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  • printf and Console.WriteLine - problems with Console.SetOut?

    - by Matt Jacobsen
    i have a bunch of Console.WriteLines in my code that I can observe at runtime. I communicate with a native library that I also wrote. I'd like to stick some printf's in the native library and observe them too. I don't see them at runtime however. I've created a convoluted hello world app to demonstrate my problem. When the app runs, I can debug into the native library and see that the hello world is called. The output never lands in the textwriter though. Note that if the same code is run as a console app then everything works fine. C#: [DllImport("native.dll")] static extern void Test(); StreamWriter writer; public Form1() { InitializeComponent(); writer = new StreamWriter(@"c:\output.txt"); writer.AutoFlush = true; System.Console.SetOut(writer); } private void button1_Click(object sender, EventArgs e) { Test(); } and the native part: __declspec(dllexport) void Test() { printf("Hello World"); } Despite my earlier ramblings (see edits) I actually think this is a problem in C# (or rather my understanding of it).

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  • Why This Maintainability Index Increase?

    - by Timothy
    I would be appreciative if someone could explain to me the difference between the following two pieces of code in terms of Visual Studio's Code Metrics rules. Why does the Maintainability Index increase slightly if I don't encapsulate everything within using ( )? Sample 1 (MI score of 71) public static String Sha1(String plainText) { using (SHA1Managed sha1 = new SHA1Managed()) { Byte[] text = Encoding.Unicode.GetBytes(plainText); Byte[] hashBytes = sha1.ComputeHash(text); return Convert.ToBase64String(hashBytes); } } Sample 2 (MI score of 73) public static String Sha1(String plainText) { Byte[] text, hashBytes; using (SHA1Managed sha1 = new SHA1Managed()) { text = Encoding.Unicode.GetBytes(plainText); hashBytes = sha1.ComputeHash(text); } return Convert.ToBase64String(hashBytes); } I understand metrics are meaningless outside of a broader context and understanding, and programmers should exercise discretion. While I could boost the score up to 76 with return Convert.ToBase64String(sha1.ComputeHash(Encoding.Unicode.GetBytes(plainText))), I shouldn't. I would clearly be just playing with numbers and it isn't truly any more readable or maintainable at that point. I am curious though as to what the logic might be behind the increase in this case. It's obviously not line-count.

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  • Building a News-feed that comprises posts "created by user's connections" && "on the topics user is following"

    - by aklin81
    I am working on a project of Questions & Answers website that allows a user to follow questions on certain topics from his network. A user's news-feed wall comprises of only those questions that have been posted by his connections and tagged on the topics that he is following(his expertise topics). I am confused what database's datamodel would be most fitting for such an application. The project needs to consider the future provisions for scalability and high performance issues. I have been looking at Cassandra and MySQL solutions as of now. After my study of Cassandra I realized that Simple news-feed design that shows all the posts from network would be easy to design using Cassandra by executing fast writes to all followers of a user about the post from user. But for my kind of application where there is an additional filter of 'followed topics', (ie, the user receives posts "created by his network" && "on topics user is following"), I could not convince myself with a good schema design in Cassandra. I hope if I missed something because of my short understanding of cassandra, perhaps, can you please help me out with your suggestions of how this news-feed could be implemented in Cassandra ? Looking for a great project with Cassandra ! Edit: There are going to be maximum 5 tags allowed for tagging the question (ie, max 5 topics can be tagged on a question).

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  • Is ASP.NET MVC is really MVC? Or how to separate model from controller?

