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  • Why doesn't is operator take in consideration if the explicit operator is overriden when checking ty

    - by Galilyou
    Hey Guys, Consider this code sample: public class Human { public string Value { get; set;} } public class Car { public static explicit operator Human (Car c) { Human h = new Human(); h.Value = "Value from Car"; return h; } } public class Program { public static void Mani() { Car c = new Car(); Human h = (Human)c; Console.WriteLine("h.Value = {0}", h.Value); Console.WriteLine(c is Human); } } Up I provide a possibility of an explicit cast from Car to Human, though Car and Human hierarchically are not related! The above code simply means that "Car is convertible to human" However, if you run the snippet you will find the expression c is Human evaluates to false! I used to believe that the is operator is kinda expensive cause it attempts to do an actual cast that might result in an InvalidCastException. If the operator is trying to cast, then the cast should succeed as there's an operator logic that should perform the cast! What does "is" test? Does test a hierarchical "is-a" relationship? Does test whether a variable type is convertible to a type?

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  • How can I create Wikipedia's footnote highlighting solely with jQuery

    - by andrew.bachman
    I would like to duplicate Wikipedia's footnote highlighting from in-text citation click solely in jQuery and CSS classes. I found a webpage that describes how to do so with CSS3 and then a JavaScript solution for IE. I would like however to do so solely with jQuery as the site I'm doing it on already has a bunch of jQuery elements. I've come up with a list of the process. In-Text Citation Clicked Replace highlight class with standard footnote class on <p> tag of footnotes that are already highlighted. Add highlight to the appropriate footnote Use jQuery to scroll down the page to appropriate footnote. I've come up with some jQuery so far but I'm extremely new to it relying heavy on tutorials and plugins to this point. Here is what I have with some plain English for the parts I haven't figured out yet. $('.inlineCite').click(function() { $('.footnoteHighlight').removeClass('footnoteHighlight').addClass('footnote'); //add highlight to id of highlightScroll //scroll to footnote with matching id }); If I had a method to pass a part of the selector into the function and turn it into a variable I believe I could pull it off. Most likely I'm sure one of you gurus will whip something up that puts anything I think I have done to shame. Any help will be greatly appreciated so thank you in advance. Cheers.

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  • Applying policy based design question

    - by Arthur
    I've not read the Modern C++ Design book but have found the idea of behavior injection through templates interesting. I am now trying to apply it myself. I have a class that has a logger that I thought could be injected as a policy. The logger has a log() method which takes an std::string or std::wstring depending on its policy: // basic_logger.hpp template<class String> class basic_logger { public: typedef String string_type; void log(const string_type & s) { ... } }; typedef basic_logger<std::string> logger; typedef basic_logger<std::wstring> wlogger; // reader.hpp template<class Logger = logger> class reader { public: typedef Logger logger_type; void read() { _logger.log("Reading..."); } private: logger_type _logger; }; Now the questing is, should the reader take a Logger as an argument, like above, or should it take a String and then instantiate a basic_logger as an instance variable? Like so: template<class String> class reader { public: typedef String string_type; typedef basic_logger<string_type> logger_type; // ... private: logger_type _logger; }; What is the right way to go?

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  • Generic Singleton Façade design pattern

