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  • declare decision structure inside of a System.out.println

    - by user2899249
    So I am working on an assignment where I have to have a print method in a constructor that displays a distance. I also have to have three separate get methods depending on what the input is in the demo class. My question is that I am trying to write the print method to contain a decision structure based on which get is used. public void prt() { DecimalFormat formatter = new DecimalFormat("#,##0.00"); System.out.println("The time it takes the sound to travel " + distance + " feet through air is " + if (getSpeedInAir() > 0) { formatter.format(getSpeedInAir()); } else if (getSpeedInWater() > 0) { formatter.format(getSpeedInWater()); } else if (getSpeedInSteel() > 0) { formatter.format(getSpeedInSteel()); } else "error";) } After trying to compile I am getting the following errors. Microsoft Windows [Version 6.1.7601] Copyright (c) 2009 Microsoft Corporation. All rights reserved. C:\Users\GlaDOS\Desktop\JavaStuffj Speed C:\Users\GlaDOS\Desktop\JavaStuffdel *.class C:\Users\GlaDOS\Desktop\JavaStuffjavac Speed.java Speed.java:43: error: illegal start of expression " feet through air is " + if (getSpeedInAir() 0) ^ Speed.java:43: error: ';' expected " feet through air is " + if (getSpeedInAir() 0) ^ Speed.java:43: error: not a statement " feet through air is " + if (getSpeedInAir() 0) ^ Speed.java:43: error: ';' expected " feet through air is " + if (getSpeedInAir() 0) ^ Speed.java:47: error: 'else' without 'if' else if (getSpeedInWater() > 0) ^ Speed.java:56: error: not a statement "error";) ^ Speed.java:56: error: illegal start of expression "error";) ^ 7 errors C:\Users\GlaDOS\Desktop\JavaStuffjava Speed Error: Could not find or load main class Speed Any help on why this is happening would be greatly appreciated.

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  • Java JCheckBox ArrayList help needed

    - by user2929626
    I'm new to Java and struggling with something which I'm sure must have a simple answer but I can't seem to find it. I have an array of checkbox objects defined as: ArrayList<JCheckBox> checkBoxList A JPanel is created with a grid layout and the checkboxes are added to the JPanel and the ArrayList: for (int i = 0; i < 256; i++) { JCheckBox c = new JCheckBox(); c.setSelected(false); checkBoxList.add(c); mainPanel.add(c); } Yes, there are 256 checkboxes! The panel is added to a JFrame and eventually the GUI is displayed. The user can select any combination of the 256 checkboxes. My class implements Serializable and this ArrayList of checkboxes can be saved and restored using 'Save' and 'Load' GUI buttons. My code to load the saved object is as below: public class LoadListener implements ActionListener { public void actionPerformed(ActionEvent a) { try { // Prompt the user for a load file JFileChooser fileLoad = new JFileChooser(); fileLoad.showOpenDialog(mainFrame); // Create a object/file input stream linking to the selected file ObjectInputStream is = new ObjectInputStream(new FileInputStream(fileLoad.getSelectedFile())); // Read the checkBox array list checkBoxList = (ArrayList<JCheckBox>) is.readObject(); is.close(); } catch (Exception ex) { ex.printStackTrace(); } } On loading the ArrayList object, the values of the checkboxes are correctly populated, however I want to update the checkboxes on the GUI to reflect this. Is there an easy way to do this? I assumed as the array of checkboxes had the correct values that I could just repaint the panel / frame but this doesn't work. I'd like to understand why - does my loaded array of checkbox objects no longer reflect the checkbox objects on the GUI? Any help would be much appreciated. Thanks!