    - by Andrey
    Hi all, This question is a bit rhetorical. At some point i got a feeling that ASP.NET MVC is not that authentic implementation of MVC pattern. Or i didn't understood it. Consider following domain: electric bulb, switch and motion detector. They are connected together and when you enter the room motion detector switches on the bulb. If i want to represent them as MVC: switch is model, because it holds the state and contains logic bulb is view, because it presents the state of model to human motion detector is controller, because it converts user actions to generic model commands Switch has one private field (On/Off) as a State and two methods (PressOn, PressOff). If you call PressOn when it is Off it goes to On, if you call it again state doesn't change. Bulb can be replaced with buzzer, motion detector with timer or button, but the model still represent the same logic. Eventually system will have same behavior. This is how i understand classical MVC decomposition, please correct me if i am wrong. Now let's decompose it in ASP.Net MVC way. Bulb is still a view Controller will be switch + motion detector Model is some object that will just pass state to bulb. So the logic that defines behavior moves to controller. Question 1: Is my understanding of MVC and ASP.NET MVC correct? Question 2: If yes, do you agree that ASP.NET MVC is not 100% accurate implementation? And back to life. The final question is how to separate model from controller in case of ASP.NET MVC. There can be two extremes. Controller does basic stuff and call model to do all the logic. Another is controller does all the logic and model is just something like class with properties that is mapped to DB. Question 3: Where should i draw the line between this extremes? How to balance? Thanks, Andrey

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  • Authenticating GTK app to run with root permissions

    - by Thomas Tempelmann
    I have a UI app (uses GTK) for Linux that requires to be run as root (it reads and writes /dev/disk*). Instead of requiring the user to open a root shell or use "sudo" manually every time when he launches my app, I wonder if the app can use some OS-provided API to ask the user to relaunch the app with root permissions. (Note: gtk app's can't use "setuid" mode, so that's not an option here.) The advantage here would be an easier workflow: The user could, from his default user account, double click my app from the desktop, and the app then would relaunch itself with root permission after been authenticated by the API/OS. I ask this because OS X offers exactly this: An app can ask the OS to launch an executable with root permissions - the OS (and not the app) then asks the user to input his credentials, verifies them and then launches the target as desired. I wonder if there's something similar for Linux (Ubuntu, e.g.) Update: The app is a remote operated disk repair tool for the unsavvy Linux user, and those Linux noobs won't have much understanding of using sudo or even changing their user's group memberships, especially if their disk just started acting up and they're freaking out. That's why I seek a solution that avoids technicalities like this.

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  • Binding a date string parameter in an MS Access PDO query

    - by harryg
    I've made a PDO database class which I use to run queries on an MS Access database. When querying using a date condition, as is common in SQL, dates are passed as a string. Access usually expects the date to be surrounded in hashes however. E.g. SELECT transactions.amount FROM transactions WHERE transactions.date = #2013-05-25#; If I where to run this query using PDO I might do the following. //instatiate pdo connection etc... resulting in a $db object $stmt = $db->prepare('SELECT transactions.amount FROM transactions WHERE transactions.date = #:mydate#;'); //prepare the query $stmt->bindValue('mydate', '2013-05-25', PDO::PARAM_STR); //bind the date as a string $stmt->execute(); //run it $result = $stmt->fetch(); //get the results As far as my understanding goes the statement that results from the above would look like this as binding a string results in it being surrounded by quotes: SELECT transactions.amount FROM transactions WHERE transactions.date = #'2013-05-25'#; This causes an error and prevents the statement from running. What's the best way to bind a date string in PDO without causing this error? I'm currently resorting to sprintf-ing the string which I'm sure is bad practise. Edit: if I pass the hash-surrounded date then I still get the error as below: Fatal error: Uncaught exception 'PDOException' with message 'SQLSTATE[22018]: Invalid character value for cast specification: -3030 [Microsoft][ODBC Microsoft Access Driver] Data type mismatch in criteria expression. (SQLExecute[-3030] at ext\pdo_odbc\odbc_stmt.c:254)' in C:\xampp\htdocs\ips\php\classes.php:49 Stack trace: #0 C:\xampp\htdocs\ips\php\classes.php(49): PDOStatement-execute() #1 C:\xampp\htdocs\ips\php\classes.php(52): database-execute() #2 C:\xampp\htdocs\ips\try2.php(12): database-resultset() #3 {main} thrown in C:\xampp\htdocs\ips\php\classes.php on line 49

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  • Neural Network with softmax activation

