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  • Consulting a Prolog Source Code from within a VS2008 Solution File

    - by Joshua Green
    I have a Prolog file (Hanoi.pl) containing the code for solving the Hanoi Towers puzzle: hanoi( N ):- move( N, left, middle, right ). move( 0, _, _, _ ):- !. move( N, A, B, C ):- M is N-1, move( M, A, C, B ), inform( A, B ), move( M, C, B, A ). inform( X, Y ):- write( 'move a disk from ' ), write( X ), write( ' to ' ), writeln( Y ). I also have a C++ file written in VS2008 IDE: #include <iostream> #include <string> #include <stdio.h> #include <stdlib.h> using namespace std; #include "SWI-cpp.h" #include "SWI-Prolog.h" predicate_t phanoi; term_t t0; int main(int argc, char** argv) { long n = 5; int rval; if ( !PL_initialise(1, argv) ) PL_halt(1); PL_put_integer( t0, n ); phanoi = PL_predicate( "hanoi", 1, NULL ); rval = PL_call_predicate( NULL, PL_Q_NORMAL, phanoi, t0 ); system( "PAUSE" ); } How can I consult my Prolog source code (Hanoi.pl) from within my C++ code? Not from the Command Prompt - from the code, something like include or consult or compile? It is located in the same folder as my cpp file. Thanks,

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  • How to learn how to program?

    - by twinbornJoint
    I would like to know the best methods for learning to program. I've been directed towards the Python language because I was told it is good for beginners. I ultimately want to make games for OS X/iPhone. My problem is that I understand what I read but I can't apply my knowledge to anything. I am a programming noob. Should I stick with Python? (is there a better language I should be learning?) Where can I learn programming theory? I get very hyper when reading my book sometimes, any tips on staying calm and focusing? What are effective ways to learn how to program? Are there standard exercises for programming? (I feel solving problems helps my understanding immensely) Ultimately I feel like I am in a never ending tunnel that leads me no where. It feels like I am just completely unable to pursue anything in the world of programming, yet it is something I want to do very much. Thanks.

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  • Login problem with php

    - by shinod
    I want to prevent multiple log in with same log in credentials simultaneously. So I made a column login_status and set it to 1 when some one logging in and change to 0 when logging out besides I set session after successful logged in. If user won't click on log out(in case of user close tab or because of some network problem) it doesn't update database and then one can't use that log in credentials again. So I use a ajax call to set current time stamp in database with related log in credentials and it is updated in each 2 minutes if user not navigate from that page. Then if some one attempts to log in with same log in credentials, it will check these time stamp if column login_status is 1, then if the time stamp is older than 3 minutes it allows the log in.Then it solving that problem. But the new problem is if user closes the tab or browser window and after 3 minutes one can log in with same log in credentials from somewhere and if the previous user open that page automatically it will log in as session is already set. How can I prevent this.

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  • Simplest PHP Routing framework .. ?

    - by David
    I'm looking for the simplest implementation of a routing framework in PHP, in a typical PHP environment (Running on Apache, or maybe nginx) .. It's the implementation itself I'm mostly interested in, and how you'd accomplish it. I'm thinking it should handle URL's, with the minimal rewriting possible, (is it really a good idea, to have the same entrypoint for all dynamic requests?!), and it should not mess with the querystring, so I should still be able to fetch GET params with $_GET['var'] as you'd usually do.. So far I have only come across .htaccess solutions that puts everything through an index.php, which is sort of okay. Not sure if there are other ways of doing it. How would you "attach" what URL's fit to what controllers, and the relation between them? I've seen different styles. One huge array, with regular expressions and other stuff to contain the mapping. The one I think I like the best is where each controller declares what map it has, and thereby, you won't have one huge "global" map, but a lot of small ones, each neatly separated. So you'd have something like: class Root { public $map = array( 'startpage' => 'ControllerStartPage' ); } class ControllerStartPage { public $map = array( 'welcome' => 'WelcomeControllerPage' ); } // Etc ... Where: 'http://myapp/' // maps to the Root class 'http://myapp/startpage' // maps to the ControllerStartPage class 'http://myapp/startpage/welcome' // maps to the WelcomeControllerPage class 'http://myapp/startpage/?hello=world' // Should of course have $_GET['hello'] == 'world' What do you think? Do you use anything yourself, or have any ideas? I'm not interested in huge frameworks already solving this problem, but the smallest possible implementation you could think of. I'm having a hard time coming up with a solution satisfying enough, for my own taste. There must be something pleasing out there that handles a sane bootstrapping process of a PHP application without trying to pull a big magic hat over your head, and force you to use "their way", or the highway! ;)

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  • Detecting one point's location compared to two other points.

