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  • is there a Universal Model for languages?

    - by Smandoli
    Many programming languages share generic and even fairly universal features. For example, if you compared Java, VB6, .NET, PHP, Python, then you would find common functions such as control structures, numeric and string manipulation, etc. What has been done to define these features at a meta-language (or language-agnostic) level? UML offers a descriptive reference of software in every aspect, but the real-world focus seems to be data processes. Is UML relevant? I'm not asking "Why we don't have a single language that replaces the current plethora." We need many different tools (at least in this eon). I'm not asking that all languages fit a template -- assembly vs. compiled languages are different enough to make that unfeasible (and some folks call HTML a language, though I wouldn't). Any attempt would start with a properly narrow scope. In line with this, I wouldn't expect the model to cover even a small selection with full validity. I would expect however that such a model could be used to transpose from one language to another (with limited goals -- think jist translation).

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  • Protected and Private methods

    - by cabaret
    I'm reading through Beginning Ruby and I'm stuck at the part about private and protected methods. This is a newbie question, I know. I searched through SO for a bit but I couldn't manage to find a clear and newbie-friendly explanation of the difference between private and protected methods. The book gives two examples, the first one for private methods: class Person def initialize(name) set_name(name) end def name @first_name + ' ' + @last_name end private def set_name(name) first_name, last_name = name.split(/\s+/) set_first_name(first_name) set_last_name(last_name) end def set_first_name(name) @first_name = name end def set_last_name(name) @last_name = name end end In this case, if I try p = Person.new("Fred Bloggs") p.set_last_name("Smith") It will tell me that I can't use the set_last_name method, because it's private. All good till there. However, in the other example, they define an age method as protected and when I do fred = Person.new(34) chris = Person.new(25) puts chris.age_difference_with(fred) puts chris.age It gives an error: :20: protected method 'age' called for #<Person:0x1e5f28 @age=25> (NoMethodError) I honestly fail to see the difference between the private and protected methods, it sounds the same to me. Could someone provide me with a clear explanation so I'll never get confused about this again? I'll provide the code for the second example if necessary.

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  • Catching / blocking SIGINT during system call

    - by danben
    I've written a web crawler that I'd like to be able to stop via the keyboard. I don't want the program to die when I interrupt it; it needs to flush its data to disk first. I also don't want to catch KeyboardInterruptedException, because the persistent data could be in an inconsistent state. My current solution is to define a signal handler that catches SIGINT and sets a flag; each iteration of the main loop checks this flag before processing the next url. However, I've found that if the system happens to be executing socket.recv() when I send the interrupt, I get this: ^C Interrupted; stopping... // indicates my interrupt handler ran Traceback (most recent call last): File "crawler_test.py", line 154, in <module> main() ... File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/socket.py", line 397, in readline data = recv(1) socket.error: [Errno 4] Interrupted system call and the process exits completely. Why does this happen? Is there a way I can prevent the interrupt from affecting the system call?

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  • Using struts.xml with convention plugin

    - by David Alt
    This seems like it should be easy to do, but I just can make it work. I'm hooked on the convention plugin in Struts 2.1. However, I need to define some package-level configuration such as a new interceptor stack and exception mappings. I'd like to use the struts.xml file for this, but I can't get the convention-based packages matched to the struts.xml packages. My struts.xml looks like: <struts> <constant name="struts.convention.default.parent.package" value="default"/> <package name="default" extends="struts-default"> </package> <package name="root" namespace="/" extends="struts-default"> <action name="index"> <result>/index.jsp</result> </action> </package> <package name="my.package.actions.myaccount" namespace="/myaccount" extends="struts-default"> <interceptors> <interceptor name="authenticationInterceptor" class="my.package.interceptors.AuthenticationInterceptor"/> <interceptor-stack name="secureStack"> <interceptor-ref name="authenticationInterceptor"/> <interceptor-ref name="defaultStack"/> </interceptor-stack> </interceptors> <default-interceptor-ref name="secureStack"/> </package> </struts> I have my interceptor in: /src/my/package/interceptors and my actions in: /src/my/package/actions/myaccount

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  • Java enums in generic type

    - by Marcin Cylke
    Hi, I'd like to create a generic enum-based mapper for IBatis. I'm doing this with the below code. This does have compile time errors, which I don't know how to fix. Maybe my solution is just plain wrong (keep in mind the use of IBatis), in such case please suggest something better. Any help appreciated. What I want to achieve is to define subsequent mappers as: public class XEnumTypeHandler extends CommonEnumTypeHandler<X> { } The current code: public class CommonEnumTypeHandler<T extends Enum> implements TypeHandlerCallback { public void setParameter(ParameterSetter ps, Object o) throws SQLException { if (o.getClass().isAssignableFrom(**T**)) { ps.setString(((**T**) o).value().toUpperCase()); } else throw new SQLException("Excpected ParameterType object than: " + o); } public Object getResult(ResultGetter rs) throws SQLException { Object o = valueOf(rs.getString()); if (o == null) throw new SQLException("Unknown parameter type: " + rs.getString()); return o; } public Object valueOf(String s) { for (T pt : T.**values()**) { if (pt.**value()**.equalsIgnoreCase(s)) return pt; } return null; } } I've added error markings to the above code, the error messages are in order: T cannot be resolved The method value() is undefined for the type T The method values() is undefined for the type T The method values() is undefined for the type T

