shared state, and where every element is being processed exactly the same. Unfortunately, there are many common cases where this does not happen. If we are dealing with a loop that requires early termination, extra care is required when parallelizing. Often, while processing in a loop, once a certain condition is met, it is no longer necessary to continue processing. This may be a matter of finding a specific element within the collection, or reaching some error case. The important distinction here is that, it is often impossible to know until runtime, what set of elements needs to be processed. In my initial discussion of data parallelism, I mentioned that this technique is a candidate when you can decompose the problem based on the data involved, and you wish to apply a single operation concurrently on all of the elements of a collection. This covers many of the potential cases, but sometimes, after processing some of the elements, we need to stop processing. As an example, lets go back to our previous Parallel.ForEach example with contacting a customer. However, this time, we’ll change the requirements slightly. In this case, we’ll add an extra condition – if the store is unable to email the customer, we will exit gracefully. The thinking here, of course, is that if the store is currently unable to email, the next time this operation runs, it will handle the same situation, so we can just skip our processing entirely. The original, serial case, with this extra condition, might look something like the following: foreach(var customer in customers) { // Run some process that takes some time... DateTime lastContact = theStore.GetLastContact(customer); TimeSpan timeSinceContact = DateTime.Now - lastContact; // If it's been more than two weeks, send an email, and update... if (timeSinceContact.Days > 14) { // Exit gracefully if we fail to email, since this // entire process can be repeated later without issue. if (theStore.EmailCustomer(customer) == false) break; customer.LastEmailContact = DateTime.Now; } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Here, we’re processing our loop, but at any point, if we fail to send our email successfully, we just abandon this process, and assume that it will get handled correctly the next time our routine is run. If we try to parallelize this using Parallel.ForEach, as we did previously, we’ll run into an error almost immediately: the break statement we’re using is only valid when enclosed within an iteration statement, such as foreach. When we switch to Parallel.ForEach, we’re no longer within an iteration statement – we’re a delegate running in a method. This needs to be handled slightly differently when parallelized. Instead of using the break statement, we need to utilize a new class in the Task Parallel Library: ParallelLoopState. The ParallelLoopState class is intended to allow concurrently running loop bodies a way to interact with each other, and provides us with a way to break out of a loop. In order to use this, we will use a different overload of Parallel.ForEach which takes an IEnumerable<T> and an Action<T, ParallelLoopState> instead of an Action<T>. Using this, we can parallelize the above operation by doing: Parallel.ForEach(customers, (customer, parallelLoopState) => { // Run some process that takes some time... DateTime lastContact = theStore.GetLastContact(customer); TimeSpan timeSinceContact = DateTime.Now - lastContact; // If it's been more than two weeks, send an email, and update... if (timeSinceContact.Days > 14) { // Exit gracefully if we fail to email, since this // entire process can be repeated later without issue. if (theStore.EmailCustomer(customer) == false) parallelLoopState.Break(); else customer.LastEmailContact = DateTime.Now; } }); There are a couple of important points here. First, we didn’t actually instantiate the ParallelLoopState instance. It was provided directly to us via the Parallel class. All we needed to do was change our lambda expression to reflect that we want to use the loop state, and the Parallel class creates an instance for our use. We also needed to change our logic slightly when we call Break(). Since Break() doesn’t stop the program flow within our block, we needed to add an else case to only set the property in customer when we succeeded. This same technique can be used to break out of a Parallel.For loop. That being said, there is a huge difference between using ParallelLoopState to cause early termination and to use break in a standard iteration statement. When dealing with a loop serially, break will immediately terminate the processing within the closest enclosing loop statement. Calling ParallelLoopState.Break(), however, has a very different behavior. The issue is that, now, we’re no longer processing one element at a time. If we break in one of our threads, there are other threads that will likely still be executing. This leads to an important observation about termination of parallel code: Early termination in parallel routines is not immediate. Code will continue to run after you request a termination. This may seem problematic at first, but it is something you just need to keep in mind while designing your routine. ParallelLoopState.Break() should be thought of as a request. We are telling the runtime that no elements that were in the collection past the element we’re currently processing need to be processed, and leaving it up to the runtime to decide how to handle this as gracefully as possible. Although this may seem problematic at first, it is a good thing. If the runtime tried to immediately stop processing, many of our elements would be partially processed. It would be like putting a return statement in a random location throughout our loop body – which could have horrific consequences to our code’s maintainability. In order to understand and effectively write parallel routines, we, as developers, need a subtle, but profound shift in our thinking. We can no longer think in terms of sequential processes, but rather need to think in terms of requests to the system that may be handled differently than we’d first expect. This is more natural to developers who have dealt with asynchronous models previously, but is an important distinction when moving to concurrent programming models. As an