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  • Is there a difference here?

    - by HotHead
    Please consider following code: 1. uint16 a = 0x0001; if(a < 0x0002) { // do something } 2. uint16 a = 0x0001; if(a < uint16(0x0002)) { // do something } 3. uint16 a = 0x0001; if(a < static_cast<uint16>(0x0002)) { // do something } 4. uint16 a = 0x0001; uint16 b = 0x0002; if(a < b) { // do something } What compiler does in backgorund and what is the best (and correct) way to do above testing? p.s. sorry, but I couldn't find the better title :) Thank you in advance!

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  • Recursive function causing a stack overflow

    - by dbyrne
    I am trying to write a simple sieve function to calculate prime numbers in clojure. I've seen this question about writing an efficient sieve function, but I am not to that point yet. Right now I am just trying to write a very simple (and slow) sieve. Here is what I have come up with: (defn sieve [potentials primes] (if-let [p (first potentials)] (recur (filter #(not= (mod % p) 0) potentials) (conj primes p)) primes)) For small ranges it works fine, but causes a stack overflow for large ranges: user=> (sieve (range 2 30) []) [2 3 5 7 11 13 17 19 23 29] user=> (sieve (range 2 15000) []) java.lang.StackOverflowError (NO_SOURCE_FILE:0) I thought that by using recur this would be a non-stack-consuming looping construct? What am I missing?

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  • How to share a variable between two classes?

    - by Altefquatre
    How would you share the same object between two other objects? For instance, I'd like something in that flavor: class A { private string foo_; // It could be any other class/struct too (Vector3, Matrix...) public A (string shared) { this.foo_ = shared; } public void Bar() { this.foo_ = "changed"; } } ... // inside main string str = "test"; A a = new A(str); Console.WriteLine(str); // "test" a.Bar(); Console.WriteLine(str); // I get "test" instead of "changed"... :( I read there is some ref/out stuff, but I couldn't get what I'm asking here. I could only apply some changes in the methods scope where I was using ref/out arguments... I also read we could use pointers, but is there no other way to do it?

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  • Problems with rails and saving to the database.

    - by Grantismo
    I've been having some difficulty in understanding the source of a problem. Below is a listing of the model classes. Essentially the goal is to have the ability to add sentences to the end of the story, or to add stories to an existing sentence_block. Right now, I'm only attempting to allow users to add sentences, and automatically create a new sentence_block for the new sentence. class Story < ActiveRecord::Base has_many :sentence_blocks, :dependent => :destroy has_many :sentences, :through => :sentence_blocks accepts_nested_attributes_for :sentence_blocks end class SentenceBlock < ActiveRecord::Base belongs_to :story has_many :sentences, :dependent => :destroy end class Sentence < ActiveRecord::Base belongs_to :sentence_block def story @sentence_block = SentenceBlock.find(self.sentence_block_id) Story.find(@sentence_block.story_id) end end The problem is occurring when using the show method of the Story. The Story method is as follows, and the associated show method for a sentence is also included. Sentence.show def show @sentence = Sentence.find(params[:id]) respond_to do |format| format.html {redirect_to(@sentence.story)} format.xml { render :xml => @sentence } end end Story.show def show @story = Story.find(params[:id]) @sentence_block = @story.sentence_blocks.build @new_sentence = @sentence_block.sentences.build(params[:sentence]) respond_to do |format| if @new_sentence.content != nil and @new_sentence.sentence_block_id != nil and @sentence_block.save and @new_sentence.save flash[:notice] = 'Sentence was successfully added.' format.html # new.html.erb format.xml { render :xml => @story } else @sentence_block.destroy format.html format.xml { render :xml => @story } end end end I'm getting a "couldn't find Sentence_block without and id" error. So I'm assuming that for some reason the sentence_block isn't getting saved to the database. Can anyone help me with my understanding of the behavior and why I'm getting the error? I'm trying to ensure that every time the view depicts show for a story, an unnecessary sentence_block and sentence isn't created, unless someone submits the form, I'm not really sure how to accomplish this. Any help would be appreciated.

