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  • What is the proper way to declare a specialization of a template for another template type?

    - by Head Geek
    The usual definition for a specialization of a template function is something like this: class Foo { [...] }; namespace std { template<> void swap(Foo& left, Foo& right) { [...] } } // namespace std But how do you properly define the specialization when the type it's specialized on is itself a template? Here's what I've got: template <size_t Bits> class fixed { [...] }; namespace std { template<size_t Bits> void swap(fixed<Bits>& left, fixed<Bits>& right) { [...] } } // namespace std Is this the right way to declare swap? It's supposed to be a specialization of the template function std::swap, but I can't tell whether the compiler is seeing it as such, or whether it thinks that it's an overload of it or something.

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  • How do you parse text in Ruby on Rails and add classes to specific parts of it?

    - by codyvbrown
    I am a Rails novice and I'm creating an application that I'd love some help on. The app is for social reading. It enables a user to highlight a passage from a text then have that passage saved and bolded into the view for later reading by anyone else. I have no problem creating an if statement on whether a certain string of text is in a passage but how do I add a class to that string and have a group of these passages absorbed back into the view. Any strategic advice would be greatly appreciated.

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  • What is the best way to declare sorted association in grails domain classes ?

    - by fabien7474
    It seems that there are two different ways of declaring sorted associations in Grails : Method 1 (see here) using default sort order class Book { String title } class Author { static hasMany = [books : Book] static mapping = { books sort: "title"} } Method 2 (see here) using SortedSet class Book implements Comparable { String title int compareTo(obj) { title <=> obj.title } } class Author { SortedSet books static hasMany = [books : Book] } I am not sure which one to use and what is the difference (if any), pros and cons between using one against the other. I would appreciate any clarification. Thank you

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  • Designing different Factory classes (and what to use as argument to the factories!)

    - by devoured elysium
    Let's say we have the following piece of code: public class Event { } public class SportEvent1 : Event { } public class SportEvent2 : Event { } public class MedicalEvent1 : Event { } public class MedicalEvent2 : Event { } public interface IEventFactory { bool AcceptsInputString(string inputString); Event CreateEvent(string inputString); } public class EventFactory { private List<IEventFactory> factories = new List<IEventFactory>(); public void AddFactory(IEventFactory factory) { factories.Add(factory); } //I don't see a point in defining a RemoveFactory() so I won't. public Event CreateEvent(string inputString) { try { //iterate through all factories. If one and only one of them accepts //the string, generate the event. Otherwise, throw an exception. return factories.Single(factory => factory.AcceptsInputString(inputString)).CreateEvent(inputString); } catch (InvalidOperationException e) { throw new InvalidOperationException("No valid factory found to generate this kind of Event!", e); } } } public class SportEvent1Factory : IEventFactory { public bool AcceptsInputString(string inputString) { return inputString.StartsWith("SportEvent1"); } public Event CreateEvent(string inputString) { return new SportEvent1(); } } public class MedicalEvent1Factory : IEventFactory { public bool AcceptsInputString(string inputString) { return inputString.StartsWith("MedicalEvent1"); } public Event CreateEvent(string inputString) { return new MedicalEvent1(); } } And here is the code that runs it: static void Main(string[] args) { EventFactory medicalEventFactory = new EventFactory(); medicalEventFactory.AddFactory(new MedicalEvent1Factory()); medicalEventFactory.AddFactory(new MedicalEvent2Factory()); EventFactory sportsEventFactory = new EventFactory(); sportsEventFactory.AddFactory(new SportEvent1Factory()); sportsEventFactory.AddFactory(new SportEvent2Factory()); } I have a couple of questions: Instead of having to add factories here in the main method of my application, should I try to redesign my EventFactory class so it is an abstract factory? It'd be better if I had a way of not having to manually add EventFactories every time I want to use them. So I could just instantiate MedicalFactory and SportsFactory. Should I make a Factory of factories? Maybe that'd be over-engineering? As you have probably noticed, I am using a inputString string as argument to feed the factories. I have an application that lets the user create his own events but also to load/save them from text files. Later, I might want to add other kinds of files, XML, sql connections, whatever. The only way I can think of that would allow me to make this work is having an internal format (I choose a string, as it's easy to understand). How would you make this? I assume this is a recurrent situation, probably most of you know of any other more intelligent approach to this. I am then only looping in the EventFactory for all the factories in its list to check if any of them accepts the input string. If one does, then it asks it to generate the Event. If you find there is something wrong or awkward with the method I'm using to make this happen, I'd be happy to hear about different implementations. Thanks! PS: Although I don't show it in here, all the different kind of events have different properties, so I have to generate them with different arguments (SportEvent1 might have SportName and Duration properties, that have to be put in the inputString as argument).