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  • ASP.NET MVC application architecture "guidelines"

    - by Joe Future
    I'm looking for some feedback on my ASP.NET MVC based CMS application architecture. Domain Model - depends on nothing but the System classes to define types. For now, mostly anemic. Repository Layer - abstracted data access, only called by the services layer Services Layer - performs business logic on domain models. Exposes view models to the controllers. ViewModelMapper - service that translates back and forth between view models and domain models Controllers - super thin "traffic cop" style functionality that interacts with the service layer and only talks in terms of view models, never domain models My domain model is mostly used as data transfer (DTO) objects and has minimal logic at the moment. I'm finding this is nice because it depends on nothing (not even classes in the services layer). The services layer is a bit tricky... I only want the controllers to have access to viewmodels for ease of GUI programming. However, some of the services need to talk to each other. For example, I have an eventing service that notifies other listener services when content is tagged, when blog posts are created, etc. Currently, the methods that take domain models as inputs or return them are marked internal so they can't be used by the controllers. Sounds like overkill? Not enough abstraction? I'm mainly doing this as a learning exercise in being strict about architecture, not for an actual product, so please no feedback along the lines of "right depends on what you want to do". thanks! Jason

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  • Are there pitfalls to using static class/event as an application message bus

    - by Doug Clutter
    I have a static generic class that helps me move events around with very little overhead: public static class MessageBus<T> where T : EventArgs { public static event EventHandler<T> MessageReceived; public static void SendMessage(object sender, T message) { if (MessageReceived != null) MessageReceived(sender, message); } } To create a system-wide message bus, I simply need to define an EventArgs class to pass around any arbitrary bits of information: class MyEventArgs : EventArgs { public string Message { get; set; } } Anywhere I'm interested in this event, I just wire up a handler: MessageBus<MyEventArgs>.MessageReceived += (s,e) => DoSomething(); Likewise, triggering the event is just as easy: MessageBus<MyEventArgs>.SendMessage(this, new MyEventArgs() {Message="hi mom"}); Using MessageBus and a custom EventArgs class lets me have an application wide message sink for a specific type of message. This comes in handy when you have several forms that, for example, display customer information and maybe a couple forms that update that information. None of the forms know about each other and none of them need to be wired to a static "super class". I have a couple questions: fxCop complains about using static methods with generics, but this is exactly what I'm after here. I want there to be exactly one MessageBus for each type of message handled. Using a static with a generic saves me from writing all the code that would maintain the list of MessageBus objects. Are the listening objects being kept "alive" via the MessageReceived event? For instance, perhaps I have this code in a Form.Load event: MessageBus<CustomerChangedEventArgs>.MessageReceived += (s,e) => DoReload(); When the Form is Closed, is the Form being retained in memory because MessageReceived has a reference to its DoReload method? Should I be removing the reference when the form closes: MessageBus<CustomerChangedEventArgs>.MessageReceived -= (s,e) => DoReload();

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  • Summation loop program in Pascal

    - by user2526598
    I am having a bit of an issue with this problem. I am taking a Pascal programming class and this problem was in my logic book. I am required to have the user enter a series of (+) numbers and once he/she enters a (-) number, the program should find the sum of all the (+) numbers. I accomplished this, but now I am attempting part two of this problem, which requires me to utilize a nested loop to run the program x amount of times based on the user's input. The following code is what I have so far and honestly I am stumped: program summation; //Define main program's variables var num, sum, numRun : integer; //Design procedure that will promt user for number of runs procedure numRunLoop ( var numRun : integer ); begin writeln('How many times shall I run this program?'); readln(numRun); end; //Design procedure that will sum a series of numbers //based on user input procedure numPromptLoop( numRun : integer; var num : integer ); var count : integer; begin //Utilize for to establish run limit for count := 1 to numRun do begin //Use repeat to prompt user for numbers repeat writeln('Enter a number: '); readln(num); //Tells program when to sum if num >= 0 then sum := sum + num; until num < 0; end; end; //Design procedure that will display procedure addItion( sum : integer ); begin writeln('The sum is; ', sum); end; begin numRunLoop(numRun); numPromptloop(numRun, num); addItion(sum); readln(); end.

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  • iPhone: AppStore InAppPurchase Connects in Simulator but Not on Device