example, I’ll discuss the Break() method. ParallelLoopState.Break() functions in a way that may be unexpected at first. When you call Break() from a loop body, the runtime will continue to process all elements of the collection that were found prior to the element that was being processed when the Break() method was called. This is done to keep the behavior of the Break() method as close to the behavior of the break statement as possible. We can see the behavior in this simple code: var collection = Enumerable.Range(0, 20); var pResult = Parallel.ForEach(collection, (element, state) => { if (element > 10) { Console.WriteLine("Breaking on {0}", element); state.Break(); } Console.WriteLine(element); }); If we run this, we get a result that may seem unexpected at first: 0 2 1 5 6 3 4 10 Breaking on 11 11 Breaking on 12 12 9 Breaking on 13 13 7 8 Breaking on 15 15 What is occurring here is that we loop until we find the first element where the element is greater than 10. In this case, this was found, the first time, when one of our threads reached element 11. It requested that the loop stop by calling Break() at this point. However, the loop continued processing until all of the elements less than 11 were completed, then terminated. This means that it will guarantee that elements 9, 7, and 8 are completed before it stops processing. You can see our other threads that were running each tried to break as well, but since Break() was called on the element with a value of 11, it decides which elements (0-10) must be processed. If this behavior is not desirable, there is another option. Instead of calling ParallelLoopState.Break(), you can call ParallelLoopState.Stop(). The Stop() method requests that the runtime terminate as soon as possible , without guaranteeing that any other elements are processed. Stop() will not stop the processing within an element, so elements already being processed will continue to be processed. It will prevent new elements, even ones found earlier in the collection, from being processed. Also, when Stop() is called, the ParallelLoopState’s IsStopped property will return true. This lets longer running processes poll for this value, and return after performing any necessary cleanup. The basic rule of thumb for choosing between Break() and Stop() is the following. Use ParallelLoopState.Stop() when possible, since it terminates more quickly. This is particularly useful in situations where you are searching for an element or a condition in the collection. Once you’ve found it, you do not need to do any other processing, so Stop() is more appropriate. Use ParallelLoopState.Break() if you need to more closely match the behavior of the C# break statement. Both methods behave differently than our C# break statement. Unfortunately, when parallelizing a routine, more thought and care needs to be put into every aspect of your routine than you may otherwise expect. This is due to my second observation: Parallelizing a routine will almost always change its behavior. This sounds crazy at first, but it’s a concept that’s so simple its easy to forget. We’re purposely telling the system to process more than one thing at the same time, which means that the sequence in which things get processed is no longer deterministic. It is easy to change the behavior of your routine in very subtle ways by introducing parallelism. Often, the changes are not avoidable, even if they don’t have any adverse side effects. This leads to my final observation for this post: Parallelization is something that should be handled with care and forethought, added by design, and not just introduced casually.

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Mauritius Software Craftsmanship Community

There we go! I finally managed to push myself forward and pick up an old, actually too old, idea since I ever arrived here in Mauritius more than six years ago. I'm talking about a community for all kind of ICT connected people. In the past (back in Germany), I used to be involved in various community activities. For example, I was part of the Microsoft Community Leader/Influencer Program (CLIP) in Germany due to an FAQ on Visual FoxPro, actually Active FoxPro Pages (AFP) to be more precise. Then in 2003/2004 I addressed the responsible person of the dFPUG user group in Speyer in order to assist him in organising monthly user group meetings. Well, he handed over management completely, and attended our meetings regularly. Why did it take you so long? Well, I don't want to bother you with the details but short version is that I was too busy on either job (building up new companies) or private life (got married and we have two lovely children, eh 'monsters') or even both. But now is the time where I was starting to look for new fields given the fact that I gained some spare time. My businesses are up and running, the kids are in school, and I am finally in a position where I can commit myself again to community activities. And I love to do that! Why a new user group? Good question... And 'easy' to answer. Since back in 2007 I did my usual research, eh Google searches, to see whether there existing user groups in Mauritius and in which field of interest. And yes, there are! If I recall this correctly, then there are communities for PHP, Drupal, Python (just recently), Oracle, and Linux (which used to be even two). But... either they do not exist anymore, they are dormant, or there is only a low heart-beat, frankly speaking. And yes, I went to meetings of the Linux User Group Meta (Mauritius) back in 2010/2011 and just recently. I really like the setup and the way the LUGM is organised. It's just that I have a slightly different point of view on how a user group or community should organise itself and how to approach future members. Don't get me wrong, I'm not criticizing others doing a very good job, I'm only saying that I'd like to do it differently. The last meeting of the LUGM was awesome; read my feedback about it. Ok, so what's up with 'Mauritius Software Craftsmanship Community' or short: MSCC? As I've already written in my article on 'Communities - The importance of exchange and discussion' I think it is essential in a world of IT to stay 'connected' with a good number of other people in the same field. There is so much dynamic