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  • C++ STL question related to insert iterators and overloaded operators

    - by rshepherd
    #include <list> #include <set> #include <iterator> #include <algorithm> using namespace std; class MyContainer { public: string value; MyContainer& operator=(const string& s) { this->value = s; return *this; } }; int main() { list<string> strings; strings.push_back("0"); strings.push_back("1"); strings.push_back("2"); set<MyContainer> containers; copy(strings.begin(), strings.end(), inserter(containers, containers.end())); } The preceeding code does not compile. In standard C++ fashion the error output is verbose and difficult to understand. The key part seems to be this... /usr/include/c++/4.4/bits/stl_algobase.h:313: error: no match for ‘operator=’ in ‘__result.std::insert_iterator::operator* [with _Container = std::set, std::allocator ]() = __first.std::_List_iterator::operator* [with _Tp = std::basic_string, std::allocator ]()’ ...which I interpet to mean that the assignment operator needed is not defined. I took a look at the source code for insert_iterator and noted that it has overloaded the assignment operator. The copy algorithm must uses the insert iterators overloaded assignment operator to do its work(?). I guess that because my input iterator is on a container of strings and my output iterator is on a container of MyContainers that the overloaded insert_iterator assignment operator can no longer work. This is my best guess, but I am probably wrong. So, why exactly does this not work and how can I accomplish what I am trying to do?

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  • What do you call a generalized (non-GUI-related) "Model-View-Controller" architecture?

    - by dcuccia
    I am currently refactoring code that coordinates multiple hardware components for data acquisition, and feeling a bit like I'm recreating the wheel. In particular, an MVC-like pattern seems to be emerging. Except, this has nothing to do with a GUI and I'm worried that I'm forcing this particular pattern where another might be more appropriate. Here's my scenario: Individual hardware "component" classes obey interface contracts for each hardware type. Previously, component instances were orchestrated by a single monolithic InstrumentController class, which relied heavily on configuration + branching logic for executing a specific acquisition sequence. After an iteration, I have a separate controller for each component, with these controllers all managed by a small InstrumentControllerBase (or its derivatives). The composite system will receive "input" either programmatically or via inter-hardware component triggering - in either case these interactions are routed to, and handled by, the appropriate controller. So, I have something that feels MVC-esque, but I don't know if that's because I'm forcing the point. With little direct MVC experience in application development, it's hard to know if I'm just trying to make my scenario fit MVC, where another pattern might be a good alternative or complimentary. My problem is, search results and wiki documentation of these family of patterns seems to immediately drop me into GUI-specific discussions. I understand "M means Model data and the V means View" - but do you call the superset pattern? Component-Commander-Controller? Whence can I exhume examples exemplary?

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  • A specific data structure

    - by user550413
    Well, this question is a bit specific but I think there is some general idea in it that I can't get it. Lets say I got K servers (which is a constant that I know its size). I have a program that get requests and every request has an id and server id that will handle it. I have n requests - unknown size and can be any number. I need a data structure to support the next operations within the given complexity: GetServer - the function gets the request ID and returns the server id that is supposed to handle this request at the current situation and not necessarily the original server (see below). Complexity: O(log K) at average. KillServer - the function gets as input a server id that should be removed and another server id that all the requests of the removed server should be passed to. Complexity: O(1) at the worst case. -- Place complexity for all the structure is O(K+n) -- The KillServer function made me think using a Union-Find as I can do the union in O(1) as requested but my problem is the first operation. Why it's LogK? Actually, no matter how I "save" the requests if I want to access to any request (lets say it's an AVL tree) so the complexity will be O(log n) at the worst case and said that I can't assume Kn (and probably K Tried thinking about it a couple of hours but I can't find any solution. Known structures that can be used are: B+ tree, AVL tree, skip list, hash table, Union-Find, rank tree and of course all the basics like arrays and such.

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  • Do I need a spatial index in my database?

    - by Sanoj
    I am designing an application that needs to save geometric shapes in a database. I haven't choosen the database management system yet. In my application, all database queries will have an bounding box as input, and as output I want all shapes within that database. I know that databases with a spatial index is used for this kind of application. But in my application there will not be any queries of type "give me objects nearby x/y" or other more complex queries that are useful in a GIS application. I am planning of having a database without a spatial index and have queries looking like: SELECT * FROM shapes WHERE x < max_x AND x > min_x AND y < max_y AND y > min_y And have an index on the columns x (double) and y (double). As long I can see, I don't really need a database with an spatial index, howsoever my application is close to that kind of applications. And even if I would like to have nearby queries, then I could create a big enough bounding box around that point. Or will this lead to poor performance? Do I really need a spatial database? And when is a spatial index needed?