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  • What is wrong with this simple type definition? (Expecting one more argument to...)

    - by fluteflute
    basic.hs: areaCircle :: Floating -> Floating areaCircle r = pi * r * r Command: *Main> :l basic.hs [1 of 1] Compiling Main ( Sheet1.hs, interpreted ) Sheet1.hs:2:15: Expecting one more argument to `Floating' In the type signature for `areaCircle': areaCircle :: Floating -> Floating Failed, modules loaded: none. I see that areaCircle :: Floating a => a -> a loads as expected. Why is the above version not acceptable?

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  • How to mimic polymorphism in classes with template methods (c++)?

    - by davide
    in the problem i am facing i need something which works more or less like a polymorphic class, but which would allow for virtual template methods. the point is, i would like to create an array of subproblems, each one being solved by a different technique implemented in a different class, but holding the same interface, then pass a set of parameters (which are functions/functors - this is where templates jump up) to all the subproblems and get back a solution. if the parameters would be, e.g., ints, this would be something like: struct subproblem { ... virtual void solve (double& solution, double parameter)=0; } struct subproblem0: public subproblem { ... virtual void solve (double& solution, double parameter){...}; } struct subproblem1: public subproblem { ... virtual void solve (double* solution, double parameter){...}; } int main{ subproblem problem[2]; subproblem[0] = new subproblem0(); subproblem[1] = new subproblem1(); double argument0(0), argument1(1), sol0[2], sol1[2]; for(unsigned int i(0);i<2;++i) { problem[i]->solve( &(sol0[i]) , argument0); problem[i]->solve( &(sol1[i]) , argument1); } return 0; } but the problem is, i need the arguments to be something like Arg<T1,T2> argument0(f1,f2) and thus the solve method to be something of the likes of template<T1,T2> solve (double* solution, Arg<T1,T2> parameter) which cant obviously be declared virtual ( so cant be called from a pointer to the base class)... now i'm pretty stuck and don't know how to procede...

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  • which lightweight SQL Server type could I use on my Dev machine for a C# VS2010 project?

    - by Greg
    Hi, Which lightweight SQL Server type could I use on my Dev machine for a C# VS2010 project? (e.g. sql server express, sql server ce, full version etc). That is, I'm running on a VMWare fusion instance on my MacBook, and just want something to develop against for a C# VS2010 project. I'm planning on having a simple database (not many tables) but will use Entity Framework. I haven't used SQL Server before so a quick pointer re what is the best database admin interface/app to use for the version you recommend (e.g. to create database, tables etc).

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  • Using enums or a set of classes when I know I have a finite set of different options?

    - by devoured elysium
    Let's say I have defined the following class: public abstract class Event { public DateTime Time { get; protected set; } protected Event(DateTime time) { Time = time; } } What would you prefer between this: public class AsleepEvent : Event { public AsleepEvent(DateTime time) : base(time) { } } public class AwakeEvent : Event { public AwakeEvent(DateTime time) : base(time) { } } and this: public enum StateEventType { NowAwake, NowAsleep } public class StateEvent : Event { protected StateEventType stateType; public MealEvent(DateTime time, StateEventType stateType) : base(time) { stateType = stateType; } } and why? I am generally more inclined to the first option, but I can't explain why. Is it totally the same or are any advantages in using one instead of the other? Maybe with the first method its easier to add more "states", altough in this case I am 100% sure I will only want two states: now awake, and now asleep (they signal the moments when one awakes and one falls asleep).