and every day's news that it is almost impossible to keep on track with all of them. The MSCC is going to provide a common platform to exchange experience and share knowledge between each other. You might be a newbie and want to know what to expect working as a software developer, or as a database administrator, or maybe as an IT systems administrator, or you're an experienced geek that loves to share your ideas or solutions that you implemented to solve a specific problem, or you're the business (or HR) guy that is looking for 'fresh' blood to enforce your existing team. Or... you're just interested and you'd like to communicate with like-minded people. Meetup of 26.06.2013 @ L'arabica: Of course there are laptops around. Free WiFi, power outlet, coffee, code and Linux in one go. The MSCC is technology-agnostic and spans an umbrella over any kind of technology. Simply because you can't ignore other technologies anymore in a connected IT world as we have. A front-end developer for iOS applications should have the chance to connect with a Python back-end coder and eventually with a DBA for MySQL or PostgreSQL and exchange their experience. Furthermore, I'm a huge fan of cross-platform development, and it is very pleasant to have pure Web developers - with all that HTML5, CSS3, JavaScript and JS libraries stuff - and passionate C# or Java coders at the same table. This diversity of knowledge can assist and boost your personal situation. And last but not least, there are projects and open positions 'flying' around... People might like to hear others opinion about an employer or get new impulses on how to tackle down an issue at their workspace, etc. This is about community. And that's how I see the MSCC in general - free of any limitations be it by programming language or technology. Having the chance to exchange experience and to discuss certain aspects of technology saves you time and money, and it's a pleasure to enjoy. Compared to dusty books and remote online resources. It's human! Organising meetups (meetings, get-together, gatherings - you name it!) As of writing this article, the MSCC is currently meeting every Wednesday for the weekly 'Code & Coffee' session at various locations (suggestions are welcome!) in Mauritius. This might change in the future eventually but especially at the beginning I think it is very important to create awareness in the Mauritian IT world. Yes, we are here! Come and join us! ;-) The MSCC's main online presence is located at Meetup.com because it allows me to handle the organisation of events and meeting appointments very easily, and any member can have a look who else is involved so that an exchange of contacts is given at any time. In combination with the other entities (G+ Communities, FB Pages or in Groups) I advertise and manage all future activities here: Mauritius Software Craftsmanship Community This is a community for those who care and are proud of what they do. For those developers, regardless how experienced they are, who want to improve and master their craft. This is a community for those who believe that being average is just not good enough. I know, there are not many 'craftsmen' yet but it's a start... Let's see how it looks like by the end of the year. There are free smartphone apps for Android and iOS from Meetup.com that allow you to keep track of meetings and to stay informed on latest updates. And last but not least, there is a Trello workspace to collect and share ideas and provide downloads of slides, etc. Trello is also available as free smartphone app. Sharing is caring! As mentioned, the #MSCC is present in various social media networks in order to cover as many people as possible here in Mauritius. Following is an overview of the current networks: Twitter - Latest updates and quickies Google+ - Community channel Facebook - Community Page LinkedIn - Community Group Trello - Collaboration workspace to share and develop ideas Hopefully, this covers the majority of computer-related people in Mauritius. Please spread the word about the #MSCC between your colleagues, your friends and other interested 'geeks'. Your future looks bright Running and participating in a user group or any kind of community usually provides quite a number of advantages for anyone. On the one side it is very joyful for me to organise appointments and get in touch with people that might be interested to present a little demo of their projects or their recent problems they had to tackle down, and on the other side there are lots of companies that have various support programs or sponsorships especially tailored for user groups. At the moment, I already have a couple of gimmicks that I would like to hand out in small contests or raffles during one of the upcoming meetings, and as said, companies provide all kind of goodies, books free of charge, or sometimes even licenses for communities. Meeting other software developers or IT guys also opens up your point of view on the local market and there might be interesting projects or job offers available, too. A community like the Mauritius Software Craftsmanship Community is great for freelancers, self-employed, students and of course employees. Meetings will be organised on a regular basis, and I'm open to all kind of suggestions from you. Please leave a comment here in blog or join the conversations in the above mentioned social networks. Let's get this community up and running, my fellow Mauritians! Recent updates The MSCC is now officially participating in the O'Reilly UK User Group programm and we are allowed to request review or recension copies of recent titles. Additionally, we have a discount code for any books or ebooks that you might like to order on shop.oreilly.com. More applications for user group sponsorship programms are pending and I'm looking forward to a couple of announcement very soon. And... we need some kind of 'corporate identity' - Over at the MSCC website there is a call for action (or better said a contest with prizes) to create a unique design for the MSCC. This would include a decent colour palette, a logo, graphical banners for Meetup, Google+, Facebook, LinkedIn, etc. and of course badges for our craftsmen to add to their personal blogs and websites. Please spread the word and contribute. Thanks!

