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  • [C#] Improving method to read signed 8-bit integers from hexadecimal.

    - by JYelton
    Scenario: I have a string of hexadecimal characters which encode 8-bit signed integers. Each two characters represent a byte which employ the leftmost (MSB) bit as the sign (rather than two's complement). I am converting these to signed ints within a loop and wondered if there's a better way to do it. There are too many conversions and I am sure there's a more efficient method that I am missing. Current Code: string strData = "FFC000407F"; // example input data, encodes: -127, -64, 0, 64, 127 int v; for (int x = 0; x < strData.Length/2; x++) { v = HexToInt(strData.Substring(x * 2, 2)); Console.WriteLine(v); // do stuff with v } private int HexToInt(string _hexData) { string strBinary = Convert.ToString(Convert.ToInt32(_hexData, 16), 2).PadLeft(_hexData.Length * 4, '0'); int i = Convert.ToInt32(strBinary.Substring(1, 7), 2); i = (strBinary.Substring(0, 1) == "0" ? i : -i); return i; } Question: Is there a more streamlined and direct approach to reading two hex characters and converting them to an int when they represent a signed int (-127 to 127) using the leftmost bit as the sign?

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  • How to create static method that evaluates local static variable once?

    - by Viet
    I have a class with static method which has a local static variable. I want that variable to be computed/evaluated once (the 1st time I call the function) and for any subsequent invocation, it is not evaluated anymore. How to do that? Here's my class: template< typename T1 = int, unsigned N1 = 1, typename T2 = int, unsigned N2 = 0, typename T3 = int, unsigned N3 = 0, typename T4 = int, unsigned N4 = 0, typename T5 = int, unsigned N5 = 0, typename T6 = int, unsigned N6 = 0, typename T7 = int, unsigned N7 = 0, typename T8 = int, unsigned N8 = 0, typename T9 = int, unsigned N9 = 0, typename T10 = int, unsigned N10 = 0, typename T11 = int, unsigned N11 = 0, typename T12 = int, unsigned N12 = 0, typename T13 = int, unsigned N13 = 0, typename T14 = int, unsigned N14 = 0, typename T15 = int, unsigned N15 = 0, typename T16 = int, unsigned N16 = 0> struct GroupAlloc { static const uint32_t sizeClass; static uint32_t getSize() { static uint32_t totalSize = 0; totalSize += sizeof(T1)*N1; totalSize += sizeof(T2)*N2; totalSize += sizeof(T3)*N3; totalSize += sizeof(T4)*N4; totalSize += sizeof(T5)*N5; totalSize += sizeof(T6)*N6; totalSize += sizeof(T7)*N7; totalSize += sizeof(T8)*N8; totalSize += sizeof(T9)*N9; totalSize += sizeof(T10)*N10; totalSize += sizeof(T11)*N11; totalSize += sizeof(T12)*N12; totalSize += sizeof(T13)*N13; totalSize += sizeof(T14)*N14; totalSize += sizeof(T15)*N15; totalSize += sizeof(T16)*N16; totalSize = 8*((totalSize + 7)/8); return totalSize; } };

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  • Improving method to read signed 8-bit integers from hexadecimal.

    - by JYelton
    Scenario: I have a string of hexadecimal characters which encode 8-bit signed integers. Each two characters represent a byte which employ the leftmost (MSB) bit as the sign (rather than two's complement). I am converting these to signed ints within a loop and wondered if there's a better way to do it. There are too many conversions and I am sure there's a more efficient method that I am missing. Current Code: string strData = "FFC000407F"; // example input data, encodes: -127, -64, 0, 64, 127 int v; for (int x = 0; x < strData.Length/2; x++) { v = HexToInt(strData.Substring(x * 2, 2)); Console.WriteLine(v); // do stuff with v } private int HexToInt(string _hexData) { string strBinary = Convert.ToString(Convert.ToInt32(_hexData, 16), 2).PadLeft(_hexData.Length * 4, '0'); int i = Convert.ToInt32(strBinary.Substring(1, 7), 2); i = (strBinary.Substring(0, 1) == "0" ? i : -i); return i; } Question: Is there a more streamlined and direct approach to reading two hex characters and converting them to an int when they represent a signed int (-127 to 127) using the leftmost bit as the sign?