    - by Paul
    Hi I try write singleton façade pattern with generics. I have one problem, how can I call method from generic variable. Something like this: T1 t1 = new T1(); //call method from t1 t1.Method(); In method SingletonFasadeMethod I have compile error: Error 1 'T1' does not contain a definition for 'Method' and no extension method 'Method' accepting a first argument of type 'T1' could be found (are you missing a using directive or an assembly reference?) Any advace? Thank, I am beginner in C#. All code is here: namespace GenericSingletonFasade { public interface IMyInterface { string Method(); } internal class ClassA : IMyInterface { public string Method() { return " Calling MethodA "; } } internal class ClassB : IMyInterface { public string Method() { return " Calling MethodB "; } } internal class ClassC : IMyInterface { public string Method() { return "Calling MethodC"; } } internal class ClassD : IMyInterface { public string Method() { return "Calling MethodD"; } } public class SingletonFasade<T1,T2,T3> where T1 : class,new() where T2 : class,new() where T3 : class,new() { private static T1 t1; private static T2 t2; private static T3 t3; private SingletonFasade() { t1 = new T1(); t2 = new T2(); t3 = new T3(); } class SingletonCreator { static SingletonCreator() { } internal static readonly SingletonFasade<T1,T2,T3> uniqueInstace = new SingletonFasade<T1,T2,T3>(); } public static SingletonFasade<T1,T2,T3> UniqueInstace { get { return SingletonCreator.uniqueInstace; } } public string SingletonFasadeMethod() { //Problem is here return t1.Method() + t2.Method() + t3.Method(); } } } I use this for my problem. public class SingletonFasade<T1, T2, T3> where T1 : class, IMyInterface, new() where T2 : class, IMyInterface, new() where T3 : class, IMyInterface, new() {//...} Is any solution without Interfaces ??

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  • Read XML with PHP

    - by sea_1987
    I am trying to check a field in some XML that is returned from an outside. The XML is returned in a variable call $out and when you view the source of the page you get a XML output of the following, <?xml version="1.0" encoding="UTF-8"?> <ResponseBlock Live="FALSE" Version="3.51"> <Response Type="AUTH"> <OperationResponse> <TransactionReference>23-9-1334895</TransactionReference> <TransactionCompletedTimestamp>2010-04-30 15:59:05</TransactionCompletedTimestamp> <AuthCode>AUTH CODE:TEST</AuthCode> <TransactionVerifier>AlaUOS1MOnN/iwc5s2WPDm5ggrCLwesUnHs9h+W0N3CRaln2W6lh+6dtaRFFhLdwfnw6y7lRemyJUYl9a3dpWfzORE6DaZkFMb+dIb0Ne1UxjFEJkrEtjzx/i8KSayrIBrT/yGZOoOT42EZ9loc+UkdGk/pqYvj8bZztvgBNo2Ak=</TransactionVerifier> <Result>1</Result> <SettleStatus>0</SettleStatus> <SecurityResponseSecurityCode>1</SecurityResponseSecurityCode> <SecurityResponsePostCode>1</SecurityResponsePostCode> <SecurityResponseAddress>1</SecurityResponseAddress> </OperationResponse> <Order> <OrderInformation>This is a test order</OrderInformation> <OrderReference>Order0001</OrderReference> </Order> </Response> </ResponseBlock> I want check what value is in the 'Result' field. I am unsure how to access the information using PHP, so far I have, $xml = simplexml_load_string($out); Many Thanks

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  • clojure: ExceptionInInitializerError in Namespace.<init> loading from a non-default classpath

    - by Charles Duffy
    In attempting to load an AOT-compiled class from a non-default classpath, I receive the following exception: Traceback (innermost last): File "test.jy", line 10, in ? at clojure.lang.Namespace.<init>(Namespace.java:34) at clojure.lang.Namespace.findOrCreate(Namespace.java:176) at clojure.lang.Var.internPrivate(Var.java:149) at aot_demo.JavaClass.<clinit>(Unknown Source) at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Class.java:247) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) java.lang.ExceptionInInitializerError: java.lang.ExceptionInInitializerError I'm able to reproduce this with the following trivial project.clj: (defproject aot-demo "0.1.0-SNAPSHOT" :dependencies [[org.clojure/clojure "1.3.0"]] :aot [aot-demo.core]) ...and src/aot_demo/core.clj defined as follows: (ns aot-demo.core (:gen-class :name aot_demo.JavaClass :methods [#^{:static true} [lower [java.lang.String] java.lang.String]])) (defn -lower [str] (.toLower str)) The following Jython script is then sufficient to trigger the bug: #!/usr/bin/jython import java.lang.Class import java.net.URLClassLoader import java.net.URL import os cl = java.net.URLClassLoader( [java.net.URL('file://%s/target/aot-demo-0.1.0-SNAPSHOT-standalone.jar' % (os.getcwd()))]) java.lang.Class.forName('aot_demo.JavaClass', True, cl) However, the exception does not occur if the test script is started with the uberjar already in the CLASSPATH variable. What's going on here? I'm trying to write a plugin for the BaseX database in Clojure; the above accurately represents how their plugin-loading mechanism works for the purpose of providing a SSCE for this problem.