    - by riteshkumar1905
    I am having trouble connecting to the AppStore from within my application. Everything runs fine in the Simulator but when I run on device the app cannot connect to the Appstore. Here is the code that connects to the Appstore #import "BuyController.h"#import "InAppPurchaseManager.h" #import "SKProducts.h" #define kInAppPurchaseProUpgradeProductId @"com.vigyaapan.iWorkOut1" @implementation BuyController - (IBAction)buy:(id)sender{ /* get the product description (defined in early sections)*/ //[self requestProUpgradeProductData]; if ([SKPaymentQueue canMakePayments]) { InAppPurchaseManager *Observer = [[InAppPurchaseManager alloc] init]; [[SKPaymentQueue defaultQueue] addTransactionObserver:Observer]; //NSURL *sandboxStoreURL = [[NSURL alloc]initWithString:@"http://sandbox.itunes.apple.com/verifyReceipt"]; //[[UIApplication sharedApplication]openURL:[NSURL URLWithString:@"http://sandbox.itunes.apple.com"]]; [[UIApplication sharedApplication] openURL:[NSURL URLWithString:@"http://phobos.apple.com/WebObjects/ com.vigyaapan.iWorkOut1?id=9820091347&;amp;amp;amp;amp;mt=8"]]; //[[UIApplication sharedApplication] openURL:[NSURL URLWithString:@"http://phobos.apple.com/WebObjects/MZStore.woa/wa/viewSoftware?id=301349397&;amp;amp;amp;amp;mt=8"]]; SKPayment *payment = [SKPayment paymentWithProductIdentifier:@"com.vigyaapan.iWorkOut1"]; [[SKPaymentQueue defaultQueue] addPayment:payment]; } else { UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"MyApp" message:@"You are not authorized to purchase from AppStore" delegate:self cancelButtonTitle:@"OK" otherButtonTitles: nil]; [alert show]; [alert release]; } //return [SKPaymentQueue canMakePayments];} SKPayment *payment = [SKPayment paymentWithProductIdentifier:kInAppPurchaseProUpgradeProductId]; [[SKPaymentQueue defaultQueue] addPayment:payment]; //[self requestProUpgradeProductData]; /* get the product description (defined in early sections)*/ } @end

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  • Using recursion to to trim a binary tree based on a given min and max value

    - by Justin
    As the title says, I have to trim a binary tree based on a given min and max value. Each node stores a value, and a left/right node. I may define private helper methods to solve this problem, but otherwise I may not call any other methods of the class nor create any data structures such as arrays, lists, etc. An example would look like this: overallRoot _____[50]____________________ / \ __________[38] _______________[90] / \ / _[14] [42] [54]_____ / \ \ [8] [20] [72] \ / \ [26] [61] [83] trim(52, 65); should return: overallRoot [54] \ [61] My attempted solution has three methods: public void trim(int min, int max) { rootFinder(overallRoot, min, max); } First recursive method finds the new root perfectly. private void rootFinder(IntTreeNode node, int min, int max) { if (node == null) return; if (overallRoot.data < min) { node = overallRoot = node.right; rootFinder(node, min, max); } else if (overallRoot.data > max) { node = overallRoot = node.left; rootFinder(node, min, max); } else cutter(overallRoot, min, max); } This second method should eliminate any further nodes not within the min/max, but it doesn't work as I would hope. private void cutter(IntTreeNode node, int min, int max) { if (node == null) return; if (node.data <= min) { node.left = null; } if (node.data >= max) { node.right = null; } if (node.data < min) { node = node.right; } if (node.data > max) { node = node.left; } cutter(node.left, min, max); cutter(node.right, min, max); } This returns: overallRoot [54]_____ \ [72] / [61] Any help is appreciated. Feel free to ask for further explanation as needed.

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  • Why are my events being called more than once?

    - by Arms
    In my Flash project I have a movieclip that has 2 keyframes. Both frames contain 1 movieclip each. frame 1 - Landing frame 2 - Game The flow of the application is simple: User arrives on landing page (frame 1) User clicks "start game" button User is brought to the game page (frame 2) When the game is over, the user can press a "play again" button which brings them back to step 1 Both Landing and Game movieclips are linked to separate classes that define event listeners. The problem is that when I end up back at step 1 after playing the game, the Game event listeners fire twice for their respective event. And if I go through the process a third time, the event listeners fire three times for every event. This keeps happening, so if I loop through the application flow 7 times, the event listeners fire seven times. I don't understand why this is happening because on frame 1, the Game movieclip (and I would assume its related class instance) does not exist - but I'm clearly missing something here. I've run into this problem in other projects too, and tried fixing it by first checking if the event listeners existed and only defining them if they didn't, but I ended up with unexpected results that didn't really solve the problem. I need to ensure that the event listeners only fire once. Any advice & insight would be greatly appreciated, thanks!

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  • Indentation control while developing a small python like language

    - by sap
    Hello, I'm developing a small python like language using flex, byacc (for lexical and parsing) and C++, but i have a few questions regarding scope control. just as python it uses white spaces (or tabs) for indentation, not only that but i want to implement index breaking like for instance if you type "break 2" inside a while loop that's inside another while loop it would not only break from the last one but from the first loop as well (hence the number 2 after break) and so on. example: while 1 while 1 break 2 'hello world'!! #will never reach this. "!!" outputs with a newline end 'hello world again'!! #also will never reach this. again "!!" used for cout end #after break 2 it would jump right here but since I don't have an "anti" tab character to check when a scope ends (like C for example i would just use the '}' char) i was wondering if this method would the the best: I would define a global variable, like "int tabIndex" on my yacc file that i would access in my lex file using extern. then every time i find a tab character on my lex file i would increment that variable by 1. when parsing on my yacc file if i find a "break" keyword i would decrement by the amount typed after it from the tabIndex variable, and when i reach and EOF after compiling and i get a tabIndex != 0 i would output compilation error. now the problem is, whats the best way to see if the indentation got reduced, should i read \b (backspace) chars from lex and then reduce the tabIndex variable (when the user doesn't use break)? another method to achieve this? also just another small question, i want every executable to have its starting point on the function called start() should i hardcode this onto my yacc file? sorry for the long question any help is greatly appreciated. also if someone can provide an yacc file for python would be nice as a guideline (tried looking on Google and had no luck). thanks in advance.