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  • PHP5 : Applying a method from an extended class on an object from the original (parent) class.

    - by Glauber Rocha
    Hello, I'm trying to extend two native PHP5 classes (DOMDocument and DOMNode) to implement 2 methods (selectNodes and selectSingleNode) in order to make XPath queries easier. I thought it would be rather straighforward, but I'm stuck in a problem which I think is an OOP beginner's issue. class nDOMDocument extends DOMDocument { public function selectNodes($xpath){ $oxpath = new DOMXPath($this); return $oxpath->query($xpath); } public function selectSingleNode($xpath){ return $this->selectNodes($xpath)->item(0); } } Then I tried to do extend DOMNode to implement the same methods so I can perform an XPath query directly on a node: class nDOMNode extends DOMNode { public function selectNodes($xpath){ $oxpath = new DOMXPath($this->ownerDocument,$this); return $oxpath->query($xpath); } public function selectSingleNode($xpath){ return $this->selectNodes($xpath)->item(0); } } Now if I execute the following code (on an arbitrary XMLDocument): $xmlDoc = new nDOMDocument; $xmlDoc->loadXML(...some XML...); $node1 = $xmlDoc->selectSingleNode("//item[@id=2]"); $node2 = $node1->selectSingleNode("firstname"); The third line works and returns a DOMNode object $node1. However, the fourth line doesn't work because the selectSingleNode method belongs to the nDOMNode class, not DOMNode. So my question: is there a way at some point to "transform" the returned DOMNode object into a nDOMNode object? I feel I'm missing some essential point here and I'd greatly appreciate your help. (Sorry, this is a restatement of my question http://stackoverflow.com/questions/2573820/)

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  • Why not lump all service classes into a Factory method (instead of injecting interfaces)?

    - by Andrew
    We are building an ASP.NET project, and encapsulating all of our business logic in service classes. Some is in the domain objects, but generally those are rather anemic (due to the ORM we are using, that won't change). To better enable unit testing, we define interfaces for each service and utilize D.I.. E.g. here are a couple of the interfaces: IEmployeeService IDepartmentService IOrderService ... All of the methods in these services are basically groups of tasks, and the classes contain no private member variables (other than references to the dependent services). Before we worried about Unit Testing, we'd just declare all these classes as static and have them call each other directly. Now we'll set up the class like this if the service depends on other services: public EmployeeService : IEmployeeService { private readonly IOrderService _orderSvc; private readonly IDepartmentService _deptSvc; private readonly IEmployeeRepository _empRep; public EmployeeService(IOrderService orderSvc , IDepartmentService deptSvc , IEmployeeRepository empRep) { _orderSvc = orderSvc; _deptSvc = deptSvc; _empRep = empRep; } //methods down here } This really isn't usually a problem, but I wonder why not set up a factory class that we pass around instead? i.e. public ServiceFactory { virtual IEmployeeService GetEmployeeService(); virtual IDepartmentService GetDepartmentService(); virtual IOrderService GetOrderService(); } Then instead of calling: _orderSvc.CalcOrderTotal(orderId) we'd call _svcFactory.GetOrderService.CalcOrderTotal(orderid) What's the downfall of this method? It's still testable, it still allows us to use D.I. (and handle external dependencies like database contexts and e-mail senders via D.I. within and outside the factory), and it eliminates a lot of D.I. setup and consolidates dependencies more. Thanks for your thoughts!

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  • How to pass a value from a method to property procedure in c#?