    - by Cambium
    This is more or less a research project for a course, and my understanding of NN is very/fairly limited, so please be patient :) ============== I am currently in the process of building a neural network that attempts to examine an input dataset and output the probability/likelihood of each classification (there are 5 different classifications). Naturally, the sum of all output nodes should add up to 1. Currently, I have two layers, and I set the hidden layer to contain 10 nodes. I came up with two different types of implementations 1) Logistic sigmoid for hidden layer activation, softmax for output activation 2) Softmax for both hidden layer and output activation I am using gradient descent to find local maximums in order to adjust the hidden nodes' weights and the output nodes' weights. I am certain in that I have this correct for sigmoid. I am less certain with softmax (or whether I can use gradient descent at all), after a bit of researching, I couldn't find the answer and decided to compute the derivative myself and obtained softmax'(x) = softmax(x) - softmax(x)^2 (this returns an column vector of size n). I have also looked into the MATLAB NN toolkit, the derivative of softmax provided by the toolkit returned a square matrix of size nxn, where the diagonal coincides with the softmax'(x) that I calculated by hand; and I am not sure how to interpret the output matrix. I ran each implementation with a learning rate of 0.001 and 1000 iterations of back propagation. However, my NN returns 0.2 (an even distribution) for all five output nodes, for any subset of the input dataset. My conclusions: o I am fairly certain that my gradient of descent is incorrectly done, but I have no idea how to fix this. o Perhaps I am not using enough hidden nodes o Perhaps I should increase the number of layers Any help would be greatly appreciated! The dataset I am working with can be found here (processed Cleveland): http://archive.ics.uci.edu/ml/datasets/Heart+Disease

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  • how to push a string address to stack with assembly, machine code

    - by Yigit
    Hi all, I am changing minesweeper.exe in order to have an understanding of how code injection works. Simply, I want the minesweeper to show a message box before starting. So, I find a "cave" in the executable and then define the string to show in messagebox and call the messagebox. Additionally of course, I have to change the value at module entry point of the executable and first direct it to my additional code, then continue its own code. So at the cave what I do; "hello starbuck",0 push 0 //arg4 of MessageBoxW function push the address of my string //arg3, must be title push the address of my string //arg2, must be the message push 0 //arg1 call MessageBoxW ... Now since the memory addresses of codes in the executable change everytime it is loaded in the memory, for calling the MessageBoxW function, I give the offset of the address where MessageBoxW is defined in Import Address Table. For instance, if MessageBoxW is defined at address1 in the IAT and the instruction just after call MessageBoxW is at address2 instead of writing call MessageBoxW, I write call address2 - address1. So my question is, how do I do it for pushing the string's address to the stack? For example, if I do these changes via ollydbg, I give the immediate address of "hello starbuck" for pushing and it works. But after reloading the executable or starting it outside of ollydbg, it naturally fails, since the immediate addresses change. Thanks in advance, Yigit.

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  • Integer Surrogate Key?

    - by CitadelCSAlum
    I need something real simple, that for some reason I am unable to accomplish to this point. I have also been unable to Google the answer surprisingly. I need to number the entries in different tables uniquely. I am aware of AUTO INCREMENT in MySQL and that it will be involved. My situation would be as follows If I had a table like Table EXAMPLE ID - INTEGER FIRST_NAME - VARCHAR(45) LAST_NAME - VARCHAR(45) PHONE - VARCHAR(45) CITY - VARCHAR(45) STATE - VARCHAR(45) ZIP - VARCHAR(45) This would be the setup for the table where ID is an integer that is auto-incremented every time an entry is inserted into the table. The thing I need is that I do not want to have to account for this field when inserting data into the database. From my understanding this would be a surrogate key, that I can tell the database to automatically increment and I do not have to include it in the INSERT STATEMENT so instead of INSERT INTO EXAMPLE VALUES (2,'JOHN','SMITH',333-333-3333,'NORTH POLE'.... I can leave out the first ID column and just write something like INSERT INTO EXAMPLE VALUES ('JOHN','SMITH'.....etc) Notice I Wouldnt have to define the ID column... I know this is a very common task to do, but for some reason I cant get to the bottom of it. I am using MySQL, just to clarify. Thanks alot