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  • Understanding Basic Prototyping & Updating Key/Value pairs

    - by JordanD
    First time poster, long time lurker. I'm trying to learn some more advanced features of .js, and have two ojectives based on the pasted code below: I would like to add methods to a parent class in a specific way (by invoking prototype). I intend to update the declared key/value pairs each time I make an associated method call. execMTAction as seen in TheSuper will execute each function call, regardless. This is by design. Here is the code: function TheSuper(){ this.options = {componentType: "UITabBar", componentName: "Visual Browser", componentMethod: "select", componentValue: null}; execMTAction(this.options.componentType, this.options.componentName, this.options.componentMethod, this.options.componentValue); }; TheSuper.prototype.tapUITextView = function(val1, val2){ this.options = {componentType: "UITextView", componentName: val1, componentMethod: "entertext", componentValue: val2}; }; I would like to execute something like this (very simple): theSuper.executeMTAction(); theSuper.tapUITextView("a", "b"); Unfortunately I am unable to overwrite the "this.options" in the parent, and the .tapUITextView method throws an error saying it cannot find executeMTAction. All I want to do, like I said, is to update the parameters in the parent, then have executeMTAction run each time I make any method call. That's it. Any thoughts? I understand this is basic but I'm coming from a long-time procedural career and .js seems to have this weird confluence of oo/procedural that I'm having a bit of difficulty with. Thanks for any input!

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  • Confusion with a while statement evaluating if a number is triangular

    - by Darkkurama
    I've been having troubles trying to figure out how to solve a function. I've been assigned the development of a little programme which tells if a number is "triangular" (a number is triangular when the addition of certain consecutive numbers in the [1,n] interval is n. Following the definition, the number 10 is triangular, because in the [1,10] interval, 1+2+3+4=10). I've coded this so far: class TriangularNumber{ boolean numTriangular(int n) { boolean triangular = false; int i = n; while(n>=0 && triangular){ //UE06 is a class which contains the function "f0", which makes the addition of all the numbers in a determined interval UE06 p = new UE06(); if ((p.f0(1, i))==n) triangular = true; else i=i-1; } return triangular; } boolean testTriangular = numTriangular(10) == true && numTriangular(7) == false && numTriangular(6) == true; public static void main(String[] args){ TriangularNumber p = new TriangularNumber(); System.out.println("testTriangular = " + p.testTriangular); } } According to those boolean tests I made, the function is wrong. As I see the function, it goes like this: I state that the input number in the initial state isn't triangular (triangular=false) and i=n (determining the interval [1,i] where the function is going to be evaluated While n is greater or equals 0 and the number isn't triangular, the loop starts The loop goes like this: if the addition of all the numbers in the [1,i] interval is n, the number is triangular, causing the loop to end. If that statement is false, i goes from i to (i-1), starting the loop again with that particular interval, and so on till the addition is n. I can't spot the error in my "algorithm", any advice? Thanks!

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  • Add new Formelemts and transform it with jqtransform

    - by user545782
    I'm just trying to change my formfields with jqtransform. With the following Javascript Code, i add new formfields: <script type="text/javascript"> $(function() { var scntDiv = $('#p_scents'); var i = $('#p_scents p').size() + 1; $('#addScnt').live('click', function() { if(i < 4){ $('<p>\n\ <label for="p_scnts">\n\ <input type="text" id="p_scnt" size="17" name="fmac' + i +'[]" value="" />\n\ <select name="fmac' + i +'[]" size="1" id="p_scnt_a">\n\ <option selected value="K">KABEL</option>\n\ <option value="W">WLAN</option>\n\ <option value="V">VPN</option>\n\ </select>\n\ </label>\n\ </p>').appendTo(scntDiv); i++; } if(i > 3 ){ $('#showaddmac').hide(); } return false; }); $('#remScnt').live('click', function() { if( i > 2 ) { $(this).parents('p').remove(); i--; } if(i < 4 ){ $('#showaddmac').show(); } return false; }); }); </script> this works with out problemes, but the new fields will be not transformed. Does anyone know a solution to the problem? Sry for my bad english :)