    - by sameer
    Here is my code: The jewellery class is my main class in which i am inheriting a connection string class. class Jewellery : Connectionstr { string lmcode; public string LM_code/**/Here i want to access the value of the method ReadData i.e displaystring and i want to store this value in the insert query below.** { get { return lmcode; } set { lmcode = value; } } string mname; public string M_Name { get { return mname; } set { mname = value; } } string desc; public string Desc { get { return desc; } set { desc = value; } } public string ReadData() { OleDbDataReader dr; string jid = string.Empty; string displayString = string.Empty; String query = "select max(LM_code)from Master_Accounts"; Datamanager.RunExecuteReader(Constr, query); if (dr.Read()) { jid = dr[0].ToString(); if (string.IsNullOrEmpty(jid)) { jid = "AM0000"; } int len = jid.Length; string split = jid.Substring(2, len - 2); int num = Convert.ToInt32(split); num++; displayString = jid.Substring(0, 2) + num.ToString("0000"); dr.Close(); } **return displayString;** I want to pass this value to the above property procedure above i.e LM_code. } public void add() { String query ="insert into Master_Accounts values ('" + LM_code + "','" + M_Name + "'," + "'" + Desc + "')"; Datamanager.RunExecuteNonQuery(Constr , query);// } If possible can u edit this code! Anticipated thanks by sameer

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  • The dealloc method is not called in the present modal view contrller.

    - by Madan Mohan
    It is in My view controller -(void)doctorsListAction { if(isFirst == YES) { [self getDoctorsListController]; [[self navigationController] presentModalViewController:doctorListViewNavigationController animated:YES]; [doctorListViewController release]; } } -(void)getDoctorsListController { //DoctorListViewController *doctorListViewController=[[[DoctorListViewController alloc]initWithNibName:nil bundle:nil]autorelease]; doctorListViewController=[[DoctorListViewController alloc]init]; doctorListViewNavigationController=[[UINavigationController alloc]initWithRootViewController:doctorListViewController]; doctorListViewController.doctorList=doctorList; doctorListViewNavigationController.navigationBar.barStyle= UIBarStyleBlackOpaque; [doctorListViewController release]; } It is in DoctorListViewContrller -(void)closeAction { printf("\n hai i am in close action*******************************"); //[doctorList release]; //[myTableView release]; //myTableView=nil; printf("\n myTableView retainCount :%d",[myTableView retainCount]); [[self navigationController] dismissModalViewControllerAnimated:YES]; } //this method is not called I don't know why if it not called i will get memory issues - (void)dealloc { printf("\n hai i am in dealloc of Doctor list view contrller"); [doctorList release]; [myTableView release]; myTableView=nil; [super dealloc]; }

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  • How to test if raising an event results in a method being called conditional on value of parameters

    - by MattC
    I'm trying to write a unit test that will raise an event on a mock object which my test class is bound to. What I'm keen to test though is that when my test class gets it's eventhandler called it should only call a method on certain values of the eventhandlers parameters. My test seems to pass even if I comment the code that calls ProcessPriceUpdate(price); I'm in VS2005 so no lambdas please :( So... public delegate void PriceUpdateEventHandler(decimal price); public interface IPriceInterface{ event PriceUpdateEventHandler PriceUpdate; } public class TestClass { IPriceInterface priceInterface = null; TestClass(IPriceInterface priceInterface) { this.priceInterface = priceInterface; } public void Init() { priceInterface.PriceUpdate += OnPriceUpdate; } public void OnPriceUpdate(decimal price) { if(price > 0) ProcessPriceUpdate(price); } public void ProcessPriceUpdate(decimal price) { //do something with price } } And my test so far :s public void PriceUpdateEvent() { MockRepository mock = new MockRepository(); IPriceInterface pi = mock.DynamicMock<IPriceInterface>(); TestClass test = new TestClass(pi); decimal prc = 1M; IEventRaiser raiser; using (mock.Record()) { pi.PriceUpdate += null; raiser = LastCall.IgnoreArguments().GetEventRaiser(); Expect.Call(delegate { test.ProcessPriceUpdate(prc); }).Repeat.Once(); } using (mock.Playback()) { test.Init(); raiser.Raise(prc); } }

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  • Why this method does not use any properties of the object?