    - by WizardOfOdds
    Hi all, you can check my profile, this is not homework. I've got an interesting little problem to solve in a very real software and I'm looking for an easy way to solve it. I've got two fixed points on screen (they're fixed, but I don't know beforehand their position) that are not at the same location. These two fixed points form an imaginary line. Now I've got a third point that is "on one side" of that line (it cannot be on the line). The user can grab the point (the user actually grab an object, whose I track by its center, which is the point I'm interested in) and drag it. But it cannot "cross" the imaginary line. What is the easiest way to detect if the user is crossing the imaginary line? Example: a c / / (c cannot be dragged here) / b Or: c b -------------- a (c cannot be dragged here) So what is an easy to detect if c is staying on the correct "side" of the line (I draw segments here, but it really can be thought of as a line). One way to detect this is to take the destination point d and see if segment (c,d) intersects with line (a,b), but isn't there an easier way? Can't I just do some 2D dot-product magic here and have basically a one or two liner solving my issue?

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  • World's Most Challening MySQL SQL Query (least I think so...)

    - by keruilin
    Whoever answers this question can claim credit for solving the world's most challenging SQL query, according to yours truly. Working with 3 tables: users, badges, awards. Relationships: user has many awards; award belongs to user; badge has many awards; award belongs to badge. So badge_id and user_id are foreign keys in the awards table. The business logic at work here is that every time a user wins a badge, he/she receives it as an award. A user can be awarded the same badge multiple times. Each badge is assigned a designated point value (point_value is a field in the badges table). For example, BadgeA can be worth 500 Points, BadgeB 1000 Points, and so on. As further example, let's say UserX won BadgeA 10 times and BadgeB 5 times. BadgeA being worth 500 Points, and BadgeB being worth 1000 Points, UserX has accumulated a total of 10,000 Points ((10 x 500) + (5 x 1000)). The end game here is to return a list of top 50 users who have accumulated the most badge points. Can you do it?

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  • Help with PHP simplehtmldom - Modifiying a form.

    - by onemyndseye
    Ive gotten some great help here and I am so close to solving my problem that I can taste it. But I seem to be stuck. I need to scrape a simple form from a local webserver and only return the lines that match a users local email (i.e. onemyndseye@localhost). simplehtmldom makes easy work of extracting the correct form element: foreach($html->find('form[action*="delete"]') as $form) echo $form; Returns: <form action="/delete" method="post"> <input type="checkbox" id="D1" name="D1" /><a href="http://www.linux.com/rss/feeds.php"> http://www.linux.com/rss/feeds.php </a> [email: onemyndseye@localhost (Default) ]<br /> <input type="checkbox" id="D2" name="D2" /><a href="http://www.ubuntu.com/rss.xml"> http://www.ubuntu.com/rss.xml </a> [email: onemyndseye@localhost (Default) ]<br /> However I am having trouble making the next step. Which is returning lines that contain 'onemyndseye@localhost' and removing it so that only the following is returned: <input type="checkbox" id="D1" name="D1" /><a href="http://www.linux.com/rss/feeds.php">http://www.linux.com/rss/feeds.php</a> <br /> <input type="checkbox" id="D2" name="D2" /><a href="http://www.ubuntu.com/rss.xml">http://www.ubuntu.com/rss.xml</a> <br /> Thanks to the wonderful users of this site Ive gotten this far and can even return just the links but I am having trouble getting the rest... Its important that the complete <input> tags are returned EXACTLY as shown above as the id and name values will need to be passed back to the original form in post data later on. Thanks in advance!