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  • Call 32-bit or 64-bit program from bootloader

    - by user1002358
    There seems to be quite a lot of identical information on the Internet about writing the following 3 bootloaders: Infinite loop jmp $ Print a single character Print "Hello World". This is fantastic, and I've gone through these 3 variations with very little trouble. I'd like to write some 32- or 64-bit code in C and compile it, and call that code from the bootloader... basically a bootloader that, for example, sets the computer up to run some simple numerical simulation. I'll start by listing primes, for example, and then maybe some input/output from the user to maybe compute a Fourier transform. I don't know. I haven't found any information on how to do this, but I can already foresee some problems before I even begin. First of all, compiling a C program compiles it into one of several different files, depending on the target. For Windows, it's a PE file. For Linux, it's a .out file. These files are both quite different. In my instance, the target isn't Windows or Linux, it's just whatever I have written in the bootloader. Secondly, where would the actual code reside? The bootloader is exactly 512 bytes, but the program I write in C will certainly compile to something much larger. It will need to sit on my (virtual) hard disk, probably in some sort of file system (which I haven't even defined!) and I will need to load the information from this file into memory before I can even think about executing it. But from my understanding, all this is many, many orders of magnitude more complex than a 12-line "Hello World" bootloader. So my question is: How do I call a large 32- or 64-bit program (written in C/C++) from my 16-bit bootloader.

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  • How to manipulate string to delete quotes?

    - by user1751581
    I am trying to manipulate a string so that any quotes (") within <a href> and <\a> get taken out... Sorry if its been asked before but I just can't get it to work! By the way, I am POSTing the data from a form and then manipulating the string. This is basically html but its in the form of a string, and I want to take out quotes on things like images and links... Another thing is, I do not want to escape the quotes because that would break the link... And the whole point is that the html can be used and work fine... But now, something is automatically creating a second set of quotes inside the normal quotes, like this: <a href="\"http://www.example.com/\""></a> Example input would be: <p><a href="http://www.example.com">example</a></p> Heres how it appears when I echo it however: <p><a href=\"http://www.example.com\">example</a></p> Heres how I want it to look: <p><a href="http://www.example.com">example</a></p> So I would actually be trying to get rid of the (/) my bad...

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  • GNU Makefile: multiple outputs from single rule + preventing intermediate files from being deleted

    - by makesaurus
    This is sort of a continuation of question from link text. The problem is that there is a rule generating multiple outputs from a single input, and the command is time-consuming so we would prefer to avoid recomputation. Now there is an additional twist, that we want to keep files from being deleted as intermediate files, and rules involve wildcards to allow for parameters. The solution suggested was that we set up the following rule: file-a.out: program file.in ./program file.in file-a.out file-b.out file-c.out file-b.out: file-a.out @ file-c.out: file-b.out @ Then, calling make file-c.out creates both and we avoid issues with running make in parallel with -j switch. All fine so far. The problem is the following. Because the above solution sets up a chain in the DAG, make considers it differently; the files file-a.out and file-b.out are treated as intermediate files, and they by default get deleted as unnecessary as soon as file-c.out is ready. A way of avoiding that was mentioned somewhere here, and consists of adding file-a.out and file-b.out as dependencies of a target .SECONDARY, which keeps them from being deleted. Unfortunately, this does not solve my case because my rules use wildcard patters; specifically, my rules look more like this: file-a-%.out: program file.in ./program $* file.in file-a-$*.out file-b-$*.out file-c-$*.out file-b-%.out: file-a-%.out @ file-c-%.out: file-b-%.out @ so that one can pass a parameter that gets included in the file name, for example by running make file-c-12.out The solution that make documentation suggests is to add these as implicit rules to the list of dependencies of .PRECIOUS, thus keeping these files from being deleted. The solution with .PRECIOUS works, but it also prevents these files from being deleted when a rule fails and files are incomplete. Is there any other way to make this work?