    - by Roman
    Here I found this code: import java.awt.*; import javax.swing.*; public class FunWithPanels extends JFrame { public static void main(String[] args) { FunWithPanels frame = new FunWithPanels(); frame.doSomething(); } void doSomething() { Container c = getContentPane(); JPanel p1 = new JPanel(); p1.setLayout(new BorderLayout()); p1.add(new JButton("A"), BorderLayout.NORTH); p1.add(new JButton("B"), BorderLayout.WEST); JPanel p2 = new JPanel(); p2.setLayout(new GridLayout(3, 2)); p2.add(new JButton("F")); p2.add(new JButton("G")); p2.add(new JButton("H")); p2.add(new JButton("I")); p2.add(new JButton("J")); p2.add(new JButton("K")); JPanel p3 = new JPanel(); p3.setLayout(new BoxLayout(p3, BoxLayout.Y_AXIS)); p3.add(new JButton("L")); p3.add(new JButton("M")); p3.add(new JButton("N")); p3.add(new JButton("O")); p3.add(new JButton("P")); c.setLayout(new BorderLayout()); c.add(p1, BorderLayout.CENTER); c.add(p2, BorderLayout.SOUTH); c.add(p3, BorderLayout.EAST); pack(); setVisible(true); } } I do not understand how "doSomething" use the fact that "frame" is an instance of the class JFrame. It is not clear to me because there is no reference to "this" in the code for the method "doSomething".

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  • Does isEmpty method in Stream evaluate the whole Stream?

    - by abhin4v
    In Scala, does calling isEmtpy method on an instance of Stream class cause the stream to be evaluated completely? My code is like this: import Stream.cons private val odds: Stream[Int] = cons(3, odds.map(_ + 2)) private val primes: Stream[Int] = cons(2, odds filter isPrime) private def isPrime(n: Int): Boolean = n match { case 1 => false case 2 => true case 3 => true case 5 => true case 7 => true case x if n % 3 == 0 => false case x if n % 5 == 0 => false case x if n % 7 == 0 => false case x if (x + 1) % 6 == 0 || (x - 1) % 6 == 0 => true case x => primeDivisors(x) isEmpty } import Math.{sqrt, ceil} private def primeDivisors(n: Int) = primes takeWhile { _ <= ceil(sqrt(n))} filter {n % _ == 0 } So, does the call to isEmpty on the line case x => primeDivisors(x) isEmpty cause all the prime divisors to be evaluated or only the first one?

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  • Raising C# events with an extension method - is it bad?

    - by Kyralessa
    We're all familiar with the horror that is C# event declaration. To ensure thread-safety, the standard is to write something like this: public event EventHandler SomethingHappened; protected virtual void OnSomethingHappened(EventArgs e) { var handler = SomethingHappened; if (handler != null) handler(this, e); } Recently in some other question on this board (which I can't find now), someone pointed out that extension methods could be used nicely in this scenario. Here's one way to do it: static public class EventExtensions { static public void RaiseEvent(this EventHandler @event, object sender, EventArgs e) { var handler = @event; if (handler != null) handler(sender, e); } static public void RaiseEvent<T>(this EventHandler<T> @event, object sender, T e) where T : EventArgs { var handler = @event; if (handler != null) handler(sender, e); } } With these extension methods in place, all you need to declare and raise an event is something like this: public event EventHandler SomethingHappened; void SomeMethod() { this.SomethingHappened.RaiseEvent(this, EventArgs.Empty); } My question: Is this a good idea? Are we missing anything by not having the standard On method? (One thing I notice is that it doesn't work with events that have explicit add/remove code.)

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  • Why Can I Change Struct's int[] Property from Method Without Specifying "ref"?