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  • Execute function without sending 'self' to it

    - by Sergey
    Is that possible to define a function without referencing to self this way? def myfunc(var_a,var_b) But so that it could also get sender data, like if I defined it like this: def myfunc(self, var_a,var_b) That self is always the same so it looks a little redundant here always to run a function this way: myfunc(self,'data_a','data_b'). Then I would like to get its data in the function like this sender.fields. UPDATE: Here is some code to understand better what I mean. The class below is used to show a page based on Jinja2 templates engine for users to sign up. class SignupHandler(webapp.RequestHandler): def get(self, *args, **kwargs): utils.render_template(self, 'signup.html') And this code below is a render_template that I created as wrapper to Jinja2 functions to use it more conveniently in my project: def render_template(response, template_name, vars=dict(), is_string=False): template_dirs = [os.path.join(root(), 'templates')] logging.info(template_dirs[0]) env = Environment(loader=FileSystemLoader(template_dirs)) try: template = env.get_template(template_name) except TemplateNotFound: raise TemplateNotFound(template_name) content = template.render(vars) if is_string: return content else: response.response.out.write(content) As I use this function render_template very often in my project and usually the same way, just with different template files, I wondered if there was a way to get rid of having to call it like I do it now, with self as the first argument but still having access to that object.

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  • c++ queue template

    - by Dalton Conley
    ALright, pardon my messy code please. Below is my queue class. #include <iostream> using namespace std; #ifndef QUEUE #define QUEUE /*---------------------------------------------------------------------------- Student Class # Methods # Student() // default constructor Student(string, int) // constructor display() // out puts a student # Data Members # Name // string name Id // int id ----------------------------------------------------------------------------*/ class Student { public: Student() { } Student(string iname, int iid) { name = iname; id = iid; } void display(ostream &out) const { out << "Student Name: " << name << "\tStudent Id: " << id << "\tAddress: " << this << endl; } private: string name; int id; }; // define a typedef of a pointer to a student. typedef Student * StudentPointer; template <typename T> class Queue { public: /*------------------------------------------------------------------------ Queue Default Constructor Preconditions: none Postconditions: assigns default values for front and back to 0 description: constructs a default empty Queue. ------------------------------------------------------------------------*/ Queue() : myFront(0), myBack(0) {} /*------------------------------------------------------------------------ Copy Constructor Preconditions: requres a reference to a value for which you are copying Postconditions: assigns a copy to the parent Queue. description: Copys a queue and assigns it to the parent Queue. ------------------------------------------------------------------------*/ Queue(const T & q) { myFront = myBack = 0; if(!q.empty()) { // copy the first node myFront = myBack = new Node(q.front()); NodePointer qPtr = q.myFront->next; while(qPtr != NULL) { myBack->next = new Node(qPtr->data); myBack = myBack->next; qPtr = qPtr->next; } } } /*------------------------------------------------------------------------ Destructor Preconditions: none Postconditions: deallocates the dynamic memory for the Queue description: deletes the memory stored for a Queue. ------------------------------------------------------------------------*/ ~Queue() { NodePointer prev = myFront, ptr; while(prev != NULL) { ptr = prev->next; delete prev; prev = ptr; } } /*------------------------------------------------------------------------ Empty() Preconditions: none Postconditions: returns a boolean value. description: returns true/false based on if the queue is empty or full. ------------------------------------------------------------------------*/ bool empty() const { return (myFront == NULL); } /*------------------------------------------------------------------------ Enqueue Preconditions: requires a constant reference Postconditions: allocates memory and appends a value at the end of a queue description: ------------------------------------------------------------------------*/ void enqueue(const T & value) { NodePointer newNodePtr = new Node(value); if(empty()) { myFront = myBack = newNodePtr; newNodePtr->next = NULL; } else { myBack->next = newNodePtr; myBack = newNodePtr; newNodePtr->next = NULL; } } /*------------------------------------------------------------------------ Display Preconditions: requires a reference of type ostream Postconditions: returns the ostream value (for chaining) description: outputs the contents of a queue. ------------------------------------------------------------------------*/ void display(ostream & out) const { NodePointer ptr; ptr = myFront; while(ptr != NULL) { out << ptr->data << " "; ptr = ptr->next; } out << endl; } /*------------------------------------------------------------------------ Front Preconditions: none Postconditions: returns a value of type T description: returns the first value in the parent Queue. ------------------------------------------------------------------------*/ T front() const { if ( !empty() ) return (myFront->data); else { cerr << "*** Queue is empty -- returning garbage value ***\n"; T * temp = new(T); T garbage = * temp; delete temp; return garbage; } } /*------------------------------------------------------------------------ Dequeue Preconditions: none Postconditions: removes the first value in a queue ------------------------------------------------------------------------*/ void dequeue() { if ( !empty() ) { NodePointer ptr = myFront; myFront = myFront->next; delete ptr; if(myFront == NULL) myBack = NULL; } else { cerr << "*** Queue is empty -- " "can't remove a value ***\n"; exit(1); } } /*------------------------------------------------------------------------ pverloaded = operator Preconditions: requires a constant reference Postconditions: returns a const type T description: this allows assigning of queues to queues ------------------------------------------------------------------------*/ Queue<T> & operator=(const T &q) { // make sure we arent reassigning ourself // e.g. thisQueue = thisQueue. if(this != &q) { this->~Queue(); if(q.empty()) { myFront = myBack = NULL; } else { myFront = myBack = new Node(q.front()); NodePointer qPtr = q.myFront->next; while(qPtr != NULL) { myBack->next = new Node(qPtr->data); myBack = myBack->next; qPtr = qPtr->next; } } } return *this; } private: class Node { public: T data; Node * next; Node(T value, Node * first = 0) : data(value), next(first) {} }; typedef Node * NodePointer; NodePointer myFront, myBack, queueSize; }; /*------------------------------------------------------------------------ join Preconditions: requires 2 queue values Postconditions: appends queue2 to the end of queue1 description: this function joins 2 queues into 1. ------------------------------------------------------------------------*/ template <typename T> Queue<T> join(Queue<T> q1, Queue<T> q2) { Queue<T> q1Copy(q1), q2Copy(q2); Queue<T> jQueue; while(!q1Copy.empty()) { jQueue.enqueue(q1Copy.front()); q1Copy.dequeue(); } while(!q2Copy.empty()) { jQueue.enqueue(q2Copy.front()); q2Copy.dequeue(); } cout << jQueue << endl; return jQueue; } /*---------------------------------------------------------------------------- Overloaded << operator Preconditions: requires a constant reference and a Queue of type T Postconditions: returns the ostream (for chaining) description: this function is overloaded for outputing a queue with << ----------------------------------------------------------------------------*/ template <typename T> ostream & operator<<(ostream &out, Queue<T> &s) { s.display(out); return out; } /*---------------------------------------------------------------------------- Overloaded << operator Preconditions: requires a constant reference and a reference of type Student Postconditions: none description: this function is overloaded for outputing an object of type Student. ----------------------------------------------------------------------------*/ ostream & operator<<(ostream &out, Student &s) { s.display(out); } /*---------------------------------------------------------------------------- Overloaded << operator Preconditions: requires a constant reference and a reference of a pointer to a Student object. Postconditions: none description: this function is overloaded for outputing pointers to Students ----------------------------------------------------------------------------*/ ostream & operator<<(ostream &out, StudentPointer &s) { s->display(out); } #endif Now I'm having some issues with it. For one, when I add 0 to a queue and then I output the queue like so.. Queue<double> qdub; qdub.enqueue(0); cout << qdub << endl; That works, it will output 0. But for example, if I modify that queue in any way.. like.. assign it to a different queue.. Queue<double> qdub1; Queue<double> qdub2; qdub1.enqueue(0; qdub2 = qdub1; cout << qdub2 << endl; It will give me weird values for 0 like.. 7.86914e-316. Help on this would be much appreciated!