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  • How to deal with clients and iterations in Agile team?

    - by Ondrej Slinták
    This thread is a follow up to my previous one. It's in fact 2 questions, so I hope no one minds, as they are dependent on each other. We are starting a new project at work and we consider it as a great opportunity to try Agile techniques in action. We had a brainstorming about ideas we read in several books and articles, and came up with concept that would suit us the best: 2 weeks iteration, followed by call with clients who would choose what stuff they want to have in next iteration. I just have few more questions, which we couldn't figure out ourselves. What to do in the first iteration? What to, generally, do in the first few iterations if we start from the scratch? Just give it a month of development to code core of the application or start with simple wire-frames with limited pre-coded functionality? What usually clients want to see? Shiny stuff that doesn't work or ugly stuff that does work? How to communicate with clients? Our initial thought it to set the process to something like this: Is it a good idea to have a Focal Point on client side or is it better to communicate straight with all the clients to prevent miscommunication? Any thoughts are welcome! Thanks in advance.

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  • Using GA in GUI

    - by AlexT
    Sorry if this isn't clear as I'm writing this on a mobile device and I'm trying to make it quick. I've written a basic Genetic Algorithm with a binary encoding (genes) that builds a fitness value and evolves through several iterations using tournament selection, mutation and crossover. As a basic command-line example it seems to work. The problem I've got is with applying a genetic algorithm within a GUI as I am writing a maze-solving program that uses the GA to find a method through a maze. How do I turn my random binary encoded genes and fitness function (add all the binary values together) into a method to control a bot around a maze? I have built a basic GUI in Java consisting of a maze of labels (like a grid) with the available routes being in blue and the walls being in black. To reiterate my GA performs well and contains what any typical GA would (fitness method, get and set population, selection, crossover, etc) but now I need to plug it into a GUI to get my maze running. What needs to go where in order to get a bot that can move in different directions depending on what the GA says? Rough pseudocode would be great if possible As requested, an Individual is built using a separate class (Indiv), with all the main work being done in a Pop class. When a new individual is instantiated an array of ints represent the genes of said individual, with the genes being picked at random from a number between 0 and 1. The fitness function merely adds together the value of these genes and in the Pop class handles selection, mutation and crossover of two selected individuals. There's not much else to it, the command line program just shows evolution over n generations with the total fitness improving over each iteration. EDIT: It's starting to make a bit more sense now, although there are a few things that are bugging me... As Adamski has suggested I want to create an "Agent" with the options shown below. The problem I have is where the random bit string comes into play here. The agent knows where the walls are and has it laid out in a 4 bit string (i.e. 0111), but how does this affect the random 32 bit string? (i.e. 10001011011001001010011011010101) If I have the following maze (x is the start place, 2 is the goal, 1 is the wall): x 1 1 1 1 0 0 1 0 0 1 0 0 0 2 If I turn left I'm facing the wrong way and the agent will move completely off the maze if it moves forward. I assume that the first generation of the string will be completely random and it will evolve as the fitness grows but I don't get how the string will work within a maze. So, to get this straight... The fitness is the result of when the agent is able to move and is by a wall. The genes are a string of 32 bits, split into 16 sets of 2 bits to show the available actions and for the robot to move the two bits need to be passed with four bits from the agent showings its position near the walls. If the move is to go past a wall the move isn't made and it is deemed invalid and if the move is made and if a new wall is found then the fitness goes up. Is that right?

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  • Is using the break statement bad practice?

    - by Lchi
    I've been told by professors and peers at my university that using the break statement is bad practice, but through my coursework haven't come up with a great reason why. Those who claim that it is bad say that it's a "get out of jail free card" and that you can always avoid using it. My guesses for why its considered bad would be that you could possibly skip some cleanup code after the break, or similarly exit some control structure in an inconsistent state. Is there any reason why using break is(n't) bad practice?

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  • Should I add try/catch around when casting on an attribute of JSP implicit object?