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  • Nginx rewrite for link shortener and Wordpress

    - by detusueno
    I'm a complete newbie to Nginx, so much so that I followed a online guide to do most of my server setup. I'm trying to learn but I'm still a ways away from understanding it all. So what I'm trying to create is a link shortener that redirects (example.com/x) to (example.com/short.php?id=x). Keep in mind that I'm also running a Wordpress blog on the same domain and plan on using the redirects/shortening for external links. The guide has so far had me add the following rewrites to enable Wordpress pretty URLs: # WordPress pretty URLs: (as per dominiek.com) if (-f $request_filename) { break; } if (-d $request_filename) { break; } rewrite ^(.+)$ /index.php?q=$1 last; # Enable nice permalinks for WordPress: (as per Yawn.it) error_page 404 = //index.php?q=$uri; And if it matters any, it was saved at (/usr/local/nginx/conf/wordpress_params.regular). Additionally, my Wordpress link structure adds "news" to all internal links (example.com/news/post-blah, example.com/news/category, ect.). What's the best way to tackle this setup?

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  • JQuery Deferred - Adding to the Deferred contract

    - by MgSam
    I'm trying to add another asynchronous call to the contract of an existing Deferred before its state is set to success. Rather than try and explain this in English, see the following pseudo-code: $.when( $.ajax({ url: someUrl, data: data, async: true, success: function (data, textStatus, jqXhr) { console.log('Call 1 done.') jqXhr.pipe( $.ajax({ url: someUrl, data: data, async: true, success: function (data, textStatus, jqXhr) { console.log('Call 2 done.'); }, }) ); }, }), $.ajax({ url: someUrl, data: data, async: true, success: function (data, textStatus, jqXhr) { console.log('Call 3 done.'); }, }) ).then(function(){ console.log('All done!'); }); Basically, Call 2 is dependent on the results of Call 1. I want Call 1 and Call 3 to be executed in parallel. Once all 3 calls are complete, I want the All Done code to execute. My understanding is that Deferred.pipe() is supposed to chain another asynchronous call to the given deferred, but in practice, I always get Call 2 completing after All Done. Does anyone know how to get jQuery's Deferred to do what I want? Hopefully the solution doesn't involve ripping the code apart into chunks any further. Thanks for any help.

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  • c# web extracting programming, which libraries, examples samples please

    - by user287745
    I have just started programming and have made a few small applications in C and C#. My understanding is that programming for web and thing related to web is nowadays a very easy task. Please note this is for personnel learning, not for rent a coder or any money making. An application which can run on any Windows platform even Windows 98. The application should start automatically at a scheduled time and do the following. Connect to a site which displays stock prices summary (high low current open). Capture the data (excluding the other things in the site.) And save it to disk (an SQL database) Please note:- Internet connection is assumed to be there always. Do not want to know how to make database schema or database. The stock exchange has no law prohibiting the use of the data provided on its site, but I do not want to mention the name in case I am wrong, but it's for personal private use only. The data of summary of pricing is arranged in a table such that when copied pasted to MS Excel it automatically forms a table. need steps guidance please, examples, lbraries

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  • JQuery UI Tabs: Apply opacity toggle to only specific inner element?

    - by Kerri
    I am using Jquery UI tabs, and have it set to toggle the opacity with each slide change. I'm wondering if there's a way to apply the opacity toggle to only a single element within each tab, instead of the entire tab. My understanding of jQuery is pretty basic, so bear with me. So, If I have something like this: <div id="tabs"> <ul id="tabs-nav><li></li></ul> <div id="tab-1"> <img /> <p /> </div> <div id="tab-2"> <img /> <p /> </div> ...etc </div> How could I set it so that only the <img> has an effect applied, and the rest just switches normally? Here are the basics of the call I have for UI tabs: var $tabs = $('#slides').tabs({fx: { opacity: 'toggle' } }); $(".ui-tabs-panel").each(function(i){ //stuff to create previous/next links }); $('.next-tab, .prev-tab').click(function() { $tabs.tabs('select', $(this).attr("rel")); return false; });

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  • randomized quicksort: probability of two elements comparison?