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  • Returning the same type the function was passed

    - by Ken Bloom
    I have the following code implementation of Breadth-First search. trait State{ def successors:Seq[State] def isSuccess:Boolean = false def admissableHeuristic:Double } def breadthFirstSearch(initial:State):Option[List[State]] = { val open= new scala.collection.mutable.Queue[List[State]] val closed = new scala.collection.mutable.HashSet[State] open.enqueue(initial::Nil) while (!open.isEmpty){ val path:List[State]=open.dequeue() if(path.head.isSuccess) return Some(path.reverse) closed += path.head for (x <- path.head.successors) if (!closed.contains(x)) open.enqueue(x::path) } return None } If I define a subtype of State for my particular problem class CannibalsState extends State { //... } What's the best way to make breadthFirstSearch return the same subtype as it was passed? Supposing I change this so that there are 3 different state classes for my particular problem and they share a common supertype: abstract class CannibalsState extends State { //... } class LeftSideOfRiver extends CannibalsState { //... } class InTransit extends CannibalsState { //... } class RightSideOfRiver extends CannibalsState { //... } How can I make the types work out so that breadthFirstSearch infers that the correct return type is CannibalsState when it's passed an instance of LeftSideOfRiver? Can this be done with an abstract type member, or must it be done with generics?

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  • Passing filtering functions to Where() in LINQ-to-SQL

    - by Daniel
    I'm trying to write a set of filtering functions that can be chained together to progressively filter a data set. What's tricky about this is that I want to be able to define the filters in a different context from that in which they'll be used. I've gotten as far as being able to pass a very basic function to the Where() clause in a LINQ statement: filters file: Func<item, bool> returnTrue = (i) => true; repository file: public IQueryable<item> getItems() { return DataContext.Items.Where(returnTrue); } This works. However, as soon as I try to use more complicated logic, the trouble begins: filters file: Func<item, bool> isAssignedToUser = (i) => i.assignedUserId == userId; repository file: public IQueryable<item> getItemsAssignedToUser(int userId) { return DataContext.Items.Where(isAssignedToUser); } This won't even build because userId isn't in the same scope as isAssignedToUser(). I've also tried declaring a function that takes the userId as a parameter: Func<item, int, bool> isAssignedToUser = (i, userId) => i.assignedUserId == userId; The problem with this is that it doesn't fit the function signature that Where() is expecting: Func<item, bool> There must be a way to do this, but I'm at a loss for how. I don't feel like I'm explaining this very well, but hopefully you get the gist. Thanks, Daniel

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  • What is the best way to store site configuration data?

    - by DaveDev
    I have a question about storing site configuration data. We have a platform for web applications. The idea is that different clients can have their data hosted and displayed on their own site which sits on top of this platform. Each site has a configuration which determines which panels relevant to the client appear on which pages. The system was originally designed to keep all the configuration data for each site in a database. When the site is loaded all the configuration data is loaded into a SiteConfiguration object, and the clients panels are generated based on the content of this object. This works, but I find it very difficult to work with to apply change requests or add new sites because there is so much data to sift through and it's difficult maintain a mental model of the site and its configuration. Recently I've been tasked with developing a subset of some of the sites to be generated as PDF documents for printing. I decided to take a different approach to how I would define the configuration in that instead of storing configuration data in the database, I wrote XML files to contain the data. I find it much easier to work with because instead of reading meaningless rows of data which are related to other meaningless rows of data, I have meaningful documents with semantic, readable information with the relationships defined by visually understandable element nesting. So now with these 2 approaches to storing site configuration data, I'd like to get the opinions of people more experienced in dealing with this issue on dealing with these two approaches. What is the best way of storing site configuration data? Is there a better way than the two ways I outlined here? note: StackOverflow is telling me the question appears to be subjective and is likely to be closed. I'm not trying to be subjective. I'd like to know how best to approach this issue next time and if people with industry experience on this could provide some input.

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  • Problem with setjmp/longjmp

    - by user294732
    The code below is just not working. Can anybody point out why #define STACK_SIZE 1524 static void mt_allocate_stack(struct thread_struct *mythrd) { unsigned int sp = 0; void *stck; stck = (void *)malloc(STACK_SIZE); sp = (unsigned int)&((stck)); sp = sp + STACK_SIZE; while((sp % 8) != 0) sp--; #ifdef linux (mythrd->saved_state[0]).__jmpbuf[JB_BP] = (int)sp; (mythrd->saved_state[0]).__jmpbuf[JB_SP] = (int)sp-500; #endif } void mt_sched() { fprintf(stdout,"\n Inside the mt_sched"); fflush(stdout); if ( current_thread->state == NEW ) { if ( setjmp(current_thread->saved_state) == 0 ) { mt_allocate_stack(current_thread); fprintf(stdout,"\n Jumping to thread = %u",current_thread->thread_id); fflush(stdout); longjmp(current_thread->saved_state, 2); } else { new_fns(); } } } All I am trying to do is to run the new_fns() on a new stack. But is is showing segmentation fault at new_fns(). Can anybody point me out what's wrong.

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  • Mac OS X and static boost libs -> std::string fail

    - by Ionic
    Hi all, I'm experiencing some very weird problems with static boost libraries under Mac OS X 10.6.6. The error message is main(78485) malloc: *** error for object 0x1000e0b20: pointer being freed was not allocated *** set a breakpoint in malloc_error_break to debug [1] 78485 abort (core dumped) and a tiny bit of example code which will trigger this problem: #define BOOST_FILESYSTEM_VERSION 3 #include <boost/filesystem.hpp> #include <iostream> int main (int argc, char **argv) { std::cout << boost::filesystem::current_path ().string () << '\n'; } This problem always occurs when linking the static boost libraries into the binary. Linking dynamically will work fine, though. I've seen various reports for quite a similar OS X bug with GCC 4.2 and the _GLIBCXX_DEBUG macro set, but this one seems even more generic, as I'm neither using XCode, nor setting the macro (even undefining it does not help. I tried it just to make sure it's really not related to this problem.) Does anybody have any pointers to why this is happening or even maybe a solution (rather than using the dynamic library workaround)? Best regards, Mihai

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  • ExtJS 4 Chart Axis Display Issue in Chrome