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  • multi-dimension array value sorting in php

    - by David
    Another potentially interesting (or n00b, whatever comes first) question. I am building up an array with a set of database fields with information about table, actual field name and descriptive field name as a multi-dimensional array. Here is what it currently looks like: $Fields['User']['ID'] = "User ID"; $Fields['User']['FirstName'] = "First Name"; $Fields['Stats']['FavouriteOrder'] = "Favourite Item Ordered"; $Fields['Geographic']['Location'] = "Current Location"; $Fields['Geographic']['LocationCode'] = "Current Location Code"; Okay, this is fine, but I am piping this into a system that allows exporting of selected fields, and in the end I want to foreach() through the different levels, extract the data and then ultimately have all the descriptive fields to be displayed sorted alphabetically using their descriptive name. So ultimately in the order: Current Location, Current Location Code, Favourite Item Ordered, First Name then User ID - obviously keeping index associations. I can't use usort() and I can't use array_multisort()... or maybe I can and I just don't know how. usort() seems to need a key to sort by, but I have variable keys. array_multisort() just seems to do the same as sort() really. Any ideas?

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  • javascript plugin - singleton pattern?

    - by Adam Kiss
    intro Hello, I'm trying to develop some plugin or/*and* object in javascript, which will control some properties over some object. It will also use jQuery, to ease development. idea This is in pseudocode to give you an idea, since I can't really describe it in english with the right words, it's impossible to go and use google to find out what I want to use (and learn). I will have plugin (maybe object?) with some variables and methods: plugin hideshow(startupconfig){ var c, //collection add: function(what){ c += what; }, do: function(){ c.show().hide().stop(); //example code } } and I will use it this way (or sort-of): var p = new Plugin(); p .add($('p#simple')) .add($('p#simple2')) .do(); note I'm not really looking for jQuery plugin tutorials - it's more like usage of singleton pattern in document in javascript, jQuery is mentione only because it will be used to modify dom and simplify selectors, jQuery plugin maybe just for that one little function add. I'm looking for something, that will sit on top of my document and call functions from itselft based on timer, or user actions, or whatever. problems I don't really know where to start with construction of this object/plugin I'm not really sure how to maintain one variable, which is collection of jQuery objects (something like $('#simple, #simple2');) I would maybe like to extedn jQuery with $.fn.addToPlugin to use chaining of objects, but that should be simple (really just each( p.add($(this)); )) I hope I make any sense, ideas, links or advices appreciated.

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  • class header+ implementation

    - by igor
    what am I doing wrong here? I keep on getting a compilation error when I try to run this in codelab (turings craft) Instructions: Write the implementation (.cpp file) of the GasTank class of the previous exercise. The full specification of the class is: A data member named amount of type double. A constructor that no parameters. The constructor initializes the data member amount to 0. A function named addGas that accepts a parameter of type double . The value of the amount instance variable is increased by the value of the parameter. A function named useGas that accepts a parameter of type double . The value of the amount data member is decreased by the value of the parameter. A function named getGasLevel that accepts no parameters. getGasLevel returns the value of the amount data member. class GasTank{ double amount; GasTank(); void addGas(double); void useGas(double); double getGasLevel();}; GasTank::GasTank(){ amount=0;} double GasTank::addGas(double a){ amount+=a;} double GasTank::useGas(double a){ amount+=a;} double GasTank::getGasLevel(){ return amount;}

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  • Confused as to use a class or a function: Writing XML files using lxml and Python

    - by PulpFiction
    Hi. I need to write XML files using lxml and Python. However, I can't figure out whether to use a class to do this or a function. The point being, this is the first time I am developing a proper software and deciding where and why to use a class still seems mysterious. I will illustrate my point. For example, consider the following function based code I wrote for adding a subelement to a etree root. from lxml import etree root = etree.Element('document') def createSubElement(text, tagText = ""): etree.SubElement(root, text) # How do I do this: element.text = tagText createSubElement('firstChild') createSubElement('SecondChild') As expected, the output of this is: <document> <firstChild/> <SecondChild/> </document> However as you can notice the comment, I have no idea how to do set the text variable using this approach. Is using a class the only way to solve this? And if yes, can you give me some pointers on how to achieve this?