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  • Stage untracked files for commit without staging tracked file changes

    - by Blair Holloway
    Oftentimes, when using git, I find myself in this situation: I have changes to several files, but I only want to commit parts of them. I have added several untracked files, which I want to track and commit. Solving the first part is easy; I run: git add -p Then, I choose which hunks to stage, and which hunks remain in my working tree, but unstaged. However, git's patch mode skips over untracked files. What I would like to do is something like: git add --untracked But no such option appears to exist. If I have, say, six untracked files, I could stage them using add in interactive mode and the add untracked option, like so: git add -i a<CR> 1<CR> 2<CR> 3<CR> 4<CR> 5<CR> 6<CR> <CR> q<CR> I feel like there is, or should be, a quicker way of doing this, though. What am I missing?

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  • Multiple Actions (Forms) on one Page - How not to lose master data, after editing detail data?

    - by nWorx
    Hello all, I've got a form where users can edit members of a group. So they have the possibilty to add members or remove existing members. So the Url goes like ".../Group/Edit/4" Where 4 is the id of the group. the view looks like this <% using (Html.BeginForm("AddUser", "Group")) %> <%{%> <label for="newUser">User</label> <%=Html.TextBox("username")%> <input type="submit" value="Add"/> </div> <%}%> <% using (Html.BeginForm("RemoveUser", "Group")) %> <%{%> <div class="inputItem"> <label for="groupMember">Bestehende Mitglieder</label> <%= Html.ListBox("groupMember", from g in Model.GetMembers() select new SelectListItem(){Text = g}) %> <input type="submit" value="Remove" /> </div> <%}%> The problem is that after adding or removing one user i lose the id of the group. What is the best solution for solving this kind of problem? Should I use hidden fields to save the group id? Thanks in advance.

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  • How do i write tasks? (parallel code)

    - by acidzombie24
    I am impressed with intel thread building blocks. I like how i should write task and not thread code and i like how it works under the hood with my limited understanding (task are in a pool, there wont be 100 threads on 4cores, a task is not guaranteed to run because it isnt on its own thread and may be far into the pool. But it may be run with another related task so you cant do bad things like typical thread unsafe code). I wanted to know more about writing task. I like the 'Task-based Multithreading - How to Program for 100 cores' video here http://www.gdcvault.com/sponsor.php?sponsor_id=1 (currently second last link. WARNING it isnt 'great'). My fav part was 'solving the maze is better done in parallel' which is around the 48min mark (you can click the link on the left side. That part is really all you need to watch if any). However i like to see more code examples and some API of how to write task. Does anyone have a good resource? I have no idea how a class or pieces of code may look after pushing it onto a pool or how weird code may look when you need to make a copy of everything and how much of everything is pushed onto a pool.

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  • Natural problems to solve using closures

    - by m.u.sheikh
    I have read quite a few articles on closures, and, embarassingly enough, I still don't understand this concept! Articles explain how to create a closure with a few examples, but I don't see any point in paying much attention to them, as they largely look contrived examples. I am not saying all of them are contrived, just that the ones I found looked contrived, and I dint see how even after understanding them, I will be able to use them. So in order to understand closures, I am looking at a few real problems, that can be solved very naturally using closures. For instance, a natural way to explain recursion to a person could be to explain the computation of n!. It is very natural to understand a problem like computing the factorial of a number using recursion. Similarly, it is almost a no-brainer to find an element in an unsorted array by reading each element, and comparing with the number in question. Also, at a different level, doing Object-oriented programming also makes sense. So I am trying to find a number of problems that could be solved with or without closures, but using closures makes thinking about them and solving them easier. Also, there are two types to closures, where each call to a closure can create a copy of the environment variables, or reference the same variables. So what sort of problems can be solved more naturally in which of the closure implementations?

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  • I am not able to update form data to MySQL using PHP and jQuery

    - by Jimson Jose
    My problem is that I am unable to update the values entered in the form. I have attached all the files. I'm using MYSQL database to fetch data. What happens is that I'm able to add and delete records from form using jQuery and PHP scripts to MYSQL database, but I am not able to update data which was retrieved from the database. The file structure is as follows: index.php is a file with jQuery functions where it displays form for adding new data to MYSQL using save.php file and list of all records are view without refreshing page (calling load-list.php to view all records from index.php works fine, and save.php to save data from form) - Delete is an function called from index.php to delete record from MySQL database (function calling delete.php works fine) - Update is an function called from index.php to update data using update-form.php by retriving specific record from MySQL table, (works fine) Problem lies in updating data from update-form.php to update.php (in which update query is written for MySQL) I have tried in many ways - at last I had figured out that data is not being transferred from update-form.php to update.php; there is a small problem in jQuery AJAX function where it is not transferring data to update.php page. Something is missing in calling update.php page it is not entering into that page. I am new bee in programming. I had collected this script from many forums and made this one. So I was limited in solving this problem. I came to know that this is good platform for me and many where we get a help to create new things. Please find the link below to download all files which is of 35kb (virus free assurance): download mysmallform files in ZIPped format, including mysql query