    - by SerEnder
    I've run into an issue while using ExtJS 4.0.7. I'm trying to display a chart with two series on a Numeric/Category Chart. The chart displays correctly in Firefox, but while using Chrome (18.0.1025.142) the x axis labels are either all stacked upon each or else (when using rotate) rendered behind the chart in the specified angle. Any ideas would be appreciated. Screen shot in Firefox: Screen Shot in Chrome: And the code that's used to generate both: Ext.require(['Ext.chart.*']); Ext.onReady(function() { var iChartWidth = 800; // Defines chart width var iChartHeight = 550; // Defines chart height Ext.define('RulesCreatedModel',{ extend:'Ext.data.Model', fields:[ {name:'sHourName', type:'string'}, {name:'User_2', type:'number'}, {name:'User_1', type:'number'}, ] }); var RulesCreatedStore = Ext.create('Ext.data.Store',{ id:'RulesCreatedStore', model:'RulesCreateModel', fields: [ 'sHourName','dayNum','hour','User_2','User_1'], data:[{ 'sHourName':'3pm', 'User_1':82, 'User_2':56 },{ 'sHourName':'4pm', 'User_1':39, 'User_2':44 },{ 'sHourName':'5pm', 'User_1':80, 'User_2':14 },{ 'sHourName':'6pm', 'User_1':55, 'User_2':0, },{ 'sHourName':'7pm', 'User_1':36, 'User_2':0, },{ 'sHourName':'8pm', 'User_1':66, 'User_2':0 },{ 'sHourName':'9pm', 'User_1':39, 'User_2':0, },{ 'sHourName':'10pm', 'User_1':0, 'User_2':0 },{ 'sHourName':'11pm', 'User_1':0, 'User_2':0 },{ 'sHourName':'12am', 'User_1':0, 'User_2':0 },{ 'sHourName':'1am', 'User_1':0, 'User_2':0 },{ 'sHourName':'2am', 'User_1':0, 'User_2':0 },{ 'sHourName':'3am', 'User_1':0, 'User_2':0 },{ 'sHourName':'4am', 'User_1':0, 'User_2':0 },{ 'sHourName':'5am', 'User_1':0, 'User_2':0 },{ 'sHourName':'6am', 'User_1':0, 'User_2':0 },{ 'sHourName':'7am', 'User_1':0, 'User_2':1 },{ 'sHourName':'8am', 'User_1':0, 'User_2':99 },{ 'sHourName':'9am', 'User_1':0, 'User_2':28 },{ 'sHourName':'10am', 'User_1':0, 'User_2':28 },{ 'sHourName':'11am', 'User_1':0, 'User_2':153 },{ 'sHourName':'12pm', 'User_1':0, 'User_2':58 },{ 'sHourName':'1pm', 'User_1':0, 'User_2':42 },{ 'sHourName':'2pm', 'User_1':20, 'User_2':10 }] }); Ext.create('Ext.chart.Chart',{ id: 'RulesWrittenChart', renderTo: 'StatCharts_Display', width: iChartWidth, height: iChartHeight, animate: true, store: RulesCreatedStore, axes: [{ type: 'Numeric', position: 'left', fields: ['User_2','User_1'], title: 'Rules Written', grid: true },{ type: 'Category', position: 'bottom', fields: ['sHourName'], title: 'Hour', grid: false, label: { rotate: { degrees: 315 } } }], series: [{ type: 'line', axis: 'left', xField: 'sHourName', yField: 'User_2', highlight: { size: 3, radius: 3 } },{ type: 'line', axis: 'left', xField: 'sHourName', yField: 'User_1', highlight: { size: 3, radius: 3 } }] }); });

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  • ruby on rails one-to-many relationship

    - by fenec
    I would like to model a betting system relationship using the power of rails. so lets start with doing something very simple modelling the relationship from a user to a bet.i would like to have a model bet with 2 primary keys. here are my migrations enter code here class CreateBets < ActiveRecord::Migration def self.up create_table :bets do |t| t.integer :user_1_id t.integer :user_2_id t.integer :amount t.timestamps end end def self.down drop_table :bets end end class CreateUsers < ActiveRecord::Migration def self.up create_table :users do |t| t.string :name t.timestamps end end def self.down drop_table :users end end the models enter code here class Bet < ActiveRecord::Base belongs_to :user_1,:class_name=:User belongs_to :user_2,:class_name=:User end class User < ActiveRecord::Base has_many :bets, :foreign_key =:user_1) has_many :bets, :foreign_key =:user_2) end when i test here in the console my relationships I got an error enter code here u1=User.create :name="aa" = # u2=User.create :name="bb" = # b=Bet.create(:user_1=u1,:user_2=u2) *****error***** QUESTIONS: 1 How do I define the relationships between these tables correctly? 2 are there any conventions to name the attributes (ex:user_1_id...) thank you for your help

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  • Website does not automatically fit to iphone screen

    - by Ploetzeneder
    Hello, The following code does not fit onto the iphone screen; how do I have to define the viewport? <html> <body> <center> <div id="karteu" style="background: url('../customer/Karten/karte1.jpg') no-repeat left center;width:714px;height:540px;" > </div> </body> </html> Normally the site should be zoomed, so i first should see the website in small, and then be able to zoom that i see it in the original size, but in my case it does not, when i call the site, the zoom is, that the image has this original size already, and that i have to scroll, but i dont want to scroll,...i want to use the normal safari mobile zoom and then scroll The solution at the bottom does not zoom anything. I want to see the overview of the image at the beginning. Then i want to be able to zoom with the normal safari zoom functions,..