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Parallelism in .NET – Part 7, Some Differences between PLINQ and LINQ to Objects

- by Reed

In my previous post on Declarative Data Parallelism, I mentioned that PLINQ extends LINQ to Objects to support parallel operations. Although nearly all of the same operations are supported, there are some differences between PLINQ and LINQ to Objects. By introducing Parallelism to our declarative model, we add some extra complexity. This, in turn, adds some extra requirements that must be addressed. In order to illustrate the main differences, and why they exist, let’s begin by discussing some differences in how the two technologies operate, and look at the underlying types involved in LINQ to Objects and PLINQ . LINQ to Objects is mainly built upon a single class: Enumerable. The Enumerable class is a static class that defines a large set of extension methods, nearly all of which work upon an IEnumerable<T>. Many of these methods return a new IEnumerable<T>, allowing the methods to be chained together into a fluent style interface. This is what allows us to write statements that chain together, and lead to the nice declarative programming model of LINQ: double min = collection .Where(item => item.SomeProperty > 6 && item.SomeProperty < 24) .Min(item => item.PerformComputation()); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Other LINQ variants work in a similar fashion. For example, most data-oriented LINQ providers are built upon an implementation of IQueryable<T>, which allows the database provider to turn a LINQ statement into an underlying SQL query, to be performed directly on the remote database. PLINQ is similar, but instead of being built upon the Enumerable class, most of PLINQ is built upon a new static class: ParallelEnumerable. When using PLINQ, you typically begin with any collection which implements IEnumerable<T>, and convert it to a new type using an extension method defined on ParallelEnumerable: AsParallel(). This method takes any IEnumerable<T>, and converts it into a ParallelQuery<T>, the core class for PLINQ. There is a similar ParallelQuery class for working with non-generic IEnumerable implementations. This brings us to our first subtle, but important difference between PLINQ and LINQ – PLINQ always works upon specific types, which must be explicitly created. Typically, the type you’ll use with PLINQ is ParallelQuery<T>, but it can sometimes be a ParallelQuery or an OrderedParallelQuery<T>. Instead of dealing with an interface, implemented by an unknown class, we’re dealing with a specific class type. This works seamlessly from a usage standpoint – ParallelQuery<T> implements IEnumerable<T>, so you can always “switch back” to an IEnumerable<T>. The difference only arises at the beginning of our parallelization. When we’re using LINQ, and we want to process a normal collection via PLINQ, we need to explicitly convert the collection into a ParallelQuery<T> by calling AsParallel(). There is an important consideration here – AsParallel() does not need to be called on your specific collection, but rather any IEnumerable<T>. This allows you to place it anywhere in the chain of methods involved in a LINQ statement, not just at the beginning. This can be useful if you have an operation which will not parallelize well or is not thread safe. For example, the following is perfectly valid, and similar to our previous examples: double min = collection .AsParallel() .Select(item => item.SomeOperation()) .Where(item => item.SomeProperty > 6 && item.SomeProperty < 24) .Min(item => item.PerformComputation()); However, if SomeOperation() is not thread safe, we could just as easily do: double min = collection .Select(item => item.SomeOperation()) .AsParallel() .Where(item => item.SomeProperty > 6 && item.SomeProperty < 24) .Min(item => item.PerformComputation()); In this case, we’re using standard LINQ to Objects for the Select(…) method, then converting the results of that map routine to a ParallelQuery<T>, and processing our filter (the Where method) and our aggregation (the Min method) in parallel. PLINQ also provides us with a way to convert a ParallelQuery<T> back into a standard IEnumerable<T>, forcing sequential processing via standard LINQ to Objects. If SomeOperation() was thread-safe, but PerformComputation() was not thread-safe, we would need to handle this by using the AsEnumerable() method: double min = collection .AsParallel() .Select(item => item.SomeOperation()) .Where(item => item.SomeProperty > 6 && item.SomeProperty < 24) .AsEnumerable() .Min(item => item.PerformComputation()); Here, we’re converting our collection into a ParallelQuery<T>, doing our map operation (the Select(…) method) and our filtering in parallel, then converting the collection back into a standard IEnumerable<T>, which causes our aggregation via Min() to be performed sequentially. This could also be written as two statements, as well, which would allow us to use the language integrated syntax for the first portion: var tempCollection = from item in collection.AsParallel() let e = item.SomeOperation() where (e.SomeProperty > 6 && e.SomeProperty < 24) select e; double min = tempCollection.AsEnumerable().Min(item => item.PerformComputation()); This allows us to use the standard LINQ style language integrated query syntax, but control whether it’s performed in parallel or serial by adding AsParallel() and AsEnumerable() appropriately. The second important difference between PLINQ and LINQ deals with order preservation. PLINQ, by default, does not preserve the order of of source collection. This is by design. In order to process a collection in parallel, the system needs to naturally deal with multiple elements at the same time. Maintaining the original ordering of the sequence adds overhead, which is, in many cases, unnecessary. Therefore, by default, the system is allowed to completely change the order of your sequence during processing. If you are doing a standard query operation, this is usually not an issue. However, there are times when keeping a specific ordering in place is important. If this is required, you can explicitly request the ordering be preserved throughout all operations done on a ParallelQuery<T> by using the AsOrdered() extension method. This will cause our sequence ordering to be preserved. For example, suppose we wanted to take a collection, perform an expensive operation which converts it to a new type, and display the first 100 elements. In LINQ to Objects, our code might look something like: // Using IEnumerable<SourceClass> collection IEnumerable<ResultClass> results = collection .Select(e => e.CreateResult()) .Take(100); If we just converted this to a parallel query naively, like so: IEnumerable<ResultClass> results = collection .AsParallel() .Select(e => e.CreateResult()) .Take(100); We could very easily get a very different, and non-reproducable, set of results, since the ordering of elements in the input collection is not preserved. To get the same results as our original query, we need to use: IEnumerable<ResultClass> results = collection .AsParallel() .AsOrdered() .Select(e => e.CreateResult()) .Take(100); This requests that PLINQ process our sequence in a way that verifies that our resulting collection is ordered as if it were processed serially. This will cause our query to run slower, since there is overhead involved in maintaining the ordering. However, in this case, it is required, since the ordering is required for correctness. PLINQ is incredibly useful. It allows us to easily take nearly any LINQ to Objects query and run it in parallel, using the same methods and syntax we’ve used previously. There are some important differences in operation that must be considered, however – it is not a free pass to parallelize everything. When using PLINQ in order to parallelize your routines declaratively, the same guideline I mentioned before still applies: Parallelization is something that should be handled with care and forethought, added by design, and not just introduced casually.