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  • Have I taken a wrong path in programming by being excessively worried about code elegance and style?

    - by Ygam
    I am in a major stump right now. I am a BSIT graduate, but I only started actual programming less than a year ago. I observed that I have the following attitude in programming: I tend to be more of a purist, scorning unelegant approaches to solving problems using code I tend to look at anything in a large scale, planning everything before I start coding, either in simple flowcharts or complex UML charts I have a really strong impulse on refactoring my code, even if I miss deadlines or prolong development times I am obsessed with good directory structures, file naming conventions, class, method, and variable naming conventions I tend to always want to study something new, even, as I said, at the cost of missing deadlines I tend to see software development as something to engineer, to architect; that is, seeing how things relate to each other and how blocks of code can interact (I am a huge fan of loose coupling) i.e the OOP thinking I tend to combine OOP and procedural coding whenever I see fit I want my code to execute fast (thus the elegant approaches and refactoring) This bothers me because I see my colleagues doing much better the other way around (aside from the fact that they started programming since our first year in college). By the other way around I mean, they fire up coding, gets the job done much faster because they don't have to really look at how clean their codes are or how elegant their algorithms are, they don't bother with OOP however big their projects are, they mostly use web APIs, piece them together and voila! Working code! CLients are happy, they get paid fast, at the expense of a really unmaintainable or hard-to-read code that lacks structure and conventions, or slow executions of certain actions (which the common reasoning against would be that internet connections are much faster these days, hardware is more powerful). The excuse I often receive is clients don't care about how you write the code, but they do care about how long you deliver it. If it works then all is good. Now, did my "purist" approach to programming may have been the wrong way to start programming? Should I just dump these purist concepts and just code the hell up because I have seen it: clients don't really care how beautifully coded it is?

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  • confusing fork system call

    - by benjamin button
    Hi, i was just checking the behaviour of fork system call and i found it very confusing. i saw in a website that Unix will make an exact copy of the parent's address space and give it to the child. Therefore, the parent and child processes have separate address spaces #include <stdio.h> #include <sys/types.h> int main(void) { pid_t pid; char y='Y'; char *ptr; ptr=&y; pid = fork(); if (pid == 0) { y='Z'; printf(" *** Child process ***\n"); printf(" Address is %p\n",ptr); printf(" char value is %c\n",y); sleep(5); } else { sleep(5); printf("\n ***parent process ***\n",&y); printf(" Address is %p\n",ptr); printf(" char value is %c\n",y); } } the output of the above program is : *** Child process *** Address is 69002894 char value is Z ***parent process *** Address is 69002894 char value is Y so from the above mentioned statement it seems that child and parent have separet address spaces.this is the reason why char value is printed separately and why am i seeing the address of the variable as same in both child and parent processes.? Please help me understand this!

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  • Why does C++ not allow multiple types in one auto statement?

    - by Walter
    The 2011 C++ standard introduced the new keyword auto, which can be used for defining variables instead of a type, i.e. auto p=make_pair(1,2.5); // pair<int,double> auto i=std::begin(c), end=std::end(c); // decltype(std::begin(c)) In the second line, i and end are of the same type, referred to as auto. The standard does not allow auto i=std::begin(container), e=std::end(container), x=*i; when x would be of different type. My question: why does the standard not allow this last line? It could be allowed by interpreting auto not as representing some to-be-decuded type, but as indicating that the type of any variable declared auto shall be deduced from its assigned value. Is there any good reason for the C++11 standard to not follow this approach? There is actually a use case for this, namely in the initialisation statement of for loops: for(auto i=std::begin(c), end=std::end(c), x=*i; i!=end; ++i, x+=*i) { ... } when the scope of the variables i, end, and x is limited to the for loop. AFAIK, this cannot be achieved in C++ unless those variables have a common type. Is this correct? (ugly tricks of putting all types inside a struct excluded) There may also be use cases in some variadic template applications.