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  • Installing PIL on Cygwin

    - by Dustin
    I've been struggling all morning to get PIL installed on Cygwin. The errors I get are not consistent with common errors I find using Google. Perhaps a linux guru can see an obvious problem in this output: $ python setup.py install running install running build running build_py running build_ext building '_imaging' extension gcc -fno-strict-aliasing -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -DHAVE_LIBZ -I/usr/include/freetype2 -IlibImaging -I/usr/include -I/usr/include/python2.5 -c _imaging.c -o build/temp.cygwin-1.7.2-i686-2.5/_imaging.o In file included from /usr/lib/gcc/i686-pc-cygwin/3.4.4/include/syslimits.h:7, from /usr/lib/gcc/i686-pc-cygwin/3.4.4/include/limits.h:11, from /usr/include/python2.5/Python.h:18, from _imaging.c:75: /usr/lib/gcc/i686-pc-cygwin/3.4.4/include/limits.h:122:61: limits.h: No such file or directory In file included from _imaging.c:75: /usr/include/python2.5/Python.h:32:19: stdio.h: No such file or directory /usr/include/python2.5/Python.h:34:5: #error "Python.h requires that stdio.h define NULL." /usr/include/python2.5/Python.h:37:20: string.h: No such file or directory /usr/include/python2.5/Python.h:39:19: errno.h: No such file or directory /usr/include/python2.5/Python.h:41:20: stdlib.h: No such file or directory /usr/include/python2.5/Python.h:43:20: unistd.h: No such file or directory /usr/include/python2.5/Python.h:55:20: assert.h: No such file or directory In file included from /usr/include/python2.5/Python.h:57, from _imaging.c:75: /usr/include/python2.5/pyport.h:7:20: stdint.h: No such file or directory In file included from /usr/include/python2.5/Python.h:57, from _imaging.c:75: /usr/include/python2.5/pyport.h:89: error: parse error before "Py_uintptr_t" /usr/include/python2.5/pyport.h:89: warning: type defaults to `int' in declaration of `Py_uintptr_t' /usr/include/python2.5/pyport.h:89: warning: data definition has no type or storage class /usr/include/python2.5/pyport.h:90: error: parse error before "Py_intptr_t" /usr/include/python2.5/pyport.h:90: warning: type defaults to `int' in declaration of `Py_intptr_t' ... more lines like this

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  • Optimizing a shared buffer in a producer/consumer multithreaded environment

    - by Etan
    I have some project where I have a single producer thread which writes events into a buffer, and an additional single consumer thread which takes events from the buffer. My goal is to optimize this thing for a single machine to achieve maximum throughput. Currently, I am using some simple lock-free ring buffer (lock-free is possible since I have only one consumer and one producer thread and therefore the pointers are only updated by a single thread). #define BUF_SIZE 32768 struct buf_t { volatile int writepos; volatile void * buffer[BUF_SIZE]; volatile int readpos;) }; void produce (buf_t *b, void * e) { int next = (b->writepos+1) % BUF_SIZE; while (b->readpos == next); // queue is full. wait b->buffer[b->writepos] = e; b->writepos = next; } void * consume (buf_t *b) { while (b->readpos == b->writepos); // nothing to consume. wait int next = (b->readpos+1) % BUF_SIZE; void * res = b->buffer[b->readpos]; b->readpos = next; return res; } buf_t *alloc () { buf_t *b = (buf_t *)malloc(sizeof(buf_t)); b->writepos = 0; b->readpos = 0; return b; } However, this implementation is not yet fast enough and should be optimized further. I've tried with different BUF_SIZE values and got some speed-up. Additionaly, I've moved writepos before the buffer and readpos after the buffer to ensure that both variables are on different cache lines which resulted also in some speed. What I need is a speedup of about 400 %. Do you have any ideas how I could achieve this using things like padding etc?

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  • Django forms: how to dynamically create ModelChoiceField labels

    - by Henri
    I would like to create dynamic labels for a forms.ModelChoiceField and I'm wondering how to do that. I have the following form class: class ProfileForm(forms.ModelForm): def __init__(self, data=None, ..., language_code='en', family_name_label='Family name', horoscope_label='Horoscope type', *args, **kwargs): super(ProfileForm, self).__init__(data, *args, **kwargs) self.fields['family_name'].label = family_name_label . . self.fields['horoscope'].label = horoscope_label self.fields['horoscope'].queryset = Horoscope.objects.all() class Meta: model = Profile family_name = forms.CharField(widget=forms.TextInput(attrs={'size':'80', 'class': 'contact_form'})) . . horoscope = forms.ModelChoiceField(queryset = Horoscope.objects.none(), widget=forms.RadioSelect(), empty_label=None) The default labels are defined by the unicode function specified in the Profile definition. However the labels for the radio buttons created by the ModelChoiceField need to be created dynamically. First I thought I could simply override ModelChoiceField as described in the Django documentation. But that creates static labels. It allows you to define any label but once the choice is made, that choice is fixed. So I think I need to adapt add something to init like: class ProfileForm(forms.ModelForm): def __init__(self, data=None, ..., language_code='en', family_name_label='Family name', horoscope_label='Horoscope type', *args, **kwargs): super(ProfileForm, self).__init__(data, *args, **kwargs) self.fields['family_name'].label = family_name_label . . self.fields['horoscope'].label = horoscope_label self.fields['horoscope'].queryset = Horoscope.objects.all() self.fields['horoscope'].<WHAT>??? = ??? Anyone having any idea how to handle this? Any help would be appreciated very much.

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