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  • Adding to the DOM via Prototype works in Chrome but not Firefox?

    - by zaczap
    I've been working on some Javascript code to add rows to a table dynamically (a small task management system) and it works perfectly in Chrome but not in Firefox. Code in question: var task = new Element('tr', {id:arg}); task.innerHTML = "<td class='notes'>asd</td><td class='check'>*</td>"; //task.innerHTML = "<td class='notes'>&nbsp;</td><td class='check'><input type='checkbox' onclick=\"javascript:complete('"+task.id+"')\" /></td><td class='description'>asd</td><td class='start'>&nbsp;</td><td class='due'></td>"; $('tasks').insert(task); // the commented line above is what the code was originally that does work in chrome When I look at the HTML model in the Firefox debugger, all that is added is: <tr id="arg"><td>asd*</td></tr> Figuring that Chrome might be better at interpreting innerHTML into DOM elements than Firefox, I changed the code to make td elements and add them to my tr element but that didn't improve the situation at all.

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  • Making IE "forget" information entered in form when using back button.

    - by typoknig
    I have a page with a form where many of the fields are populated from variables passed in the URL. Those fields are disabled (NON-EDITABLE) and are only there for the user to view. The remaining fields require user input and are NOT disabled (EDITABLE). When the form is submitted a confirmation page comes up. It may be the case that the user needs to submit several of these forms where the NON-EDITABLE information is identical from form to form, so being able to go back to the form page from the confirmation page would save a lot of time. The way I want this to work is when a user presses the back button all the NON-EDITABLE fields are populated, but the EDITABLE fields are blank. This is what Firefox is doing, but IE8 is does not "forget" what has been entered in the EDITABLE fields. To disable the cache the following appears at the beginning of my page AND at the end of my page. <head> <meta http-equiv="Pragma" content="no-cache"/> <meta http-equiv="Cache-Control" content="no-store"/> <head/> What more must I do to make IE forget what was entered in the EDITABLE fields when the back button is pressed? All of my pages are generated with PHP if that matters. EDIT: It appears to me that this is a problem of IE caching my page even though I have told it not to. Are my meta tags correct? Do I need to do something else to prevent IE from caching my page?

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  • MVC JsonResult with the [Authorize] attribute going to Logon but not displaying the view

    - by likestoski
    I am seeing odd behavior with MVC 3 methods that return a JsonResult when used with the Authorize attribute. What looks like happens is the Authorize is correctly evaluated when I am not logged in but instead of redirecting to the logon form the Json response is the logon form. Is there an addition attribute that directs the response to not return a value but instead redirect the user to the logon form, preferebly with the correct returnUrl value? What I did as a demo was to setup a new MVC3 site and added AspNetMembership to my DB using the aspnet_regsql.exe command. All that is setup and logging me in correctly. The behavior of the JsonResult doesn't seem right and I'm hoping I have just missed an attribute to make it work properly. Any help is greatly appreciated, thanks in advance. Here is the Account Controller (leaving out the Post action which is not part of this question). public class AccountController : Controller { public ActionResult LogOn() { return View(); } [Authorize] public JsonResult AuthorizedAction() { return Json("Only returns if I am authorized"); } } Here is the Html markup: <script src="@Url.Content("~/Scripts/jquery-ui-1.8.11.min.js")" type="text/javascript"></script> <script type="text/javascript"> $(document).ready(function () { $("#btnTest").click(function () { $.ajax({ type: "POST", url: "Account/AuthorizedAction", data: {}, success: function (result) { $("#testMe").html(result); }, error: function (result) { $("#testMe").html('Something broke in the ajax request'); } }); }); }); </script> <input type="button" id="btnTest" value="Test me" /> <div id="testMe">I have initial text</div> The Result: 1) When logged in I get 'Only returns if I am authorized' in my test div 2) When not logged and I have a break point in my Logon() method I see this value Request["returnUrl"] "/Account/AuthorizedAction" The test div I have displays the logon form :) this seems like I'm just not handling this properly.