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  • In Ruby, why does a method invocation not be able to be treated as a unit when "do" and "end" is use

    - by Jian Lin
    The following question is related to http://stackoverflow.com/questions/2127836/ruby-print-inject-do-syntax The question is, can we insist on using DO and END and make it work with puts or p? This works: a = [1,2,3,4] b = a.inject do |sum, x| sum + x end puts b # prints out 10 so, is it correct to say, inject is a class method of the Array class, which takes a block of code, and then returns a number. If so, then it should be no different from calling a function and getting back a return value: b = foo(3) puts b or b = circle.getRadius() puts b In the above two cases, we can directly say puts foo(3) puts circle.getRadius() so, there is no way to make it work directly by using the following 2 ways: a = [1,2,3,4] puts a.inject do |sum, x| sum + x end but it gives ch01q2.rb:7:in `inject': no block given (LocalJumpError) from ch01q2.rb:4:in `each' from ch01q2.rb:4:in `inject' from ch01q2.rb:4 grouping the method call using ( ) doesn't work either: a = [1,2,3,4] puts (a.inject do |sum, x| sum + x end) and this gives: ch01q3.rb:4: syntax error, unexpected kDO_BLOCK, expecting ')' puts (a.inject do |sum, x| ^ ch01q3.rb:4: syntax error, unexpected '|', expecting '=' puts (a.inject do |sum, x| ^ ch01q3.rb:6: syntax error, unexpected kEND, expecting $end end) ^ finally, the following version works: a = [1,2,3,4] puts a.inject { |sum, x| sum + x } but why doesn't the grouping of the method invocation using ( ) work? What if a programmer insists that he uses do and end, can it be made to work directly with p or puts, without an extra temporary variable?

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  • property names are different from original Object in the silverlight

    - by kwon
    Following is part of service layer which is provided by WCF service : [Serializable] public class WaitInfo { private string roomName; private string pName; private string tagNo; public string RoomName { get { return roomName; } set { this.roomName = value; } } public string PName { get { return pName; } set { this.pName = value; } } public string TagNo { get { return tagNo; } set { this.tagNo = value; } } } public class Service1 : IService1 { public List<WaitInfo> GetWaitingList() { MyDBDataContext db = new MyDBDataContext(); var query = from w in db.WAIT_INFOs select new WaitInfo { TagNo = w.PATIENT_INFO.TAG_NO, RoomName= w.ROOM_INFO.ROOM_NAME, PName= w.PATIENT_INFO.P_NAME }; List<WaitInfo> result = query.ToList(); return result; } And following is codebehind part of UI layer which is provided by Silverlight public MainPage() { InitializeComponent(); Service1Client s = new Service1Client(); s.GetWaitingListCompleted += new EventHandler<GetWaitingListByCompletedEventArgs>( s_GetWaitingListCompleted); s.GetWaitingListAsync(); } void s_GetWaitingListCompleted(object sender, RadControlsSilverlightApplication1.ServiceReference2.GetWaitingListByCompletedEventArgs e) { GridDataGrid.ItemsSource = e.Result; } And following is xaml code in Silverlight page <Grid x:Name="LayoutRoot"> <data:DataGrid x:Name="GridDataGrid"></data:DataGrid> </Grid> Is is very simple code, however what I am thinking weird is property name of object at "e.Result" in the code behind page. In the service layer, although properties' names are surely "RoomName, PName, TagNo", in the silverlight properties' names are "roomName, pName, tagNo" which are private variable name of the WaitingList Object. Did I something wrong? Thanks in advance.

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  • When do instance variables get initialized and values assigned?