    - by bantu
    I am reading "Probability and Computing" by M.Mitzenmacher, E.Upfal and I have problems understanding how the probability of comparison of two elements is calculated. Input: the list (y1,y2,...,YN) of numbers. We are looking for pivot element. Question: what is probability that two elements yi and yj (ji) will be compared? Answer (from book): yi and yj will be compared if either yi or yj will be selected as pivot in first draw from sequence (yi,yi+1,...,yj-1,yj). So the probablity is: 2/(y-i+1). The problem for me is initial claim: for example, picking up yi in the first draw from the whole list will cause the comparison with yj (and vice-versa) and the probability is 2/n. So, rather the "reverse" claim is true -- none of the (yi+1,...,yj-1) elements can be selected beforeyi or yj, but the "pool" size is not fixed (in first draw it is n for sure, but on the second it is smaller). Could someone please explain this, how the authors come up with such simplified conclusion? Thank you in advance

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  • Delphi 6 OleServer.pas Invoke memory leak

    - by Mike Davis
    There's a bug in delphi 6 which you can find some reference online for when you import a tlb the order of the parameters in an event invocation is reversed. It is reversed once in the imported header and once in TServerEventDIspatch.Invoke. you can find more information about it here: http://cc.embarcadero.com/Item/16496 somewhat related to this issue there appears to be a memory leak in TServerEventDispatch.Invoke with a parameter of a Variant of type Var_Array (maybe others, but this is the more obvious one i could see). The invoke code copies the args into a VarArray to be passed to the event handler and then copies the VarArray back to the args after the call, relevant code pasted below: // Set our array to appropriate length SetLength(VarArray, ParamCount); // Copy over data for I := Low(VarArray) to High(VarArray) do VarArray[I] := OleVariant(TDispParams(Params).rgvarg^[I]); // Invoke Server proxy class if FServer <> nil then FServer.InvokeEvent(DispID, VarArray); // Copy data back for I := Low(VarArray) to High(VarArray) do OleVariant(TDispParams(Params).rgvarg^[I]) := VarArray[I]; // Clean array SetLength(VarArray, 0); There are some obvious work-arounds in my case: if i skip the copying back in case of a VarArray parameter it fixes the leak. to not change the functionality i thought i should copy the data in the array instead of the variant back to the params but that can get complicated since it can hold other variants and seems to me that would need to be done recursively. Since a change in OleServer will have a ripple effect i want to make sure my change here is strictly correct. can anyone shed some light on exactly why memory is being leaked here? I can't seem to look up the callstack any lower than TServerEventDIspatch.Invoke (why is that?) I imagine that in the process of copying the Variant holding the VarArray back to the param list it added a reference to the array thus not allowing it to be release as normal but that's just a rough guess and i can't track down the code to back it up. Maybe someone with a better understanding of all this could shed some light?

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  • Obtaining touch location for a uiscrollview touch

    - by LOSnively
    I have a uiscrollview as an element of a uiscrollviewcontroller, along with other view objects. The image scrolls and zooms as expected, when the scrollView is the top subview. However, I also need to get the screen location of the touch, in particular when there is no scroll action. (I understand the location may change during a scroll, but that's not important.) I haven't found a way to do that. In the scrollviewcontroller implementation I have customized all of the standard methods that should do this: "touchesShouldBegin...", "touchesBegan:...", "touchesEnded:...", and so on. As far as I can tell, none of these are being called during a touch event when the scrollView is the top subview. I've tried setting the delayContentTouches property to both YES and NO, and that doesn't seem to make a difference. As an alternative, I've tried putting a UIView as the top subview and then tried passing the touches to the now underlying scrollView. In this configuration, the standard methods are called and I can get the touch location, but I haven't found a mechanism for the touches to be passed to the scrollView so scrolling occurs. Doing something like sending the touch messages to the specific scrollView, or to "super" or just sending them to nextResponder doesn't do it. It seems I can make the scroll work or find the location of the touch but not both, depending on what the "top" subview is. I suspect this is trivial, but after two weeks of struggling, it's time to eat my embarrassment for not being able to do this seemingly simplest of things. I've read all of the related questions here on stackoverflow, tried most if not all of the suggestions, and so far, nothing has worked. I've looked through the various links and references suggested by the answers, including Apple's documentation, but none have pointed out the gap in my understanding. Any ideas would be appreciated.