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  • How to make buttons in python/pygame?

    - by user1334014
    I'm making a game in pygame and on the first screen I want there to be buttons that you can press to (i) start the game, (ii) load a new screen with instructions, and (iii) exit the program. I've found this code online for button making, but I don't really understand it (I'm not that good at object oriented programming). If I could get some explanation as to what it's doing that would be great. Also, when I use it and try to open a file on my computer using the file path, I get the error sh: filepath :Permission denied, which I don't know how to solve. #load_image is used in most pygame programs for loading images def load_image(name, colorkey=None): fullname = os.path.join('data', name) try: image = pygame.image.load(fullname) except pygame.error, message: print 'Cannot load image:', fullname raise SystemExit, message image = image.convert() if colorkey is not None: if colorkey is -1: colorkey = image.get_at((0,0)) image.set_colorkey(colorkey, RLEACCEL) return image, image.get_rect() class Button(pygame.sprite.Sprite): """Class used to create a button, use setCords to set position of topleft corner. Method pressed() returns a boolean and should be called inside the input loop.""" def __init__(self): pygame.sprite.Sprite.__init__(self) self.image, self.rect = load_image('button.png', -1) def setCords(self,x,y): self.rect.topleft = x,y def pressed(self,mouse): if mouse[0] > self.rect.topleft[0]: if mouse[1] > self.rect.topleft[1]: if mouse[0] < self.rect.bottomright[0]: if mouse[1] < self.rect.bottomright[1]: return True else: return False else: return False else: return False else: return False def main(): button = Button() #Button class is created button.setCords(200,200) #Button is displayed at 200,200 while 1: for event in pygame.event.get(): if event.type == MOUSEBUTTONDOWN: mouse = pygame.mouse.get_pos() if button.pressed(mouse): #Button's pressed method is called print ('button hit') if __name__ == '__main__': main() Thank you to anyone who can help me.

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  • Checkbox not checkable in dialog ui

    - by Sable Foste
    I am trying to solve a z-index problem with the jQuery UI Dialog, similar to question Can't select or deselect checkboxes inside jQuery UI Modal Dialog , knowing there is a bug report out there. So in trying to up the z-index as recommended, I added the following code: $('#interface').click(function(evform){ $('#interface').prop('z-index')=99999; }); where the chrome and firefox console.log states: Uncaught ReferenceError: Invalid left-hand side in assignment HOWEVER, despite the error, the checkbox now works (throwing the console error every time). If I remove the offending line, the checkbox becomes "unclickable". How can I properly code this? My HTML: <div id="dialog" title="Loading..."> <p id="interface">Loading...</p> </div> (by the way, I tried adding inline style to the <p>, and it didn't work: <p id="interface" style="z-index:99999">Loading...</p> And with AJAX, I replace the contents of '#interface' with valid checkbox html such as: <label for="right"> <input name="right" type="checkbox"> </label> and I have the usual jQuery/Dialog UI files included. One final note, I tried to get creative, since this wasn't working and manually switch the checkbox by: if ($(evform.target).prop('type')=="checkbox"){ $(evform.target).checked; } Thank you to anyone willing to help me figure this out!