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Visual Studio 2013 Static Code Analysis in depth: What? When and How?

- by Hosam Kamel

In this post I'll illustrate in details the following points What is static code analysis? When to use? Supported platforms Supported Visual Studio versions How to use Run Code Analysis Manually Run Code Analysis Automatically Run Code Analysis while check-in source code to TFS version control (TFSVC) Run Code Analysis as part of Team Build Understand the Code Analysis results & learn how to fix them Create your custom rule set Q & A References What is static Rule analysis? Static Code Analysis feature of Visual Studio performs static code analysis on code to help developers identify potential design, globalization, interoperability, performance, security, and a lot of other categories of potential problems according to Microsoft's rules that mainly targets best practices in writing code, and there is a large set of those rules included with Visual Studio grouped into different categorized targeting specific coding issues like security, design, Interoperability, globalizations and others. Static here means analyzing the source code without executing it and this type of analysis can be performed through automated tools (like Visual Studio 2013 Code Analysis Tool) or manually through Code Review which already supported in Visual Studio 2012 and 2013 (check Using Code Review to Improve Quality video on Channel9) There is also Dynamic analysis which performed on executing programs using software testing techniques such as Code Coverage for example. When to use? Running Code analysis tool at regular intervals during your development process can enhance the quality of your software, examines your code for a set of common defects and violations is always a good programming practice. Adding that Code analysis can also find defects in your code that are difficult to discover through testing allowing you to achieve first level quality gate for you application during development phase before you release it to the testing team. Supported platforms .NET Framework, native (C and C++) Database applications. Support Visual Studio versions All version of Visual Studio starting Visual Studio 2013 (except Visual Studio Test Professional) check Feature comparisons Create and modify a custom rule set required Visual Studio Premium or Ultimate. How to use? Code Analysis can be run manually at any time from within the Visual Studio IDE, or even setup to automatically run as part of a Team Build or check-in policy for Team Foundation Server. Run Code Analysis Manually To run code analysis manually on a project, on the Analyze menu, click Run Code Analysis on your project or simply right click on the project name on the Solution Explorer choose Run Code Analysis from the context menu Run Code Analysis Automatically To run code analysis each time that you build a project, you select Enable Code Analysis on Build on the project's Property Page Run Code Analysis while check-in source code to TFS version control (TFSVC) Team Foundation Version Control (TFVC) provides a way for organizations to enforce practices that lead to better code and more efficient group development through Check-in policies which are rules that are set at the team project level and enforced on developer computers before code is allowed to be checked in. (This is available only if you're using Team Foundation Server) Require permissions on Team Foundation Server: you must have the Edit project-level information permission set to Allow typically your account must be part of Project Administrators, Project Collection Administrators, for more information about Team Foundation permissions check http://msdn.microsoft.com/en-us/library/ms252587(v=vs.120).aspx In Team Explorer, right-click the team project name, point to Team Project Settings, and then click Source Control. In the Source Control dialog box, select the Check-in Policy tab. Click Add to create a new check-in policy. Double-click the existing Code Analysis item in the Policy Type list to change the policy. Check or Uncheck the policy option based on the configurations you need to perform as illustrated below: Enforce check-in to only contain files that are part of current solution: code analysis can run only on files specified in solution and project configuration files. This policy guarantees that all code that is part of a solution is analyzed. Enforce C/C++ Code Analysis (/analyze): Requires that all C or C++ projects be built with the /analyze compiler option to run code analysis before they can be checked in. Enforce Code Analysis for Managed Code: Requires that all managed projects