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  • RESTful design, how to name pages outside CRUD et al?

    - by sscirrus
    Hi all, I'm working on a site that has quite a few pages that fall outside my limited understanding of RESTful design, which is essentially: Create, Read, Update, Delete, Show, List Here's the question: what is a good system for labeling actions/routes when a page doesn't neatly fall into CRUD/show/list? Some of my pages have info about multiple tables at once. I am building a site that gives some customers a 'home base' after they log on. It does NOT give them any information about themselves so it shouldn't be, for example, /customers/show/1. It does have information about companies, but there are other pages on the site that do that differently. What do you do when you have these situations? This 'home-base' is shown to customers and it mainly has info about companies (but not uniquely so). Second case: I have a table called 'Matchings' in between customers and companies. These matchings are accessed in completely different ways on different parts of the site (different layouts, different CSS sheets, different types of users accessing them, etc. They can't ALL be matchings/show. What's the best way to label the others? Thanks very much. =)

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  • Question about the Cloneable interface and the exception that should be thrown

    - by Nazgulled
    Hi, The Java documentation says: A class implements the Cloneable interface to indicate to the Object.clone() method that it is legal for that method to make a field-for-field copy of instances of that class. Invoking Object's clone method on an instance that does not implement the Cloneable interface results in the exception CloneNotSupportedException being thrown. By convention, classes that implement this interface should override Object.clone (which is protected) with a public method. See Object.clone() for details on overriding this method. Note that this interface does not contain the clone method. Therefore, it is not possible to clone an object merely by virtue of the fact that it implements this interface. Even if the clone method is invoked reflectively, there is no guarantee that it will succeed. And I have this UserProfile class: public class UserProfile implements Cloneable { private String name; private int ssn; private String address; public UserProfile(String name, int ssn, String address) { this.name = name; this.ssn = ssn; this.address = address; } public UserProfile(UserProfile user) { this.name = user.getName(); this.ssn = user.getSSN(); this.address = user.getAddress(); } // get methods here... @Override public UserProfile clone() { return new UserProfile(this); } } And for testing porpuses, I do this in main(): UserProfile up1 = new UserProfile("User", 123, "Street"); UserProfile up2 = up1.clone(); So far, no problems compiling/running. Now, per my understanding of the documentation, removing implements Cloneable from the UserProfile class should throw an exception in up1.clone() call, but it doesn't. I've read around here that the Cloneable interface is broken but I don't really know what that means. Am I missing something?

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  • Linear feedback shift register?

    - by Mattia Gobbi
    Lately I bumped repeatedly into the concept of LFSR, that I find quite interesting because of its links with different fields and also fascinating in itself. It took me some effort to understand, the final help was this really good page, much better than the (at first) cryptic wikipedia entry. So I wanted to write some small code for a program that worked like a LFSR. To be more precise, that somehow showed how a LFSR works. Here's the cleanest thing I could come up with after some lenghtier attempts (Python): def lfsr(seed, taps): sr, xor = seed, 0 while 1: for t in taps: xor += int(sr[t-1]) if xor%2 == 0.0: xor = 0 else: xor = 1 print xor sr, xor = str(xor) + sr[:-1], 0 print sr if sr == seed: break lfsr('11001001', (8,7,6,1)) #example I named "xor" the output of the XOR function, not very correct. However, this is just meant to show how it circles through its possible states, in fact you noticed the register is represented by a string. Not much logical coherence. This can be easily turned into a nice toy you can watch for hours (at least I could :-) def lfsr(seed, taps): import time sr, xor = seed, 0 while 1: for t in taps: xor += int(sr[t-1]) if xor%2 == 0.0: xor = 0 else: xor = 1 print xor print time.sleep(0.75) sr, xor = str(xor) + sr[:-1], 0 print sr print time.sleep(0.75) Then it struck me, what use is this in writing software? I heard it can generate random numbers; is it true? how? So, it would be nice if someone could: explain how to use such a device in software development come up with some code, to support the point above or just like mine to show different ways to do it, in any language Also, as theres not much didactic stuff around about this piece of logic and digital circuitry, it would be nice if this could be a place for noobies (like me) to get a better understanding of this thing, or better, to understand what it is and how it can be useful when writing software. Should have made it a community wiki? That said, if someone feels like golfing... you're welcome.