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  • How can I create an instance of a class that I can use is more than one place in c#

    - by user1743574
    So I've been working on a class that details students of a university. I have one button that sets the details to a new instance of a class, and another to check if the student passed, through a method in my Class. The problem is that I create an instance of a class in the first button to add the values from what the user input, but I cannot use the second button to access the instance of the class created in the first button. private void button3_Click(object sender, EventArgs e) { Student student1 = new Student(); label1.Text = student1.text(); if (student1.hasPassed() == true) { passfailtextbox.Text = "Pass"; } else { passfailtextbox.Text = "Fail"; } } private void button1_Click(object sender, EventArgs e) { Student student1 = new Student(); student1.FirstName = firstnamebox.Text; student1.SecondName = secondnamebox.Text; student1.DateofBirth = DateTime.Parse(dobtextbox.Text).Date; student1.Course = coursetextbox.Text; student1.MatriculationNumber = int.Parse(matriculationtextbox.Text); student1.YearMark = double.Parse(yearmarktextbox.Text); } public Boolean hasPassed() { if (YearMark < 40) { return false; } else { return true; } } public string text() { return "Student" + " " + firstname + " " + secondname + " " + course + " " + dob.ToString() + " " + matriculationnumber.ToString() + " " + yearmark.ToString() ; }

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  • C++, inject additional data in a method

    - by justik
    I am adding the new modul in some large library. All methods here are implemented as static. Let mi briefly describe the simplified model: typedef std::vector<double> TData; double test ( const TData &arg ) { return arg ( 0 ) * sin ( arg ( 1 ) + ...;} double ( * p_test ) ( const TData> &arg) = &test; class A { public: static T f1 (TData &input) { .... //some computations B::f2 (p_test); } }; Inside f1() some computations are perfomed and a static method B::f2 is called. The f2 method is implemented by another author and represents some simulation algorithm (example here is siplified). class B { public: static double f2 (double ( * p_test ) ( const TData &arg ) ) { //difficult algorithm working p_test many times double res = p_test(arg); } }; The f2 method has a pointer to some weight function (here p_test). But in my case some additional parameters computed in f1 for test() methods are required double test ( const TData &arg, const TData &arg2, char *arg3.... ) { } How to inject these parameters into test() (and so to f2) to avoid changing the source code of the f2 methods (that is not trivial), redesign of the library and without dirty hacks :-) ? The most simple step is to override f2 static double f2 (double ( * p_test ) ( const TData &arg ), const TData &arg2, char *arg3.... ) But what to do later? Consider, that methods are static, so there will be problems with objects. Thanks for your help.

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  • C++ reference variable again!!!

    - by kumar_m_kiran
    Hi All, I think most would be surprised about the topic again, However I am referring to a book "C++ Common Knowledge: Essential Intermediate Programming" written by "Stephen C. Dewhurst". In the book, he quotes a particular sentence (in section under Item 5. References Are Aliases, Not Pointers), which is as below A reference is an alias for an object that already exists prior to the initialization of the reference. Once a reference is initialized to refer to a particular object, it cannot later be made to refer to a different object; a reference is bound to its initializer for its whole lifetime Can anyone please explain the context of "cannot later be made to refer to a different object" Below code works for me, #include <iostream> using namespace std; int main(int argc, char *argv[]) { int i = 100; int& ref = i; cout<<ref<<endl; int k = 2000; ref = k; cout<<ref<<endl; return 0; } Here I am referring the variable ref to both i and j variable. And the code works perfectly fine. Am I missing something? I have used SUSE10 64bit linux for testing my sample program. Thanks for your input in advance.

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  • Why does Go not seem to recognize size_t in a C header file?

    - by Graeme Perrow
    I am trying to write a go library that will act as a front-end for a C library. If one of my C structures contains a size_t, I get compilation errors. AFAIK size_t is a built-in C type, so why wouldn't go recognize it? My header file looks like: typedef struct mystruct { char * buffer; size_t buffer_size; size_t * length; } mystruct; and the errors I'm getting are: gcc failed: In file included from <stdin>:5: mydll.h:4: error: expected specifier-qualifier-list before 'size_t' on input: typedef struct { char *p; int n; } _GoString_; _GoString_ GoString(char *p); char *CString(_GoString_); #include "mydll.h" I've even tried adding either of // typedef unsigned long size_t or // #define size_t unsigned long in the .go file before the // #include, and then I get "gcc produced no output". I have seen these questions, and looked over the example with no success.

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  • Logging in with sha1() encryption.