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  • Protecting Content with AuthLogic

    - by Rob Wilkerson
    I know this sounds like a really, really simple use case and I'm hoping that it is, but I swear I've looked all over the place and haven't found any mention of any way - not even the best way - of doing this. I'm brand-spanking new to Ruby, Rails and everything surrounding either (which may explain a lot). The dummy app that I'm using as my learning tool requires authentication in order to do almost anything meaningful, so I chose to start by solving that problem. I've installed the AuthLogic gem and have it working nicely to the extent that is covered by the intro documentation and Railscast, but now that I can register, login and logout...I need to do something with it. As an example, I need to create a page where users can upload images. I'm planning to have an ImagesController with an upload action method, but I want that only accessible to logged in users. I suppose that in every restricted action I could add code to redirect if there's no current_user, but that seems really verbose. Is there a better way of doing this that allows me to define or identify restricted areas and handle the authentication check in one place?

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  • Handling user interface in a multi-threaded application (or being forced to have a UI-only main thre

    - by Patrick
    In my application, I have a 'logging' window, which shows all the logging, warnings, errors of the application. Last year my application was still single-threaded so this worked [quite] good. Now I am introducing multithreading. I quickly noticed that it's not a good idea to update the logging window from different threads. Reading some articles on keeping the UI in the main thread, I made a communication buffer, in which the other threads are adding their logging messages, and from which the main thread takes the messages and shows them in the logging window (this is done in the message loop). Now, in a part of my application, the memory usage increases dramatically, because the separate threads are generating lots of logging messages, and the main thread cannot empty the communication buffer quickly enough. After the while the memory decreases again (if the other threads have finished their work and the main thread gradually empties the communication buffer). I solved this problem by having a maximum size on the communication buffer, but then I run into a problem in the following situation: the main thread has to perform a complex action the main thread takes some parts of the action and let's separate threads execute this while the seperate threads are executing their logic, the main thread processes the results from the other threads and continues with its work if the other threads are finished Problem is that in this situation, if the other threads perform logging, there is no UI-message loop, and so the communication buffer is filled, but not emptied. I see two solutions in solving this problem: require the main thread to do regular polling of the communication buffer only performing user interface logic in the main thread (no other logic) I think the second solution seems the best, but this may not that easy to introduce in a big application (in my case it performs mathematical simulations). Are there any other solutions or tips? Or is one of the two proposed the best, easiest, most-pragmatic solution? Thanks, Patrick

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  • Remove the Parent tag in xml using php

    - by Wasim
    I am facing a problem in editing a xml file. <?xml version="1.0" encoding="UTF-8"?> <urlset> <url> <loc>http://www.abc.com/</loc> <lastmod>2010-04-17T17:23:57+00:00</lastmod> <changefreq>daily</changefreq> <priority>0.50</priority> </url> <url> <loc>http://www.abc.com/</loc> <lastmod>2010-04-17T17:23:57+00:00</lastmod> <changefreq>daily</changefreq> <priority>0.50</priority> </url> </urlset> I want to add one more set of records starting with <url> with its other tags, (i.e) "loc,lastmod,changefreq,priority" and than save the xml file.For adding the new record i need to remove the parent closing tag that is </urlset> and than add the rest of the records and close the main tag. Can anyone please help me solving my problem.Thanks

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  • What should be taught in a "Fundamentals of programming" course at university?