    - by Michael Mao
    Hi all: Basically what I mean is like this: List<String[]> routes = (List<String[]>)application.getAttribute("routes"); For the above code, it tries to get an attribute named "routes" from the JSP implicit object - application. But as everyone knows, after this line of code, routes may very well contains a null - which means this application hasn't got an attribute named "routes". Is this "casting on null" good programming practice in Java or not? Basically I try to avoid exceptions such as java.io.InvalidCastException I reckon things like this are more as "heritage" of Java 1.4 when generic types were not introduced to this language. So I guess everything stored in application attributes as Objects (Similar to traditional ArrayList). And when you do "downcast", there might be invalid casts. What would you do in this case? Update: Just found that although in the implicit object application I did store a List of String arrays, when I do this : List<double[]> routes = (List<double[]>)application.getAttribute("routes"); It doesn't produce any error... And I felt not comfortable already... And even with this code: out.print(routes.get(0)); It does print out something strange : [Ljava.lang.String;@18b352f Am I printing a "pointer to String"? I can finally get an exception like this: out.print(routes.get(0)[1]); with error : java.lang.ClassCastException: [Ljava.lang.String; Because it was me to add the application attribute, I know which type should it be cast to. I feel this is not "good enough", what if I forget the exact type? I know there are still some cases where this sort of thing would happen, such as in JSP/Servlet when you do casting on session attributes. Is there a better way to do this? Before you say:"OMG, why you don't use Servlets???", I should justify my reason as this: - because my uni sucks, its server can only work with Servlets generated by JSP, and I don't really want to learn how to fix issues like that. look at my previous question on this , and this is uni homework, so I've got no other choice, forget all about war, WEB-INF,etc, but "code everything directly into JSP" - because the professors do that too. :)

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  • My Ruby Code: How can I improve? (Java to Ruby guy)

    - by steve
    Greetings, I get the feeling that I'm using ruby in an ugly way and possibly missing out on tonnes of useful features. I was wondering if anyone could point out a cleaner better way to write my code which is pasted here. The code itself simply scrapes some data from yelp and processes it into a json format. The reason I'm not using hash.to_json is because it throws some sort of stack error which I can only assume is due to the hash being too large (It's not particularly large). Response object = a hash text = the output which saves to file Anyways guidance appreciated. def mineLocation client = Yelp::Client.new request = Yelp::Review::Request::GeoPoint.new(:latitude=>13.3125,:longitude => -6.2468,:yws_id => 'nicetry') response = client.search(request) response['businesses'].length.times do |businessEntry| text ="" response['businesses'][businessEntry].each { |key, value| if value.class == Array value.length.times { |arrayEntry| text+= "\"#{key}\":[" value[arrayEntry].each { |arrayKey,arrayValue| text+= "{\"#{arrayKey}\":\"#{arrayValue}\"}," } text+="]" } else text+="\"#{arrayKey}\":\"#{arrayValue}\"," end } end end

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  • Tutorial/resource for implementing VM

    - by zaharpopov
    Hello, I want self-education purpose implement a simple virtual machine for a dynamic language, prefer in C language. Something like the Lua VM, or Parrot, or Python VM, but simpler. Are there any good resources/tutorials on achieving this, apart from looking at code and design documentations of the existing VMs? Thanks in advance for your answers and ideas Edit: why close vote? I don't understand - is this not programming. Please comment if there is specific problem with my question.

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  • Global and local variables in my script

    - by Acorn
    I'm starting out learning javascript, and tried to write a little script that would make a grid of divs on a page. Here's the script: var tileWidth=50; var tileHeight=100; var leftPos=10; var topPos=10; var columns=10; var rows=10; var spacing=5; $('document').ready(function() { placeTiles(); }); function makeRow() { for (var i=0; i<columns; i++) { $('#canvas').append('<div class="tile" style="left:' + leftPos + 'px;top:' + topPos + 'px;"></div>'); var leftPos = leftPos + tileWidth + spacing; } } function placeTiles() { for (var i=0; i<rows; i++) { makeRow(); var topPos = topPos + tileHeight + spacing; } } At the moment, 100 <div>s get created, all with a top position of 10px and a left position of undefined (for the first <div> in the row) or NaN. What should I be doing differently? Why can't makerow() see my global leftPos variable (and all the other variables for that matter)? Thanks.