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  • Cannot implicitly convert type ... to ... problem

    - by Younes
    I have this code: public static IEnumerable<dcCustomer> searchCustomer(string Companyname) { TestdbDataContext db = new TestdbDataContext(); IEnumerable<dcCustomer> myCustomerList = (from Customer res in db.Customers where res.CompanyName == Companyname select res); return myCustomerList; } And whatever i try i keep getting the convert error. Error 1 Cannot implicitly convert type 'System.Collections.Generic.IEnumerable<ConnectionWeb.Customer>' to 'System.Collections.Generic.IEnumerable<ConnectionWeb.DAL.dcCustomer>'. An explicit conversion exists (are you missing a cast?) \\srv01\home$\Z****\Visual Studio 2008\Projects\ConnectionWeb\ConnectionWeb\DAL\dcCustomer.cs 63 20 ConnectionWeb I want to try get myCustomerList to keep the values in an enumerator and return it.

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  • Does generation of debug information to JSP classes add much to javac execution time?

    - by Rich
    Hi I am looking looking into the options for tweaking the performance of JBoss 5.1.0 and one of the options available to me is to disable the generation of debug information when compiling JSPs. I know that the presence/absence of debug information for the JVM makes no real difference, but does the generation of that debug information add much to compile time? Thanks in advance Richard

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  • Where do you extend classes in your rails application?

    - by ro
    Just about to extend the Array class with the following extension: class Array def shuffle! size.downto(1) { |n| push delete_at(rand(n)) } self end end However, I was wondering where a good place to keep these sort of extensions. I was thinking environment.rb or putting in its own file in the initializers directory.

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  • Return type value if RunTimeException has been thrown and not catched.

    - by Alfred
    I am using Gson to parse Json. What I don't understand what the return type will be if you don't catch the Runtime Exception. I was expecting it to be null, but it is not null when evaluating with a simple if statement. My code looks something like this: public X x() { return gson.fromJson(jsonString, X.class); } then from another function I call the function: public void y() { final X x = x(); if (x == null) { System.out.println("x == null") } } I was expecting x to be null, but it isn't because the print statement is not called? What is the value of x? How can if them. I have my problem by using a catch block in the x() function and returning null. But I am just wondering what the value of function x() is(if any?)? Hopefully I make any sense at all.

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  • What tricks can be used to type and edit code faster?

    - by Thomas
    As Jeff Atwood noted, we are typists first, programmers second. Fast typing and editing may not be essential to be a good programmer, but it certainly helps. I noticed that I consciously and subconsciously use various tricks to get my intent across to the computer as fast as possible. What tricks can be used to type and edit code faster? I'm hoping to collect a nice list here that we can all learn from, so that we can be ever so slightly more productive. One trick per answer please! (This is not about typing speed in general. There are other questions about that. It's also not about general answers like "learn your editor's shortcut keys". Think of this topic as micro-optimizations for specific cases. See my own answers for examples of what I mean.)

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  • Definitive list of protocols supported by the WebClient and WebRequest classes.

    - by the-locster
    The docs state: From WebRequest.Create Method The .NET Framework includes support for the http://, https://, and file:// URI schemes. Custom WebRequest descendants to handle other requests are registered with the RegisterPrefix method. However I've also been using this class to get files via ftp (not listed in the docs). Is there a definitive list of supported protocols documented anywhere? UPDATE: To clarify. Yes additional protocols can be plugged-in, but what is the standard/baseline set of protocols supported in the class framework assuming I haven't registered any others. e.g. sftp, tftp?

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  • help designing a method, should I use out or ref or return the type?