    - by AMissico
    From a method, I can pass a struct which contains an array of integers, and change the values in the array. I am not sure I understand fully why I can do this. Can someone please explain why I can change the values stored in the int[]? private void DoIt(){ SearchInfo a = new SearchInfo(); a.Index = 1; a.Map = new int[] { 1 }; SearchInfo b = new SearchInfo(); b.Index = 1; b.Map = new int[] { 1 }; ModifyA(a); ModifyB(ref b); Debug.Assert(a.Index == 1); Debug.Assert(a.Map[0] == 1, "why did this change?"); Debug.Assert(b.Index == 99); Debug.Assert(b.Map[0] == 99); } void ModifyA(SearchInfo a) { a.Index = 99; a.Map[0] = 99; } void ModifyB(ref SearchInfo b) { b.Index = 99; b.Map[0] = 99; } struct SearchInfo { public int[] Map; public int Index; }

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  • Undefined method `add' on a cucumber step that usually works.

    - by Josiah Kiehl
    I have a path defined: when /the admin home\s?page/ "/admin/" I have scenario that is passing: Scenario: Let admins see the admin homepage Given "pojo" is logged in And "pojo" is an "admin" And I am on the admin home page Then I should see "Hi there." And I have a scenario that is failing: Scenario: Review flagged photo Given "pojo" is logged in And "pojo" is an "admin" ...bunch of steps that create stuff in the database... And I am on the admin home page Then ... the rest of the steps The step that fails in the second one is "And I am on the admin home page" which passes just fine in the first scenario. Here's the error I get: And I am on the admin home page # features/step_definitions/web_steps.rb:18 undefined method `add' for {}:Hash (NoMethodError) ./app/controllers/admin_controller.rb:13:in `index' ./app/controllers/admin_controller.rb:11:in `each' ./app/controllers/admin_controller.rb:11:in `index' /usr/lib/ruby/1.8/benchmark.rb:308:in `realtime' ./features/step_definitions/web_steps.rb:19:in `/^(?:|I )am on (.+)$/' features/admin.feature:52:in `And I am on the admin home page' This is very odd... why would it be fine in the first case, and not in the second where the only difference are a bunch of steps that create records in the db? [edit] Here's the add stuff to database step: Given /^there is a "([^\"]*)" with the following:$/ do |model, table| model.constantize.create!(table.rows_hash) end

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  • Why is there a constructor method if you can assign the values to variables?

    - by Joel
    I'm just learning PHP, and I'm confused about what the purpose of the __construct() method? If I can do this: class Bear { // define properties public $name = 'Bill'; public $weight = 200; // define methods public function eat($units) { echo $this->name." is eating ".$units." units of food... <br />"; $this->weight += $units; } } Then why do it with a constructor instead? : class Bear { // define properties public $name; public $weight; public function __construct(){ $this->name = 'Bill'; $this->weight = 200; } // define methods public function eat($units) { echo $this->name." is eating ".$units." units of food... <br />"; $this->weight += $units; } }

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  • Would this method work to scale out SQL queries?

    - by David
    I have a database containing a single huge table. At the moment a query can take anything from 10 to 20 minutes and I need that to go down to 10 seconds. I have spent months trying different products like GridSQL. GridSQL works fine, but is using its own parser which does not have all the needed features. I have also optimized my database in various ways without getting the speedup I need. I have a theory on how one could scale out queries, meaning that I utilize several nodes to run a single query in parallel. The idea is to take an incoming SQL query and simply run it exactly like it is on all the nodes. When the results are returned to a coordinator node, the same query is run on the union of the resultsets. I realize that an aggregate function like average need to be rewritten into a count and sum to the nodes and that the coordinator divides the sum of the sums with the sum of the counts to get the average. What kinds of problems could not easily be solved using this model. I believe one issue would be the count distinct function. Edit: I am getting so many nice suggestions, but none have addressed the method.

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  • accessing a method from a button within a class?