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  • Loading attribute in XPATH, problem

    - by Nguyen Quoc Hung
    I've got a question about loading attribute in XPATH. I write short XML code to test: <?xml version="1.0" encoding="iso-8859-1"?> <?xml-stylesheet type="text/xsl" href="testDate.xsl"?> <element attribute="1/1/2100"> Hung </element> My XSL code: <?xml version="1.0" encoding="iso-8859-1"?> <xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"> <!--Handle the document: set up HTML page--> <xsl:template match="/"> <html> <head> </head> <body> This is a test <xsl:value-of select="element@attribute"/> </body> </html> </xsl:template> </xsl:stylesheet> Why it produces an error when loading the stylesheet? Would you please help me explain this? Thank you

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  • LaTex: how does the include-command work?

    - by HH
    I supposed the include-command copy-pastes code in the compilation, it is wrong because the code stopped working. Please, see the middle part in the code. I only copy-pasted the code to the file and added the include-command. $ cat results/frames.tex 10.31 & 8.50 & 7.40 \\ 10.34 & 8.53 & 7.81 \\ 8.22 & 8.62 & 7.78 \\ 10.16 & 8.53 & 7.44 \\ 10.41 & 8.38 & 7.63 \\ 10.38 & 8.57 & 8.03 \\ 10.13 & 8.66 & 7.41 \\ 8.50 & 8.60 & 7.15 \\ 10.41 & 8.63 & 7.21 \\ 8.53 & 8.53 & 7.12 \\ Latex code \begin{table} \begin{tabular}{ | l | m | r |} \hline $t$ / s & $d_{1}$ / s & $d_{2}$ / s \\ $\Delta h = 0,01 s$ & $\Delta d = 0,01 s$ & $\Delta d = 0,01 s$ \\ \hline % I JUST COPIED THE CODE from here to the file, included. % It stopped working, why? \include{results/frames.tex} \hline $\pi (\frac{d_{1}}{2} - \frac{d_{2}}{2})$ & $2 \pi R h$ & $2 \pi r h$ \\ \hline \end{tabular} \end{table}

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  • QT4 Designer - Implement Widget

    - by MOnsDaR
    I'm currently trying to get into QT4 and figure out a workflow for myself. While trying to create a widget which allows the user to connect to a hostname:port some questions appeared. The widget itself contains a LineEdit for entering the hostname, a SpinBox for entering the port and a PushButton which should emit a connect(QString hostname, unsigned int port) signal. In QTDesigner I created the necessary Form. It is saved as a .ui-File. Now the big question is how could I implement the widget? Is there a place in QTDesigner where I could add my signal to the Widget? Where could I add custom Properties? I've learned in another tutorial, which showed how to create a Widget in C++, how signals, slots, Q_PROPERTIES etc are defined and added to the widget. But there is no sourcecode in QTDesigner. Another option would be to generate sourcecode using uic. But the header says, that another generate would overwrite any changes to the sourcefiles. So how can I create a QT-widget completely with my own signals, slots and properties by using the QTDesigner for creating the UI and not having to recode everything whenever the UI is changing. Is there some kind of Roundtrip-Engineering? If thats not possible: Whats the sense of creating a Widget with QTDesigner then?

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  • How to make a php function contain mysql commands

    - by bob
    I want to create a simple menu function which can call it example get_menu() Here is my current code. <?php $select = 'SELECT * FROM pages'; $query = $db->rq($select); while ($page = $db->fetch($query)) { $id = $page['id']; $title = $page['title']; ?> <a href="page.php?id<?php echo $id; ?>" title="<?php echo $title; ?>"><?php echo $title; ?></a> <?php } ?> How to do that in? function get_menu() { } Let me know.

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  • C# Proxy, what is the best way to do this?