    - by Dervin Thunk
    I have started a new question (see here), because I think the topic is of importance in a more general form. The question is now: If you were a professor at a Computer Science Dept. in some university, what would make it into your course? This is a programming course, second term, first year computer science/computer engineering. Remember you have a limited amount of time, and students are of different levels of competence, and some may be scientists, but some will also go on to be programmers in companies of different kinds. You have to cater to all. Bonus: What language? (Although see this question for my current thoughts about this...) Maybe you want to attach a course outline from some university? See here for an even more general question about this. Answer: I can't really summarize this post... I guess it was too subjective. However, it looks like we have to cover the history of computing up to a certain extent, computer architecture (memory, registers, whatever), C, and finally some basic algos and data structures in a problem solving fashion. This will be the bare bones of the course. Thanks all. I will accept the most voted up answer to close the thread, as it should be done.

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  • Simple encryption - Sum of Hashes in C

    - by Dogbert
    I am attempting to demonstrate a simple proof of concept with respect to a vulnerability in a piece of code in a game written in C. Let's say that we want to validate a character login. The login is handled by the user choosing n items, (let's just assume n=5 for now) from a graphical menu. The items are all medieval themed: eg: _______________________________ | | | | | Bow | Sword | Staff | |-----------|-----------|-------| | Shield | Potion | Gold | |___________|___________|_______| The user must click on each item, then choose a number for each item. The validation algorithm then does the following: Determines which items were selected Drops each string to lowercase (ie: Bow becomes bow, etc) Calculates a simple string hash for each string (ie: `bow = b=2, o=15, w=23, sum = (2+15+23=40) Multiplies the hash by the value the user selected for the corresponding item; This new value is called the key Sums together the keys for each of the selected items; this is the final validation hash IMPORTANT: The validator will accept this hash, along with non-zero multiples of it (ie: if the final hash equals 1111, then 2222, 3333, 8888, etc are also valid). So, for example, let's say I select: Bow (1) Sword (2) Staff (10) Shield (1) Potion (6) The algorithm drops each of these strings to lowercase, calculates their string hashes, multiplies that hash by the number selected for each string, then sums these keys together. eg: Final_Validation_Hash = 1*HASH(Bow) + 2*HASH(Sword) + 10*HASH(Staff) + 1*HASH(Shield) + 6*HASH(Potion) By application of Euler's Method, I plan to demonstrate that these hashes are not unique, and want to devise a simple application to prove it. in my case, for 5 items, I would essentially be trying to calculate: (B)(y) = (A_1)(x_1) + (A_2)(x_2) + (A_3)(x_3) + (A_4)(x_4) + (A_5)(x_5) Where: B is arbitrary A_j are the selected coefficients/values for each string/category x_j are the hash values for each string/category y is the final validation hash (eg: 1111 above) B,y,A_j,x_j are all discrete-valued, positive, and non-zero (ie: natural numbers) Can someone either assist me in solving this problem or point me to a similar example (ie: code, worked out equations, etc)? I just need to solve the final step (ie: (B)(Y) = ...). Thank you all in advance.

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  • OpenGLES - Rendering a background image only once and not wiping it

    - by chaosbeaker
    Hello, first time asking a question here but been watching others answers for a while. My own question is one for improving the performance of my program. Currently I'm wiping the viewFrameBuffer on each pass through my program and then rendering the background image first followed by the rest of my scene. I was wondering how I go about rendering the background image once, and only wiping the rest of the scene for updating/re-rendering. I tried using a seperate buffer but I'm not sure how to present this new buffer to the render buffer. // Set the current EAGLContext and bind to the framebuffer. This will direct all OGL commands to the // framebuffer and the associated renderbuffer attachment which is where our scene will be rendered [EAGLContext setCurrentContext:context]; glBindFramebufferOES(GL_FRAMEBUFFER_OES, viewFramebuffer); // Define the viewport. Changing the settings for the viewport can allow you to scale the viewport // as well as the dimensions etc and so I'm setting it for each frame in case we want to change i glViewport(0, 0, screenBounds.size.width , screenBounds.size.height); // Clear the screen. If we are going to draw a background image then this clear is not necessary // as drawing the background image will destroy the previous image glClearColor(0.0f, 1.0f, 0.0f, 1.0f); glClear(GL_COLOR_BUFFER_BIT); // Setup how the images are to be blended when rendered. This could be changed at different points during your // render process if you wanted to apply different effects glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA); switch (currentViewInt) { case 1: { [background render:CGPointMake(240, 0) fromTopLeftBottomRightCenter:@"Bottom"]; // Other Rendering Code }} // Bind to the renderbuffer and then present this image to the current context glBindRenderbufferOES(GL_RENDERBUFFER_OES, viewRenderbuffer); [context presentRenderbuffer:GL_RENDERBUFFER_OES]; Hopefully by solving this I'll also be able to implement another buffer just for rendering particles as I can set them to always use a black background as their alpha source. Any help is greatly appreciated