run code analysis and build before they can be checked in. Check Code analysis rule set reference on MSDN What is Rule Set? Rule Set is a group of code analysis rules like the example below where Microsoft.Design is the rule set name where "Do not declare static members on generic types" is the code analysis rule Once you configured the Analysis rule the policy will be enabled for all the team member in this project whenever a team member check-in any source code to the TFSVC the policy section will highlight the Code Analysis policy as below TFS is a very extensible platform so you can simply implement your own custom Code Analysis Check-in policy, check this link for more details http://msdn.microsoft.com/en-us/library/dd492668.aspx but you have to be aware also about compatibility between different TFS versions check http://msdn.microsoft.com/en-us/library/bb907157.aspx Run Code Analysis as part of Team Build With Team Foundation Build (TFBuild), you can create and manage build processes that automatically compile and test your applications, and perform other important functions. Code Analysis can be enabled in the Build Definition file by selecting the correct value for the build process parameter "Perform Code Analysis" Once configure, Kick-off your build definition to queue a new build, Code Analysis will run as part of build workflow and you will be able to see code analysis warning as part of build report Understand the Code Analysis results & learn how to fix them Now after you went through Code Analysis configurations and the different ways of running it, we will go through the Code Analysis result how to understand them and how to resolve them. Code Analysis window in Visual Studio will show all the analysis results based on the rule sets you configured in the project file properties, let's dig deep into what each result item contains: 1 Check ID The unique identifier for the rule. CheckId and Category are used for in-source suppression of a warning. 2 Title The title of warning message 3 Description A description of the problem or suggested fix 4 File Name File name and the line of code number which violate the code analysis rule set 5 Category The code analysis category for this error 6 Warning /Error Depend on how you configure it in the rule set the default is Warning level 7 Action Copy: copy the warning information to the clipboard Create Work Item: If you're connected to Team Foundation Server you can create a work item most probably you may create a Task or Bug and assign it for a developer to fix certain code analysis warning Suppress Message: There are times when you might decide not to fix a code analysis warning. You might decide that resolving the warning requires too much recoding in relation to the probability that the issue will arise in any real-world implementation of your code. Or you might believe that the analysis that is used in the warning is inappropriate for the particular context. You can suppress individual warnings so that they no longer appear in the Code Analysis window. Two options available: In Source inserts a SuppressMessage attribute in the source file above the method that generated the warning. This makes the suppression more discoverable. In Suppression File adds a SuppressMessage attribute to the GlobalSuppressions.cs file of the project. This can make the management of suppressions easier. Note that the SuppressMessage attribute added to GlobalSuppression.cs also targets the method that generated the warning. It does not suppress the warning globally. Visual Studio makes it very easy to fix Code analysis warning, all you have to do is clicking on the Check Id hyperlink if you are not aware how to fix the warring and you'll be directed to MSDN online or local copy based on the configuration you did while installing Visual Studio and you will find all the information about the warring including how to fix it. Create a Custom Code Analysis Rule Set The Microsoft standard rule sets provide groups of rules that are organized by function and depth. For example, the Microsoft Basic Design Guidelines Rules and the Microsoft Extended Design Guidelines Rules contain rules that focus on usability and maintainability issues, with added emphasis on naming rules in the Extended rule set, you can create and modify a custom rule set to meet specific project needs associated with code analysis. To create a custom rule set, you open one or more standard rule sets in the rule set editor. Create and modify a custom rule set required Visual Studio Premium or Ultimate. You can check How to: Create a Custom Rule Set on MSDN for more details http://msdn.microsoft.com/en-us/library/dd264974.aspx Q & A