    - by AKh
    When doees the instance variable get initialized? Is it after the constructor block is done or before it? Consider this example: public abstract class Parent { public Parent(){ System.out.println("Parent Constructor"); init(); } public void init(){ System.out.println("parent Init()"); } } public class Child extends Parent { private Integer attribute1; private Integer attribute2 = null; public Child(){ super(); System.out.println("Child Constructor"); } public void init(){ System.out.println("Child init()"); super.init(); attribute1 = new Integer(100); attribute2 = new Integer(200); } public void print(){ System.out.println("attribute 1 : " +attribute1); System.out.println("attribute 2 : " +attribute2); } } public class Tester { public static void main(String[] args) { Parent c = new Child(); ((Child)c).print(); } } OUTPUT: Parent Constructor Child init() parent Init() Child Constructor attribute 1 : 100 attribute 2 : null When the memory for the atribute 1 & 2 are allocated in the heap ? Curious to know why is attribute 2 is NULL ? Are there any design flaws?

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  • ViewController access data

    - by Giovanni Filaferro
    Today i would ask you if there is a way to call a method of another view controller just not initializing it or just how to get that viewController as a global variable declared in .h file. Help me please. I'm using a PageViewController and I have to use a method of the contentViewController alredy initialized. here I create my ViewControllers: - (void)createTheContent { NSLog(@"createTheContent"); pageController = nil; //[pageController removeFromParentViewController]; //[pageController awakeFromNib]; NSDictionary *options = [NSDictionary dictionaryWithObject:[NSNumber numberWithInteger:UIPageViewControllerSpineLocationMin] forKey: UIPageViewControllerOptionSpineLocationKey]; self.pageController = [[UIPageViewController alloc] initWithTransitionStyle:UIPageViewControllerTransitionStylePageCurl navigationOrientation:UIPageViewControllerNavigationOrientationHorizontal options: options]; pageController.dataSource = self; [[pageController view] setFrame:CGRectMake(0, 0, 320, 365)]; initialViewController = [self viewControllerAtIndex:0]; NSMutableArray *viewControllers = [NSArray arrayWithObject:initialViewController]; [pageController setViewControllers:viewControllers direction:UIPageViewControllerNavigationDirectionForward animated:NO completion:nil]; [self addChildViewController:pageController]; [[self view] addSubview:[pageController view]]; [pageController didMoveToParentViewController:self]; } here are my propertys in .h file: contentViewController *initialViewController; } //Page View Controller Properties @property (strong, nonatomic) UIPageViewController *pageController; @property (strong, nonatomic) NSArray *pageContent; @property (strong, nonatomic) NSMutableArray *pageStrings; @property (strong, nonatomic) id dataObject;

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  • Rotate MapView in Android

    - by Matthew B.
    I am writing an Android app where one of the features is that the map will rotate according to the compass (i.e. if the phone is pointing east, the map will be oriented so that the east side of the map is on top). Previous answers that I have found suggested over writing the onDraw() method in mapView, however, the api changed the method to final so it cannot be overwritten. As a result I have tried to overwrite the dispatchDraw() method like so: Note: -compass is a boolean that if true, rotate the view -bearing is a float variable that has the degrees that the view should rotate protected void dispatchDraw(Canvas canvas) { canvas.save(); if (compass) { final float w = this.getWidth(); final float h = this.getHeight(); final float scaleFactor = (float)(Math.sqrt(h * h + w * w) / Math.min(w, h)); final float centerX = w / 2.0f; final float centerY = h / 2.0f; canvas.rotate(bearing, centerX, centerY); canvas.scale(scaleFactor, scaleFactor, centerX, centerY); } super.dispatchDraw(canvas); canvas.restore(); }

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  • How can I set up an editor to work with Git on Windows?

    - by Patrick McElhaney
    I'm trying out Git on Windows. I got to the point of trying "git commit" and I got this error: Terminal is dumb but no VISUAL nor EDITOR defined. Please supply the message using either -m or -F option. So I figured out I need to have an environment variable called EDITOR. No problem. I set it to point to Notepad. That worked, almost. The default commit message opens in Notepad. But Notepad doesn't support bare line feeds. I went out and got Notepad++. But I can't figure out how to get Notepad++ set up as the %EDITOR% in such a way that it works with Git as expected. I'm not married to Notepad++. At this point I couldn't care less what editor I use. I just want to be able to type my commit messages without using -m. So, for those of you using Git on Windows: What (free) tool do you use to edit your commit message, and what do you get when you type echo %EDITOR% at the command prompt?