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  • HttpURLConnection: What's the deal with having to read the whole response?

    - by stormin986
    My current problem is very similar to this one. I have a downloadFile(URL) function that creates a new HttpURLConnection, opens it, reads it, returns the results. When I call this function on the same URL multiple times, the second time around it almost always returns a response code of -1 (But throws no exception!!!). The top answer in that question is very helpful, but there are a few things I'm trying to understand. So, if setting http.keepAlive to false solves the problem, it indicates what exactly? That the server is responding in a way that violates the http protocol? Or more likely, my code is violating the protocol in some way? What will the trace tell me? What should I look for? And what's the deal with this: You need to read everything from error stream. Otherwise, it's going to confuse next connection and that's the cause of -1. Does this mean if the response is some type of error (which would be what response code(s)?), the stream HAS to be fully read? Also, every time I am attempting an http request I am basically creating a new connection, and then disconnect()ing it at the end. However, in my case I'm not getting a 401 or whatever. It's always a 200. But my second connection almost always fails. Does this mean there's some other data I should be reading that I'm not (in a similar manner that the error stream must be fully read)? Please help shed some light on this? I feel like there's some fundamental http protocol understanding I'm missing.

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  • Using pipes in Linux with C

    - by Dave
    Hi, I'm doing a course in Operating Systems and we're supposed to learn how to use pipes to transfer data between processes. We were given this simple piece of code which demonstrates how to use pipes,but I'm having difficulty understanding it. #include <stdio.h> #include <stdlib.h> #include <unistd.h> main() { int pipefd [2], n; char buff[100] ; if( pipe( pipefd) < 0) { printf("can not create pipe \n"); } printf("read fd = %d, write fd = %d \n", pipefd[0], pipefd[1]); if ( write (pipefd[1],"hello world\n", 12)!= 12) { printf("pipe write error \n"); } if( ( n = read ( pipefd[0] , buff, sizeof ( buff) ) ) <= 0 ) { printf("pipe read error \n"); } write ( 1, buff, n ) ; exit (0); } What does the write function do? It seems to send data to the pipe and also print it to the screen (at least it seems like the second time the write function is called it does this). Does anyone have any suggestions of good websites for learning about topics such as this, FIFO, signals, other basic linux commands used in C?

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  • How to pass parameters to manage_shared_memory.construct() in Boost.Interprocess

    - by recipriversexclusion
    I've stared at the Boost.Interprocess documentation for hours but still haven't been able to figure this out. In the doc, they have an example of creating a vector in shared memory like so: //Define an STL compatible allocator of ints that allocates from the managed_shared_memory. //This allocator will allow placing containers in the segment typedef allocator<int, managed_shared_memory::segment_manager> ShmemAllocator; //Alias a vector that uses the previous STL-like allocator so that allocates //its values from the segment typedef vector<int, ShmemAllocator> MyVector; int main(int argc, char *argv[]) { //Create a new segment with given name and size managed_shared_memory segment(create_only, "MySharedMemory", 65536); //Initialize shared memory STL-compatible allocator const ShmemAllocator alloc_inst (segment.get_segment_manager()); //Construct a vector named "MyVector" in shared memory with argument alloc_inst MyVector *myvector = segment.construct<MyVector>("MyVector")(alloc_inst); Now, I understand this. What I'm stuck is how to pass a second parameter to segment.construct() to specify the number of elements. The interprocess document gives the prototype for construct() as MyType *ptr = managed_memory_segment.construct<MyType>("Name") (par1, par2...); but when I try MyVector *myvector = segment.construct<MyVector>("MyVector")(100, alloc_inst); I get compilation errors. My questions are: Who actually gets passed the parameters par1, par2 from segment.construct, the constructor of the object, e.g. vector? My understanding is that the template allocator parameter is being passed. Is that correct? How can I add another parameter, in addition to alloc_inst that is required by the constructor of the object being created in shared memory? There's very little information other than the terse Boost docs on this.