Visual Studio static code analysis vs. FxCop vs. StyleCpp http://www.excella.com/blog/stylecop-vs-fxcop-difference-between-code-analysis-tools/ Code Analysis for SharePoint Apps and SPDisposeCheck? This post lists some of the rule set you can run specifically for SharePoint applications and how to integrate SPDisposeCheck as well. Code Analysis for SQL Server Database Projects? This post illustrate how to run static code analysis on T-SQL through SSDT ReSharper 8 vs. Visual Studio 2013? This document lists some of the features that are provided by ReSharper 8 but are missing or not as fully implemented in Visual Studio 2013. References A Few Billion Lines of Code Later: Using Static Analysis to Find Bugs in the Real World http://cacm.acm.org/magazines/2010/2/69354-a-few-billion-lines-of-code-later/fulltext What is New in Code Analysis for Visual Studio 2013 http://blogs.msdn.com/b/visualstudioalm/archive/2013/07/03/what-is-new-in-code-analysis-for-visual-studio-2013.aspx Analyze the code quality of Windows Store apps using Visual Studio static code analysis http://msdn.microsoft.com/en-us/library/windows/apps/hh441471.aspx [Hands-on-lab] Using Code Analysis with Visual Studio 2012 to Improve Code Quality http://download.microsoft.com/download/A/9/2/A9253B14-5F23-4BC8-9C7E-F5199DB5F831/Using%20Code%20Analysis%20with%20Visual%20Studio%202012%20to%20Improve%20Code%20Quality.docx Originally posted at "Hosam Kamel| Developer & Platform Evangelist" http://blogs.msdn.com/hkamel

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500 Metro Style WP7 Icons

- by Bil Simser

I was inspired by The Noun Project, a project that offers up “Metro-style” icons in SVG format. The project is licensed under a public domain license and while it’s a great project, all of the content is in SVG format. Jon Galloway has a great post (from 2007) talking about the differences between SVG and XAML so I highly recommend that for some background. I thought it would be helpful to the WPF/Windows Phone 7/Silverlight community to provide the content in alternative formats for use in your applications. The Goods I’ve put together a package of the 500 icons (502 actually) in PNG, XAML and the original SVG format along with a couple of sample projects so you can see them in action. There’s a WPF desktop app: And a Windows Phone 7 app: Building It To get all the content first I wrote up a quick program to suck the original SVG files. Luckily they’re all in a common path just named 1.SVG, 2.SVG, and so on. Easy sleazy to grab the contents. Once I had 500 SVG files I used the latest copy of XamlTune, an open source CodePlex project that has a command line conversion tool to convert the directory of SVG files into XAML (the tool also created a PNG file of each SVG so that’s just icing on the cake). Conversions The conversion from SVG to XAML isn’t 100%. While you can just drop the content into a WPF app, it doesn’t work that way for WP7. There are just some small adjustments I made to each format so you’ll have to do the same. Follow the information below or refer to the sample applications. As a sample, here’s an icon we want to use: Here’s the original SVG file: <svg version="1.0" id="Layer_1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px" y="0px" width="100px" height="94.616px" viewBox="0 0 100 94.616" enable-background="new 0 0 100 94.616" xml:space="preserve"> <path d="M25.076,15.639c4.324,0.009,7.824-3.488,7.82-7.82C32.9,3.512,29.4,0.012,25.076,0c-4.313,0.012-7.814,3.512-7.821,7.819 C17.262,12.15,20.763,15.648,25.076,15.639L25.076,15.639z"/> <path d="M4.593,43.388h6.861l4.137-15.135h1.716L13.22,43.388h24.318l-4.389-15.135h1.817l2.32,7.415 c1.08,3.131,3.852,3.851,6.003,1.162l8.375-10.142c2.651-3.42-2.104-7.021-4.844-4.035l-4.993,5.952 c0.007,0.095-0.96-3.278-0.96-3.278c-1.135-3.978-4.918-7.903-10.595-7.922H19.576c-5.071,0.019-9.043,4.434-9.888,7.214 L4.593,43.388L4.593,43.388z"/> <polygon points="56.206,22.753 56.206,7.163 49.192,7.163 49.192,22.753 56.206,22.753 "/> <path d="M79.87,15.738c4.332-0.014,7.831-3.516,7.82-7.82c0.011-4.332-3.488-7.833-7.82-7.82c-4.306-0.013-7.806,3.488-7.821,7.82 C72.064,12.222,75.564,15.725,79.87,15.738L79.87,15.738z"/> <path d="M89.759,89.556v-43.19h5.751V22.804c0.007-3.079-2.757-5.448-6.71-5.449H70.436c-3.65,0.001-4.539,1.186-5.551,2.168 L49.597,37.889c-3.098,3.848,2.428,8.333,5.55,4.743L69.88,25.226v64.43c-0.019,6.475,9.06,6.686,9.081,0.201v-36.58h1.765v36.379 C80.748,96.109,89.772,96.13,89.759,89.556L89.759,89.556z"/> <polygon points="100,54.035 100,45.155 0,45.155 0,54.035 100,54.035 "/> </svg> Here’s the XAML that XamlTune created. It can be used in any WPF app without any changes: <Canvas