    - by flo
    #import "GameObject.h" #import "Definitions.h" @implementation GameObject @synthesize owner; @synthesize state; @synthesize mirrored; @synthesize button; @synthesize switcher; - (id) init { if ( self = [super init] ) { [self setOwner: EmptyField]; button = [UIButton buttonWithType:UIButtonTypeCustom]; [self setSwitcher: FALSE]; } return self; } - (UIButton*) display{ button.frame = CGRectMake(0, 0, GO_Width, GO_Height); [button setBackgroundImage:[UIImage imageNamed:BlueStone] forState:UIControlStateNormal]; [button addTarget:self action:@selector(buttonPressed:) forControlEvents:UIControlEventTouchUpInside]; return button; } -(void)buttonPressed:(id) sender { //... } } - (void) dealloc { [super dealloc]; } @end Hi! i would like to know if the above is possible somehow within a class (in my case it is called GameObject) or if i HAVE to have the button call a methode in the viewcontroller... the above results with the app crashing. i would call display within a loop on the viewcontroller and id like to change some of the GameObjects instance variables within buttonPressed. Also id like to change some other stuff by calling some other methods from within buttonPressed but i think that will be the lesser of my problems ;) also id like to know how i can pass some variables to the buttonPressed method... cant find it anywhere :( help on this one would be much appreciated ;) thanks flo

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  • Should a Trim method generally in the Data Access Layer or with in the Domain Layer?

    - by jpierson
    I'm dealing with a database that contains data with inconsistencies such as white leading and trailing white space. In general I see a lot of developers practice defensive coding by trimming almost all strings that come from the database that may have been entered by a user at some point. In my oppinoin it is better to do such formating before data is persisted so that it is done only once and then the data can be in a consistent and reliable state. Unfortunatley this is not the case however which leads me to the next best solution, using a Trim method. If I trim all data as part of my data access layer then I don't have to concern myself with defensive trimming within the business objects of my domain layer. If I instead put the trimming responsibility in my business objects, such as with set accessors of my C# properties, I should get the same net results however the trim will be operating on all values assigned to my business objects properties not just the ones that come from the inconsistent database. I guess as a somewhat philisophical question that may determine the answer I could ask "Should the domain later be responsible for defensive/coercive formatting of data?" Would it make sense to have a set accessor for a PhoneNumber property on a business object accept a unformatted or formatted string and then attempt to format it as required or should this responsibility be pushed to the presentation and data access layers leaving the domain layer more strict in the type of data that it will accept? I think this may be the more fundamental question. Update: Below are a few links that I thought I should share about the topic of data cleansing. Information service patterns, Part 3: Data cleansing pattern LINQ to SQL - Format a string before saving? How to trim values using Linq to Sql?

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  • certain BitMapData types dont work in a beginBitmapFill() method.

    - by numerical25
    Say I loaded a bitMap into a bitmapData type called tileImage. tileImage = Bitmap(loader.content).bitmapData; say I decided to add that bitmap into a sprite like below this.graphics.beginBitmapFill(tileImage ); this.graphics.drawRect(0, 0,tWidth ,tHeight ); It would of course work. But say If I decided to add tileImage into a another bitMapData type like below var tImage:BitmapData = new BitmapData(30,30); tImage.copyPixels(tileImage,tRect,tPoint); and I then added tImage to my sprite this.graphics.beginBitmapFill(tImage); this.graphics.drawRect(0, 0,tWidth ,tHeight ); I then get the following error ArgumentError: Error #2015: Invalid BitmapData. tRect and tPoint are all predefined and set. tRect x and y are 0,0 and the width and height are 30x30. tPoint is 0,0 as well. Yes I understand that this is a very brief explanation but I wanted to elaborate that a bitMapdata type that has its data from the copypixel method does not work with beginBitmapFill. but a varible that gets its data straigt from the source, does. One works, and one doesnt, yet they are both the same data types. why is this ?

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  • Why can't I pass self as a named argument to an instance method in Python?