    - by Blankman
    I have a method that I will use in the following contexts: 1. User user = null; if(...) { user = defaultUser; SetUser(a,b,user); } else { SetUser(a,b,user); } SaveUser(user); So some cases are where user may be null, while in other cases it will already be initialized. How should I design the SetUser method? I currently have it like so, but this causes an error when user is null. public void SetUser(object a, object b, User user) { if(user == null) user = new User(); user.Security = a.security; user.Blah = b.type; }

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  • Sql: simultaneous aggregate from two tables

    - by Ash
    I have two tables: a Files table, which includes the file type, and a File Properties table, which references the file table via a foreign key. Sample Files table: | id | name | type | --------------------- | 1 | file1 | zip | | 2 | file2 | zip | | 3 | file3 | zip | | 4 | file4 | jpg | And the Properties table: | file_id | property | ----------------------- | 1 | x | | 2 | x | I want to make a query, which shows the count of each file type, and how many files of that type have a property. So in the example, the result would be | type | filecount | prop count | ---------------------------------- | zip | 3 | 2 | | jpg | 1 | 0 | I could accomplish this by select f.type, (select count(id) from files where type = f.type), count(fp.id) from files as f, file_properties as fp where f.id = fp.file_id group by f.type; But this seems very suboptimal and is very slow. Any better way to do this?

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  • Communicating between classes set up in nib, in code?

    - by cannyboy
    A beginner's question: If, in your nib, you have the File's Owner linked to the ViewController class, and you also have a NSObject-derived class, how do you communicate between the ViewController class and the NSObject class within code? For instance, suppose ScientificCalculatorView.xib looks like this File's Owner (class: ScientificCalculatorViewController) FirstResponder View Calculator (an object that has been linked to the Calculator class) Obviously, I'd want Calculator to be reusable, so it could be used with a NormalCalculatorViewController or something like that. So that UI and the calculator code are separate. Does Calculator even need to be in the nib? It's a beginners question, but I'm just trying to get my head around it.

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  • Why are changes to classes ignored after dom changes?

    - by Lg102
    I have a price grid that uses relative positioning to move a field around, beneath a box with: overflow: hidden;. In this is field, there are absolute-positioned boxes containing prices. When this box is hovered, the matching values above and left of the will change color. In order to achieve this, a class is toggled using jQuery. This initially works. However, after the grid is moved, the class change doesn't affect the block above the grid anymore. In the Chrome console, i can see the class being added, but it's css-styling isn't applied. No other styles for the element have changed. I am 100% sure there is no other style-rule influencing the element, it just stops responding to the change in class after the DOM has been altered. Can i 'refresh' the DOM somehow? Edit: I've tried to get the relevant code only: Adding the cell in the first place: $("#price_dates_cells").append("<div id='"+weekday[theBeginDate.getDay()]+"-"+theBeginDate.getDate()+"-"+(theBeginDate.getMonth()-1)+"' class='datecell' style='left: "+( Math.floor( difference / ( 3600 * 24 * 1000) ) * ( cellwidth ) )+"px'>"+weekday[theBeginDate.getDay()]+"<br>"+theBeginDate.getDate()+" "+yearmonth[theBeginDate.getMonth()]+"</div>"); Toggle the class: var str_element = "#"+weekday[Bdate.getDay()]+"-"+Bdate.getDate()+"-"+(Bdate.getMonth()-1); $(str_element).toggleClass("red"); and the movement that seems to cause the problem: $('#price_grid').animate({"top": (( ( horizontalMovement ) * cellheight)) }, 'fast', 'linear');

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  • How do I do multiple has_and_belongs_to_many associations between the same two classes?

    - by Ermin
    I have the following setup: class Publication < ActiveRecord::Base has_and_belongs_to_many :authors, :class_name=>'Person', :join_table => 'authors_publications' has_and_belongs_to_many :editors, :class_name=>'Person', :join_table => 'editors_publications' end class Person < ActiveRecord::Base has_and_belongs_to_many :publications end With this setup I can do stuff like Publication.first.authors. But if I want to list all publications in which a person is involved Person.first.publications, an error about a missing join table people_publications it thrown. How could I fix that? Should I maybe switch to separate models for authors and editors? It would however introduce some redundancy to the database, since a person can be an author of one publication and an editor of another.