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  • proper use of volatile keyword

    - by luke
    I think i have a pretty good idea about the volatile keyword in java, but i'm thinking about re-factoring some code and i thought it would be a good idea to use it. i have a class that is basically working as a DB Cache. it holds a bunch of objects that it has read from a database, serves requests for those objects, and then occasionally refreshes the database (based on a timeout). Heres the skeleton public class Cache { private HashMap mappings =....; private long last_update_time; private void loadMappingsFromDB() { //.... } private void checkLoad() { if(System.currentTimeMillis() - last_update_time > TIMEOUT) loadMappingsFromDB(); } public Data get(ID id) { checkLoad(); //.. look it up } } So the concern is that loadMappingsFromDB could be a high latency operation and thats not acceptable, So initially i thought that i could spin up a thread on cache startup and then just have it sleep and then update the cache in the background. But then i would need to synchronize my class (or the map). and then i would just be trading an occasional big pause for making every cache access slower. Then i thought why not use volatile i could define the map reference as volatile private volatile HashMap mappings =....; and then in get (or anywhere else that uses the mappings variable) i would just make a local copy of the reference: public Data get(ID id) { HashMap local = mappings; //.. look it up using local } and then the background thread would just load into a temp table and then swap the references in the class HashMap tmp; //load tmp from DB mappings = tmp;//swap variables forcing write barrier Does this approach make sense? and is it actually thread-safe?

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  • Drawing Quadratic Bezier circles with a given radius: how to determine control points

    - by Casey
    Just to clarify; the code below works, but I don't understand where the formula for the variable "controlRadius" comes from. I wrote this function by dissecting an example I found elsewhere, but I can't find any explanation and the original code comments were not able to be translated. Thanks in advance //returns an array of quadratic Bezier segments public static function generateCircularQuadraticBezierSegments(radius:Number, numControlPoints:uint, centerX:Number, centerY:Number):Array { var segments:Array = []; var arcLength:Number = 2 * Math.PI / numControlPoints; var controlRadius:Number; var segment:QuadraticBezierSegment; for (var i:int = 0; i < numControlPoints; i++) { var startX:Number = centerX + radius * Math.cos(arcLength * i); var startY:Number = centerY + radius * Math.sin(arcLength * i); //control radius formula //where does it come from, why does it work? controlRadius = radius / Math.cos(arcLength * .5); //the control point is plotted halfway between the arcLength and uses the control radius var controlX:Number = centerX + controlRadius * Math.cos(arcLength * (i + 1) - arcLength * .5); var controlY:Number = centerY + controlRadius * Math.sin(arcLength * (i + 1) - arcLength * .5); var endX:Number = centerX + radius * Math.cos(arcLength * (i + 1)); var endY:Number = centerY + radius * Math.sin(arcLength * (i + 1)); segment = new QuadraticBezierSegment(new Point(startX, startY), new Point(controlX, controlY), new Point(endX, endY)); segments.push(segment); } return segments; }

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  • Java generic Comparable where subclasses can't compare to eachother

    - by dege
    public abstract class MyAbs implements Comparable<MyAbs> This would work but then I would be able to compare class A and B with each other if they both extend MyAbs. What I want to accomplish however is the exact opposite. So does anyone know a way to get the generic type to be the own class? Seemed like such a simple thing at first... Edit: To explain it a little further with an example. Say you have an abstract class animals, then you extend it with Dogs and ants. I wouldn't want to compare ants with Dogs but I however would want to compare one dog with another. The dog might have a variable saying what color it is and that is what I want to use in the compareTo method. However when it comes to ants I would rather want to compare ant's size than their color. Hope that clears it up. Could possibly be a design flaw however.