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  • How do i write task? (parallel code)

    - by acidzombie24
    I am impressed with intel thread building blocks. I like how i should write task and not thread code and i like how it works under the hood with my limited understanding (task are in a pool, there wont be 100 threads on 4cores, a task is not guaranteed to run because it isnt on its own thread and may be far into the pool. But it may be run with another related task so you cant do bad things like typical thread unsafe code). I wanted to know more about writing task. I like the 'Task-based Multithreading - How to Program for 100 cores' video here http://www.gdcvault.com/sponsor.php?sponsor_id=1 (currently second last link. WARNING it isnt 'great'). My fav part was 'solving the maze is better done in parallel' which is around the 48min mark (you can click the link on the left side). However i like to see more code examples and some API of how to write task. Does anyone have a good resource? I have no idea how a class or pieces of code may look after pushing it onto a pool or how weird code may look when you need to make a copy of everything and how much of everything is pushed onto a pool.

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  • Determining polygon intersection and containment

    - by Victor Liu
    I have a set of simple (no holes, no self-intersections) polygons, and I need to check that they don't intersect each other (one can be entirely contained in another; that is okay). I can check this by simply checking the per-vertex inside-ness of one polygon versus other polygons. I also need to determine the containment tree, which is the set of relationships that say which polygon contains any given polygon. Since no polygon can intersect any other, then any contained polygon has a unique container; the "next-bigger" one. In other words, if A contains B contains C, then A is the parent of B, and B is the parent of C, and we don't consider A the parent of C. The question: How do I efficiently determine the containment relationships and check the non-intersection criterion? I ask this as one question because maybe a combined algorithm is more efficient than solving each problem separately. The algorithm should take as input a list of polygons, given by a list of their vertices. It should produce a boolean B indicating if none of the polygons intersect any other polygon, and also if B = true, a list of pairs (P, C) where polygon P is the parent of child C. This is not homework. This is for a hobby project I am working on.

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  • Going "behind Hibernate's back" to update foreign key values without an associated entity

    - by Alex Cruise
    Updated: I wound up "solving" the problem by doing the opposite! I now have the entity reference field set as read-only (insertable=false updatable=false), and the foreign key field read-write. This means I need to take special care when saving new entities, but on querying, the entity properties get resolved for me. I have a bidirectional one-to-many association in my domain model, where I'm using JPA annotations and Hibernate as the persistence provider. It's pretty much your bog-standard parent/child configuration, with one difference being that I want to expose the parent's foreign key as a separate property of the child alongside the reference to a parent instance, like so: @Entity public class Child { @Id @GeneratedValue Long id; @Column(name="parent_id", insertable=false, updatable=false) private Long parentId; @ManyToOne(cascade=CascadeType.ALL) @JoinColumn(name="parent_id") private Parent parent; private long timestamp; } @Entity public class Parent { @Id @GeneratedValue Long id; @OrderBy("timestamp") @OneToMany(mappedBy="parent", cascade=CascadeType.ALL, fetch=FetchType.LAZY) private List<Child> children; } This works just fine most of the time, but there are many (legacy) cases when I'd like to put an invalid value in the parent_id column without having to create a bogus Parent first. Unfortunately, Hibernate won't save values assigned to the parentId field due to insertable=false, updatable=false, which it requires when the same column is mapped to multiple properties. Is there any nice way to "go behind Hibernate's back" and sneak values into that field without having to drop down to JDBC or implement an interceptor? Thanks!