    - by Joseph Garvin
    This works: >>> def bar(x, y): ... print x, y ... >>> bar(y=3, x=1) 1 3 And this works: >>> class foo(object): ... def bar(self, x, y): ... print x, y ... >>> z = foo() >>> z.bar(y=3, x=1) 1 3 And even this works: >>> foo.bar(z, y=3, x=1) 1 3 But why doesn't this work? >>> foo.bar(self=z, y=3, x=1) Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: unbound method bar() must be called with foo instance as first argument (got nothing instead) This makes metaprogramming more difficult, because it requires special case handling. I'm curious if it's somehow necessary by Python's semantics or just an artifact of implementation.

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  • Method works on Emulator but no on Microsoft Surface unit?

    - by Roflcoptr
    I have the following code. The StartRecord method trows an error on the Microsoft Surface Unit. But when I'm testing it on the emulator, it all works great. Any hints how 1) to find the exception that is thrown on the Microsoft Surface Unit? 2) to find the error in the code? any assumptions? private void StartRecord(object sender, ContactEventArgs e) { isRecording = true; StartButton.IsEnabled = false; recordTimer = new Timer(10); recordTimer.Elapsed += new ElapsedEventHandler(recordTimer_Elapsed); PlaybackRoot.Visibility = System.Windows.Visibility.Collapsed; EllapsedRecord.Visibility = System.Windows.Visibility.Visible; InputLevel.Visibility = System.Windows.Visibility.Visible; long time = DateTime.Now.Ticks; String fileName = Convert.ToString(time) + ".wav"; Console.WriteLine(fileName); startTime = DateTime.UtcNow; recordTimer.Start(); record = new AudioRecording(fileName); record.getSampleAggregator().MaximumCalculated += new EventHandler<MaxSampleEventArgs>(AudioControl_MaximumCalculated); record.start(); }

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  • Does The Clear Method On A Collection Release The Event Subscriptions?

    - by DaveB
    I have a collection private ObservableCollection<Contact> _contacts; In the constructor of my class I create it _contacts = new ObservableCollection<Contact>(); I have methods to add and remove items from my collection. I want to track changes to the entities in my collection which implement the IPropertyChanged interface so I subscribe to their PropertyChanged event. public void AddContact(Contact contact) { ((INotifyPropertyChanged)contact).PropertyChanged += new PropertyChangedEventHandler(Contact_PropertyChanged); _contacts.Add(contact); } public void AddContact(int index, Contact contact) { ((INotifyPropertyChanged)contact).PropertyChanged += new PropertyChangedEventHandler(Contact_PropertyChanged); _contacts.Insert(index, contact); } When I remove an entity from the collection, I unsubscribe from the PropertyChanged event. I am told this is to allow the entity to be garbage collected and not create memory issues. public void RemoveContact(Contact contact) { ((INotifyPropertyChanged)contact).PropertyChanged -= Contact_PropertyChanged; _contacts.Remove(contact); } So, I hope this is all good. Now, I need to clear the collection in one of my methods. My first thought would be to call _contacts.Clear(). Then I got to wondering if this releases those event subscriptions? Would I need to create my own clear method? Something like this: public void ClearContacts() { foreach(Contact contact in _contacts) { this.RemoveContact(contact); } } I am hoping one of the .NET C# experts here could clear this up for me or tell me what I am doing wrong.

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  • Error: "an object reference is required for the non-static field, method or property..."

    - by user300484
    Hi! Im creating an application on C#. Its function is to evualuate if a given is prime and if the same swapped number is prime as well. When I build my solution on Visual Studio, it says that "an object reference is required for the non-static field, method or property...". Im having this problem with the "volteado" and "siprimo" methods. Can you tell me where is the problem and how i can fix it? thank you! namespace ConsoleApplication1 { class Program { static void Main(string[] args) { Console.Write("Write a number: "); long a= Convert.ToInt64(Console.ReadLine()); // a is the number given by the user long av = volteado(a); // av is "a" but swapped if (siprimo(a) == false && siprimo(av) == false) Console.WriteLine("Both original and swapped numbers are prime."); else Console.WriteLine("One of the numbers isnt prime."); Console.ReadLine(); } private bool siprimo(long a) {// evaluate if the received number is prime bool sp = true; for (long k = 2; k <= a / 2; k++) if (a % k == 0) sp = false; return sp; } private long volteado(long a) {// swap the received number long v = 0; while (a > 0) { v = 10 * v + a % 10; a /= 10; } return v; } } }

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  • How to patch an S4 method in an R package?