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  • JPA @ManyToMany on only one side?

    - by Ethan Leroy
    I am trying to refresh the @ManyToMany relation but it gets cleared instead... My Project class looks like this: @Entity public class Project { ... @ManyToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER) @JoinTable(name = "PROJECT_USER", joinColumns = @JoinColumn(name = "PROJECT_ID", referencedColumnName = "ID"), inverseJoinColumns = @JoinColumn(name = "USER_ID", referencedColumnName = "ID")) private Collection<User> users; ... } But I don't have - and I don't want - the collection of Projects in the User entity. When I look at the generated database tables, they look good. They contain all columns and constraints (primary/foreign keys). But when I persist a Project that has a list of Users (and the users are still in the database), the mapping table doesn't get updated gets updated but when I refresh the project afterwards, the list of Users is cleared. For better understanding: Project project = ...; // new project with users that are available in the db System.out.println(project getUsers().size()); // prints 5 em.persist(project); System.out.println(project getUsers().size()); // prints 5 em.refresh(project); System.out.println(project getUsers().size()); // prints 0 So, how can I refresh the relation between User and Project?

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  • How to write a custom solution using a python package, modules etc

    - by morpheous
    I am writing a packacge foobar which consists of the modules alice, bob, charles and david. From my understanding of Python packages and modules, this means I will create a folder foobar, with the following subdirectories and files (please correct if I am wrong) foobar/ __init__.py alice/alice.py bob/bob.py charles/charles.py david/david.py The package should be executable, so that in addition to making the modules alice, bob etc available as 'libraries', I should also be able to use foobar in a script like this: python foobar --args=someargs Question1: Can a package be made executable and used in a script like I described above? Question 2 The various modules will use code that I want to refactor into a common library. Does that mean creating a new sub directory 'foobar/common' and placing common.py in that folder? Question 3 How will the modules foo import the common module ? Is it 'from foobar import common' or can I not use this since these modules are part of the package? Question 4 I want to add logic for when the foobar package is being used in a script (assuming this can be done - I have only seen it done for modules) The code used is something like: if __name__ == "__main__": dosomething() where (in which file) would I put this logic ?

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  • How Can I: Generate 40/64 Bit WEP Key In Python?

    - by Aktariel
    So, I've been beating my head against the wall of this issue for several months now, partly because it's a side interest and partly because I suck at programming. I've searched and researched all across the web, but have not had any luck (except one small bit of success; see below), so I thought I might try asking the experts. What I am trying to do is, as the title suggests, generate a 40/64 bit WEP key from a passphrase, according to the "de facto" standard. (A site such as [http://www.powerdog.com/wepkey.cgi] produces the expected outputs.) I have already written portions of the script that take inputs and write them to a file; one of the inputs would be the passphrase, sanitized to lower case. For the longest time I had no idea what the defacto standard was, much less how to even go about implementing it. I finally stumbled across a paper (http://www.lava.net/~newsham/wlan/WEP_password_cracker.pdf) that sheds as much light as I've had yet on the issue (page 18 has the relevant bits). Apparently, the passphrase is "mapped to a 32-bit value with XOR," the result of which is then used as the seed for a "linear congruential PRNG (which one of the several PRNGs Python has would fit this description, I don't know), and then from that result several bits of the result are taken. I have no idea how to go about implementing this, since the description is rather vague. What I need is help in writing the generator in Python, and also in understanding how exactly the key is generated. I'm not much of a programmer, so explanations are appreciated as well. (Yes, I know that WEP isn't secure.)

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