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  • protocol parsing in c

    - by nomad.alien
    I have been playing around with trying to implement some protocol decoders, but each time I run into a "simple" problem and I feel the way I am solving the problem is not optimal and there must be a better way to do things. I'm using C. Currently I'm using some canned data and reading it in as a file, but later on it would be via TCP or UDP. Here's the problem. I'm currently playing with a binary protocol at work. All fields are 8 bits long. The first field(8bits) is the packet type. So I read in the first 8 bits and using a switch/case I call a function to read in the rest of the packet as I then know the size/structure of it. BUT...some of these packets have nested packets inside them, so when I encounter that specific packet I then have to read another 8-16 bytes have another switch/case to see what the next packet type is and on and on. (Luckily the packets are only nested 2 or 3 deep). Only once I have the whole packet decoded can I handle it over to my state machine for processing. I guess this can be a more general question as well. How much data do you have to read at a time from the socket? As much as possible? As much as what is "similar" in the protocol headers? So even though this protocol is fairly basic, my code is a whole bunch of switch/case statements and I do a lot of reading from the file/socket which I feel is not optimal. My main aim is to make this decoder as fast as possible. To the more experienced people out there, is this the way to go or is there a better way which I just haven't figured out yet? Any elegant solution to this problem?

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  • Uva's 3n+1 problem

    - by dmindreader
    I'm solving Uva's 3n+1 problem and I don't get why the judge is rejecting my answer. The time limit hasn't been exceeded and the all test cases I've tried have run correctly so far. import java.io.*; public class NewClass{ /** * @param args the command line arguments */ public static void main(String[] args) throws IOException { int maxCounter= 0; int input; int lowerBound; int upperBound; int counter; int numberOfCycles; int maxCycles= 0; int lowerInt; BufferedReader consoleInput = new BufferedReader(new InputStreamReader(System.in)); String line = consoleInput.readLine(); String [] splitted = line.split(" "); lowerBound = Integer.parseInt(splitted[0]); upperBound = Integer.parseInt(splitted[1]); int [] recentlyused = new int[1000001]; if (lowerBound > upperBound ) { int h = upperBound; upperBound = lowerBound; lowerBound = h; } lowerInt = lowerBound; while (lowerBound <= upperBound) { counter = lowerBound; numberOfCycles = 0; if (recentlyused[counter] == 0) { while ( counter != 1 ) { if (recentlyused[counter] != 0) { numberOfCycles = recentlyused[counter] + numberOfCycles; counter = 1; } else { if (counter % 2 == 0) { counter = counter /2; } else { counter = 3*counter + 1; } numberOfCycles++; } } } else { numberOfCycles = recentlyused[counter] + numberOfCycles; counter = 1; } recentlyused[lowerBound] = numberOfCycles; if (numberOfCycles > maxCycles) { maxCycles = numberOfCycles; } lowerBound++; } System.out.println(lowerInt +" "+ upperBound+ " "+ (maxCycles+1)); } }

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  • What do you mean by the expressiveness in programming lanuguage?

    - by prosseek
    I see a lot of the word 'expressiveness' when people want to stress one language is better than the other. But I don't see exactly what they mean by it. Is it the verboseness/succinctness? I mean, if one language can write down something shorter than the other, does that mean expressiveness? Please refer to my other question - http://stackoverflow.com/questions/2411772/article-about-code-density-as-a-measure-of-programming-language-power Is it the power of the language? Paul Graham says that one language is more powerful than the other language in a sense that one language can do that the other language can't do (for example, LISP can do something with macro that the other language can't do). Is it just something that makes life easier? Regular expression can be one of the examples. Is it a different way of solving the same problem: something like SQL to solve the search problem? What do you think about the expressiveness of a programming lanuage? Can you show the expressiveness using some code? What's the relationship with the expressiveness and DSL? Do people come up with DSL to get the expressiveness?

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  • Client-server synchronization pattern / algorithm?

    - by tm_lv
    I have a feeling that there must be client-server synchronization patterns out there. But i totally failed to google up one. Situation is quite simple - server is the central node, that multiple clients connect to and manipulate same data. Data can be split in atoms, in case of conflict, whatever is on server, has priority (to avoid getting user into conflict solving). Partial synchronization is preferred due to potentially large amounts of data. Are there any patterns / good practices for such situation, or if you don't know of any - what would be your approach? Below is how i now think to solve it: Parallel to data, a modification journal will be held, having all transactions timestamped. When client connects, it receives all changes since last check, in consolidated form (server goes through lists and removes additions that are followed by deletions, merges updates for each atom, etc.). Et voila, we are up to date. Alternative would be keeping modification date for each record, and instead of performing data deletes, just mark them as deleted. Any thoughts?

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