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  • Iterating XML nodes using VBA

    - by ydobonmai
    Note:- It just might be a iterating XML nodes using VBA question. Please look at the bottom of this question. It would be good If we can iterate without using MSXML2.DOMDocument I see the this question which answers part of my question on how to retrieve the CustomXMLPart. However, I am not able to iterate through the Xml. That way, this might not be specific to CustomXmlPart, It just might be a iterating XML using VBA question. Following is the XML I have in my CustomXMLPart. <Items> <Item1>Item1</Item1> <Item2>Item2</Item2> <Item3>Item3</Item3> </Items> This is how I add the above XML as CustomXmlPart:- static void AddCustomTableXmlPart(WordprocessingDocument document) { MainDocumentPart mainDocumentPart = document.MainDocumentPart; XDocument itemXml = GetItemsAsCustomXML(); if (mainDocumentPart.GetPartsCountOfType<CustomXmlPart>() > 0) mainDocumentPart.DeleteParts<CustomXmlPart>(mainDocumentPart.CustomXmlParts); //Add a new customXML part and then add content var customXmlPart = mainDocumentPart.AddCustomXmlPart(CustomXmlPartType.CustomXml); //copy the XML into the new part... using (var ts = new StreamWriter(customXmlPart.GetStream())) { ts.Write(itemXml.ToString()); ts.Flush(); } } and this is how I am accessing it in the macro:- Dim itemNode As xmlNode Dim itemChildren As XMLNodes ' The below line throws a run-time error 'Run-time error '13' - 'type mismatch ' not sure why. **Set itemChildren= ActiveDocument.CustomXMLParts(ActiveDocument.CustomXMLParts.Count).SelectSingleNode("//Items").ChildNodes** Interestingly, when I quick watch ActiveDocument.CustomXMLParts(ActiveDocument.CustomXMLParts.Count).SelectSingleNode("//Items").ChildNodes, I see child items in the quick watch window. Is the assignment to the itemChildren variable incorrect? I want to iterate through all the items and get get text for all of them. Could anybody help?

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  • VS2010 Implement Generic Interface expansion doesn't use specified type

    - by TJB
    Using the release version of Visual Studio 2010 I think there's a difference in the "Implement Interface" expansion from VS2008 If I speicify an interface and implement it in a class as so: public interface IRepository<T> where T : IModel { T Get<T>(int id); void Update<T>(); int Add<T>(T item); } public class MockRepository : IRepository<MockUser> { // ... } Then use the "Implement Interface" expansion and get this: public class MockRepository : IRepository<MockUser> { public T Get<T>(int id) { throw new NotImplementedException(); } public void Update<T>() { throw new NotImplementedException(); } public int Add<T>(T item) { throw new NotImplementedException(); } } Instead of what I expected public class MockRepository : IRepository<MockUser> { public MockUser Get<MockUser>(int id) { throw new NotImplementedException(); } public void Update<MockUser>() { throw new NotImplementedException(); } public int Add<MockUser>(MockUser item) { throw new NotImplementedException(); } } The IDE uses the type variable name from the generic interface definition T instead of the specified concrete type MockUser. Is this a bug? Or is something new just for VS2010 / .Net 4.0?

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  • Performing calculations by subsets of data in R

    - by Vivi
    I want to perform calculations for each company number in the column PERMNO of my data frame, the summary of which can be seen here: > summary(companydataRETS) PERMNO RET Min. :10000 Min. :-0.971698 1st Qu.:32716 1st Qu.:-0.011905 Median :61735 Median : 0.000000 Mean :56788 Mean : 0.000799 3rd Qu.:80280 3rd Qu.: 0.010989 Max. :93436 Max. :19.000000 My solution so far was to create a variable with all possible company numbers compns <- companydataRETS[!duplicated(companydataRETS[,"PERMNO"]),"PERMNO"] And then use a foreach loop using parallel computing which calls my function get.rho() which in turn perform the desired calculations rhos <- foreach (i=1:length(compns), .combine=rbind) %dopar% get.rho(subset(companydataRETS[,"RET"],companydataRETS$PERMNO == compns[i])) I tested it for a subset of my data and it all works. The problem is that I have 72 million observations, and even after leaving the computer working overnight, it still didn't finish. I am new in R, so I imagine my code structure can be improved upon and there is a better (quicker, less computationally intensive) way to perform this same task (perhaps using apply or with, both of which I don't understand). Any suggestions?

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