    - by Richie Cotton
    If you find a bug in a package, it's usually possible to patch the problem with fixInNamespace, e.g. fixInNamespace("mean.default", "base"). For S4 methods, I'm not sure how to do it though. The method I'm looking at is in the gWidgetstcltk package. You can see the source code with getMethod(".svalue", c("gTabletcltk", "guiWidgetsToolkittcltk")) I can't find the methods with fixInNamespace. fixInNamespace(".svalue", "gWidgetstcltk") Error in get(subx, envir = ns, inherits = FALSE) : object '.svalue' not found I thought setMethod might do the trick, but setMethod(".svalue", c("gTabletcltk", "guiWidgetsToolkittcltk"), definition = function (obj, toolkit, index = NULL, drop = NULL, ...) { widget = getWidget(obj) sel <- unlist(strsplit(tclvalue(tcl(widget, "selection")), " ")) if (length(sel) == 0) { return(NA) } theChildren <- .allChildren(widget) indices <- sapply(sel, function(i) match(i, theChildren)) inds <- which(visible(obj))[indices] if (!is.null(index) && index == TRUE) { return(inds) } if (missing(drop) || is.null(drop)) drop = TRUE chosencol <- tag(obj, "chosencol") if (drop) return(obj[inds, chosencol, drop = drop]) else return(obj[inds, ]) }, where = "package:gWidgetstcltk" ) Error in setMethod(".svalue", c("gTabletcltk", "guiWidgetsToolkittcltk"), : the environment "gWidgetstcltk" is locked; cannot assign methods for function ".svalue" Any ideas?

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  • Use PermGen space or roll-my-own intern method?

    - by Adamski
    I am writing a Codec to process messages sent over TCP using a bespoke wire protocol. During the decode process I create a number of Strings, BigDecimals and dates. The client-server access patterns mean that it is common for the client to issue a request and then decode thousands of response messages, which results in a large number of duplicate Strings, BigDecimals, etc. Therefore I have created an InternPool<T> class allowing me to intern each class of object. Internally, the pool uses a WeakHashMap<T, WeakReferemce<T>>. For example: InternPool<BigDecimal> pool = new InternPool<BigDecimal>(); ... // Read BigDecimal from in buffer and then intern. BigDecimal quantity = pool.intern(readBigDecimal(in)); My question: I am using InternPool for BigDecimal but should I consider also using it for String instead of String's intern() method, which I believe uses PermGen space? What is the advantage of using PermGen space?

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  • what use does the javascript forEach method have (that map can't do)?

    - by JohnMerlino
    Hey all, The only difference I see in map and foreach is that map is returning an array and foreach is not. However, I don't even understand the last line of the foreach method "func.call(scope, this[i], i, this);". For example, isn't "this" and "scope" referring to same object and isn't this[i] and i referring to the current value in the loop? I noticed on another post someone said "Use forEach when you want to do something on the basis of each element of the list. You might be adding things to the page, for example. Essentially, it's great for when you want "side effects". I don't know what is meant by side effects. Array.prototype.map = function(fnc) { var a = new Array(this.length); for (var i = 0; i < this.length; i++) { a[i] = fnc(this[i]); } return a; } Array.prototype.forEach = function(func, scope) { scope = scope || this; for (var i = 0, l = this.length; i < l; i++) func.call(scope, this[i], i, this); } Finally, are there any real uses for these methods in javascript (since we aren't updating a database) other than to manipulate numbers like this: alert([1,2,3,4].map(function(x){ return x + 1})); //this is the only example I ever see of map in javascript. Thanks for any reply.

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