Name="Layer_1" Width="100" Height="94.616" ClipToBounds="True" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"> <Path Fill="#FF000000"> <Path.Data> <PathGeometry FillRule="Nonzero" Figures="M25.076,15.639C29.4,15.648 32.9,12.151 32.896,7.819 32.9,3.512 29.4,0.012 25.076,0 20.763,0.012 17.262,3.512 17.255,7.819 17.262,12.15 20.763,15.648 25.076,15.639L25.076,15.639z" /> </Path.Data> </Path> <Path Fill="#FF000000"> <Path.Data> <PathGeometry FillRule="Nonzero" Figures="M4.593,43.388L11.454,43.388 15.591,28.253 17.307,28.253 13.22,43.388 37.538,43.388 33.149,28.253 34.966,28.253 37.286,35.668C38.366,38.799,41.138,39.519,43.289,36.83L51.664,26.688C54.315,23.268,49.56,19.667,46.82,22.653L41.827,28.605C41.834,28.7 40.867,25.327 40.867,25.327 39.732,21.349 35.949,17.424 30.272,17.405L19.576,17.405C14.505,17.424,10.533,21.839,9.688,24.619L4.593,43.388 4.593,43.388z" /> </Path.Data> </Path> <Path Fill="#FF000000"> <Path.Data> <PathGeometry FillRule="Nonzero" Figures="M56.206,22.753L56.206,7.163 49.192,7.163 49.192,22.753 56.206,22.753z" /> </Path.Data> </Path> <Path Fill="#FF000000"> <Path.Data> <PathGeometry FillRule="Nonzero" Figures="M79.87,15.738C84.202,15.724 87.701,12.222 87.69,7.918 87.701,3.586 84.202,0.0849999999999991 79.87,0.097999999999999 75.564,0.084999999999999 72.064,3.586 72.049,7.918 72.064,12.222 75.564,15.725 79.87,15.738L79.87,15.738z" /> </Path.Data> </Path> <Path Fill="#FF000000"> <Path.Data> <PathGeometry FillRule="Nonzero" Figures="M89.759,89.556L89.759,46.366 95.51,46.366 95.51,22.804C95.517,19.725,92.753,17.356,88.8,17.355L70.436,17.355C66.786,17.356,65.897,18.541,64.885,19.523L49.597,37.889C46.499,41.737,52.025,46.222,55.147,42.632L69.88,25.226 69.88,89.656C69.861,96.131,78.94,96.342,78.961,89.857L78.961,53.277 80.726,53.277 80.726,89.656C80.748,96.109,89.772,96.13,89.759,89.556L89.759,89.556z" /> </Path.Data> </Path> <Path Fill="#FF000000"> <Path.Data> <PathGeometry FillRule="Nonzero" Figures="M100,54.035L100,45.155 0,45.155 0,54.035 100,54.035z" /> </Path.Data> </Path> </Canvas> The XAML works AS-IS in a WPF application but there are some changes I did to get it to work in a WP7 app. Here’s the modified XAML in a WP7 application: <Canvas Grid.Row="0" Grid.Column="0" Name="Icon_1" Width="100" Height="94.616"> <Path Fill="#FF000000" Data="M25.076,15.639C29.4,15.648 32.9,12.151 32.896,7.819 32.9,3.512 29.4,0.012 25.076,0 20.763,0.012 17.262,3.512 17.255,7.819 17.262,12.15 20.763,15.648 25.076,15.639L25.076,15.639z"> </Path> <Path Fill="#FF000000" Data="M4.593,43.388L11.454,43.388 15.591,28.253 17.307,28.253 13.22,43.388 37.538,43.388 33.149,28.253 34.966,28.253 37.286,35.668C38.366,38.799,41.138,39.519,43.289,36.83L51.664,26.688C54.315,23.268,49.56,19.667,46.82,22.653L41.827,28.605C41.834,28.7 40.867,25.327 40.867,25.327 39.732,21.349 35.949,17.424 30.272,17.405L19.576,17.405C14.505,17.424,10.533,21.839,9.688,24.619L4.593,43.388 4.593,43.388z"> </Path> <Path Fill="#FF000000" Data="M56.206,22.753L56.206,7.163 49.192,7.163 49.192,22.753 56.206,22.753z"> </Path> <Path Fill="#FF000000" Data="M79.87,15.738C84.202,15.724 87.701,12.222 87.69,7.918 87.701,3.586 84.202,0.0849999999999991 79.87,0.097999999999999 75.564,0.084999999999999 72.064,3.586 72.049,7.918 72.064,12.222 75.564,15.725 79.87,15.738L79.87,15.738z"> </Path> <Path Fill="#FF000000" Data="M89.759,89.556L89.759,46.366 95.51,46.366 95.51,22.804C95.517,19.725,92.753,17.356,88.8,17.355L70.436,17.355C66.786,17.356,65.897,18.541,64.885,19.523L49.597,37.889C46.499,41.737,52.025,46.222,55.147,42.632L69.88,25.226 69.88,89.656C69.861,96.131,78.94,96.342,78.961,89.857L78.961,53.277 80.726,53.277 80.726,89.656C80.748,96.109,89.772,96.13,89.759,89.556L89.759,89.556z"> </Path> <Path Fill="#FF000000" Data="M100,54.035L100,45.155 0,45.155 0,54.035 100,54.035z"> </Path> </Canvas> All I did was take the data portion and put it directly into a Data attribute on the Path. Note that while it does show up in the app (on the emulator or device) it wouldn’t show up in Visual Studio for me. Maybe some XAML guru out there can tell me why. You can just as easily use the PNG files in WP7 but if you want the crispness of vector graphics, go for the XAML version. Of course with XamlTune being open source you could always modify the output of that program to cater it to your app. If you do make a change that’s worthy please consider submitting a patch to the project so everyone can benefit. Hope this helps and happy programming! Resources and Links Sample Project and Icons XamlTune an open source project to convert SVG to XAML The Noun Project source of the original files Jon Galloways post on SVG and XAML StackOverflow question on converting SVG to XAML

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