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  • How to process <input type="file" name="test1[f]" /> in PHP?

    - by user198729
    var_dump($_FILES) gives the following: array 'test1' => array 'name' => array 'f' => string 'ntuser.dat.LOG' (length=14) 'type' => array 'f' => string 'application/octet-stream' (length=24) 'tmp_name' => array 'f' => string 'D:\wamp\tmp\php223.tmp' (length=22) 'error' => array 'f' => int 0 'size' => array 'f' => int 0 Why is http designed this way?How can I get the file by $_FILES['test1']['f']?

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  • jQuery: Adding class to the li element after the link is clicked, and deselecting all other classes

    - by Oleg Tarasenko
    Hi, I am generating menu with such tags: <div class="animatedtabs"> <ul> {% for item in menu_items %} <li><a href="{{ item.url }}" title="{{ item.name }}"><span>{{ item.name }}</span></a></li> {% endfor %} </ul> </div> What I want to do, I want to add class="selected" to li, after the link is clicked, and to remove all other class="selected" on other li's... Also I wonder, how to show menu in the way, so the first item is selected by default... But then when another linked is clicked, then class="selected" is toggled

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  • How do I make Pseudo classes work with Internet Explorer 7/8?

    - by Mel
    I've written the following code to create a three-column layout where the first and last columns have no left and right margins respectively: #content { background-color:#edeff4; margin:0 auto 30px auto; padding:0 30px 30px 30px; width:900px; } .column { float:left; margin:0 20px; } #content .column:nth-child(1) { margin-left:0; } #content .column:nth-child(3) { margin-right:0; } The problem is that this code does not work in Internet Explorer 7 and 8? The only pseudo class I can use with IE (in this case) would be "first-child," but this does not eliminate the right margin on the third and last column. Does anyone know of a way I can make this code work on IE 7/8?

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  • Grails unit testing domain classes with Set properties - is this safe?

    - by Ali G
    I've created a domain class in Grails like this: class MyObject { static hasMany = [tags: String] // Have to declare this here, as nullable constraint does not seem to be honoured Set tags = new HashSet() static constraints = { tags(nullable: false) } } Writing unit tests to check the size and content of the MyObject.tags property, I found I had to do the following: assertLength(x, myObject.tags as Object[]) assertEquals(new HashSet([...]), myObject.tags) To make the syntax nicer for writing the tests, I implemented the following methods: void assertEquals(List expected, Set actual) { assertEquals(new HashSet(expected), actual) } void assertLength(int expected, Set set) { assertLength(expected, set as Object[]) } I can now call the assertLength() and assertEquals() methods directly on an instance of Set, e.g. assertLength(x, myObject.tags) assertEquals([...], myObject.tags) I'm new to Groovy and Grails, so unaware how dangerous method overloading like this is. Is it safe? If so, I'm slightly* surprised that these methods (or similar) aren't already available - please let me know if they are. * I can see how these methods could also introduce ambiguity if people weren't expecting them. E.g. assertLength(1, set) always passes, no matter what the content of set

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  • What's wrong with addlistener... how do i fire my event

    - by KoolKabin
    I am using the following functions to do my task. It works fine when cursor moves away from textbox but if i want to fire the same event from code say like next function i get error... function addEvent( obj, type, fn ) { if (obj.addEventListener) { obj.addEventListener( type, fn, false ); } else if (obj.attachEvent) { obj["e"+type+fn] = fn; obj[type+fn] = function() { obj"e"+type+fn; } obj.attachEvent( "on"+type, obj[type+fn] ); } else { obj["on"+type] = obj["e"+type+fn]; } } function addEventByName(ObjName, event, func){ MyEle = document.getElementsByName(ObjName); addEvent(MyEle[0], event, func); } addEventByName("txtBox", 'blur', function(){ alert('hello'); }); function fire(){ x = document.getElementsByName('txtBox')[0]; x.blur(); //gives error x.onblur(); //gives error }

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