    - by Samir Ghobril
    Hey guys, I added this to my sign up code : $password=mysql_real_escape_string(sha1($_POST['password'])); and now it inserts the password into the database while its encrypted. But signing in doesn't seem to work anymore. Here is the login code. function checklogin($username, $password){ global $mysqli; $password=sha1($password); $result = $mysqli->prepare("SELECT * FROM users WHERE username = ? and password=?"); $result->bind_param("ss", $username, $password); $result->execute(); if($result != false){ $dbArray=$result->fetch(); if(!$dbArray){ echo '<p class="statusmsg">The username or password you entered is incorrect, or you haven\'t yet activated your account. Please try again.</p><br/><input class="submitButton" type="button" value="Retry" onClick="location.href='."'login.php'\">"; return; } $_SESSION['username']=$username; if(isset($_POST['remember'])){ setcookie("jmuser",$username,time()+60*60*24*356); setcookie("jmpass",$password ,time()+60*60*24*356); } redirect(); }

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  • How to prevent onclick statements from being executed?

    - by ryanli
    I want to use an event listener for preventing the onclick statement of a submit button, however, using event.preventDefault() doesn't work as intended. The code is like this: <?xml version="1.0" encoding="utf-8"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <script type="application/x-javascript"> function addListener() { document.getElementById("submit").addEventListener("click", function(ev) { alert("listener"); ev.preventDefault(); }, false); } </script> <title></title> </head> <body onload="addListener();"> <form id="form" method="post" target=""> <input type="submit" id="submit" onclick="alert('onclick')" value="test" /> </form> </body> </html> The expected behaviour is only "listener" will be alerted, but in practice (Firefox 3.7a5pre), "onclick" and "listener" are both alerted, in the given order. It seems that onclick is being executed before the listener, so event.preventDefault() doesn't work. Is there a way to prevent onclick from being executed?

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  • Performance difference between functions and pattern matching in Mathematica

    - by Samsdram
    So Mathematica is different from other dialects of lisp because it blurs the lines between functions and macros. In Mathematica if a user wanted to write a mathematical function they would likely use pattern matching like f[x_]:= x*x instead of f=Function[{x},x*x] though both would return the same result when called with f[x]. My understanding is that the first approach is something equivalent to a lisp macro and in my experience is favored because of the more concise syntax. So I have two questions, is there a performance difference between executing functions versus the pattern matching/macro approach? Though part of me wouldn't be surprised if functions were actually transformed into some version of macros to allow features like Listable to be implemented. The reason I care about this question is because of the recent set of questions (1) (2) about trying to catch Mathematica errors in large programs. If most of the computations were defined in terms of Functions, it seems to me that keeping track of the order of evaluation and where the error originated would be easier than trying to catch the error after the input has been rewritten by the successive application of macros/patterns.

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  • C++ STL question related to insert iterators and sets

    - by rshepherd
    #include #include #include #include using namespace std; class MyContainer { public: string value; MyContainer& operator=(const string& s) { this->value = s; return *this; } }; int main() { list<string> strings; strings.push_back("0"); strings.push_back("1"); strings.push_back("2"); set<MyContainer> containers; copy(strings.begin(), strings.end(), inserter(containers, containers.end())); } The preceeding code does not compile. In typical STL style the error output is verbose and difficult to understand. The key part seems to be this... /usr/include/c++/4.4/bits/stl_algobase.h:313: error: no match for ‘operator=’ in ‘__result.std::insert_iterator::operator* [with _Container = std::set, std::allocator ]() = __first.std::_List_iterator::operator* [with _Tp = std::basic_string, std::allocator ]()’ ...which I interpet to mean that the assignment operator needed is not defined. I took a look at the source code for insert_iterator and noted that it has overloaded the assignment operator. The copy algorithm must uses the insert iterators overloaded assignment operator to do its work(?). I guess that because my input iterator is on a container of strings and my output iterator is on a container of MyContainers that the overloaded insert_iterator assignment operator can no longer work. This is my best guess, but I am probably wrong. So, why exactly does this not work and how can I accomplish what I am trying to do?

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