    - by Kin
    I'm writing a proxy using .NET and C#. It has a couple of functions that it needs to fulfill. I haven't done much Socket programming, and I am not sure the best way to go about it. Should I use Synchronous Sockets, Asynchronous sockets? Please help! It must... Accept Connections from the client on two different ports, and be able to receive data on both ports at the same time. When a connection is made on a port, it must immediately connect to the server, and start sending data as it receives it from the client to the server. Packets must be forwarded in the order they are received, exactly as they were received. It needs to be as low latency as possible. I don't need the ability for multiple clients to use the proxy, but it would be a nice feature if its easy to implement.

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  • Calling button in Action Script 3.0

    - by Meko
    I am trying to make button panel. each button have two type btn_home and btn_home_white I am trying to reach those buttons.It is work if I write for each button their own methods like btn_home.addEventListener(MouseEvent.MOUSE_OVER,overEffect); btn_home_white.addEventListener(MouseEvent.MOUSE_OUT,outEffect); function overEffect(e:MouseEvent) { var myTweenHight:Tween = new Tween( btn_home,"height",Bounce.easeOut,25,0,3,true); var myTweenHight2:Tween = new Tween(btn_home_white,"height",Bounce.easeOut,0,25,3,true); var myTweenAlpha:Tween = new Tween(btn_home_white,"alpha",Strong.easeOut,0,1,2,true); } function outEffect(e:MouseEvent) { var myTweenHight:Tween = new Tween btn_home,"height",Bounce.easeOut,0,25,3,true); var myTweenHight2:Tween = new Tween(btn_home_white,"height",Bounce.easeOut,25,0,3,true); var myTweenAlpha:Tween = new Tween(btn_home_white,"alpha",Strong.easeOut,1,0,2,true); } But I have 10 buttons as btn_buttonname and btn_buttonname_white . I tryed to create Event listener on stage for all.It works for firts type buttons btn_buttonname but How can I get second type buttons? I tryed e.target["_white"] but it does not work . stage.addEventListener(MouseEvent.MOUSE_OVER , overEffect); stage.addEventListener(MouseEvent.MOUSE_OUT , outEffect); function overEffect(e:MouseEvent) { var myTweenHight:Tween = new Tween(e.target,"height",Bounce.easeOut,25,0,3,true); trace("height"); var myTweenHight2:Tween = new Tween(e.target["_white"],"height",Bounce.easeOut,0,25,3,true); var myTweenAlpha:Tween = new Tween(e.target["_white"],"alpha",Strong.easeOut,0,1,2,true); } function outEffect(e:MouseEvent) { var myTweenHight:Tween = new Tween(e.target,"height",Bounce.easeOut,0,25,3,true); var myTweenHight2:Tween = new Tween(e.target["_white"],"height",Bounce.easeOut,25,0,3,true); var myTweenAlpha:Tween = new Tween(e.target["_white"],"alpha",Strong.easeOut,1,0,2,true); }

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  • magento - webserver question

    - by WANNABE
    I've uploaded the Magento installation file to my hosting and I've been told to go to the URL you uploaded it to using you browser, then the installation wizard will run you through the processes. I uploaded to /home/domain/public_html/magneto What URL should I use to access it? Thanks in advance

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  • XML and HTML = need help using HTML code

    - by whitstone86
    I'm converting my static HTML site to a dynamic PHP/XML-driven one. This is my current code: <div class="divider"></div> <div class="main" style="width: 552px;"> <div class="time">00:00</div> <div class="show"><h3><b>Radio Show</b></h3> <p>Description</p></div> <div class="footer"></div> </div> and my XML file: <?xml version="1.0"?> <show> <showdesc> <divider1></divider1> <divmain></divmain> <airtime></airtime> <presenter></presenter> <showinfo></showinfo> <divfooter></divfooter> </showdesc> which is the above HTML, that I'm trying to get into the XML file. I don't know how to get it to get the info in, I can display a simple XML page, as suggested here: http://www.kirupa.com/web/xml_php_parse_intermediate.htm but I am trying to in PHP get this to display what's in the XML pages or display this output: "Sorry. No schedule page is available" if the XML is blank, as above. Anyone able to help me fix this? I've tried and tried but it's baffling me... Thanks.

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