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  • boost::enable_if class template method

    - by aaa
    I got class with template methods that looks at this: struct undefined {}; template<typename T> struct is_undefined : mpl::false_ {}; template<> struct is_undefined<undefined> : mpl::true_ {}; template<class C> struct foo { template<class F, class V> typename boost::disable_if<is_undefined<C> >::type apply(const F &f, const V &variables) { } template<class F, class V> typename boost::enable_if<is_undefined<C> >::type apply(const F &f, const V &variables) { } }; apparently, both templates are instantiated, resulting in compile time error. is instantiation of template methods different from instantiation of free functions? I have fixed this differently, but I would like to know what is up. Thank you

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  • Help me understand Dispose() implementation code from MSDN

    - by Benny
    the following code is from MSDN: Idisposable pattern protected virtual void Dispose(bool disposing) { // If you need thread safety, use a lock around these // operations, as well as in your methods that use the resource. if (!_disposed) { if (disposing) { if (_resource != null) _resource.Dispose(); Console.WriteLine("Object disposed."); } // Indicate that the instance has been disposed. _resource = null; _disposed = true; } } why the following statement: _resource = null; _disposed = true; are not enclosed by if (disposing) statement block? for me i would probably write like this: if (disposing) { if (_resource != null) { _resource.Dispose(); _resource = null; _disposed = true; } Console.WriteLine("Object disposed."); } anything wrong with my version?

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  • two HashMap iteration

    - by user431276
    I have two HashMaps and I can iterate both hashmaps with following code Iterator it = mp.entrySet().iterator(); while (it.hasNext()) { Map.Entry pairs = (Map.Entry)it.next(); String firstVal = pairs.getValue(); } Iterator it2 = mp2.entrySet().iterator(); while (it2.hasNext()) { Map.Entry pairs2 = (Map.Entry)it.next(); String SecondVal = pairs2.getValue(); } myFunction(firstVal, SecondVal) Is there anyway to iterate two hashmaps at the same time without using two loops? Currently, I have a method that accepts two parameters and each parameter value is stored in first and second hashmap. I have to iterate first hash then second to get values. I think there must be a good way to do it but I don't know :( P.S: there could be some errors in above code as this is just an example to explain my problem. Each iterator is a method in original program and accept one parameter. I couldn't copy past real time functions as they are HUGE !

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  • Where are the readonly/const in .NET?

    - by acidzombie24
    In C++ you'll see void func(const T& t) everywhere. However, i havent seen anything similar in .NET. Why? I have notice a nice amount of parameters using struct. But i see no functions with readonly/const. In fact now that i tried it i couldnt use those keywords to make a function that promises to not modify a list being passed in. Is there no way to promise the caller that this function will never modify the contents of list? Is there no way to say to call code and say this list should never be modified? (I know i can clone the list or look at documentation but i like compile errors sometime)

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  • Double indirection and structures passed into a function

    - by ZPS
    I am curious why this code works: typedef struct test_struct { int id; } test_struct; void test_func(test_struct ** my_struct) { test_struct my_test_struct; my_test_struct.id=267; *my_struct = &my_test_struct; } int main () { test_struct * main_struct; test_func(&main_struct); printf("%d\n",main_struct->id); } This works, but pointing to the memory address of a functions local variable is a big no-no, right? But if i used a structure pointer and malloc, that would be the correct way, right? void test_func(test_struct ** my_struct) { test_struct *my_test_struct; my_test_struct = malloc(sizeof(test_struct)); my_test_struct->id=267; *my_struct = my_test_struct; } int main () { test_struct * main_struct; test_func(&main_struct); printf("%d\n",main_struct->id); }

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  • Floating point comparison in STL, BOOST

    - by Paul
    Is there in the STL or in Boost a set of generic simple comparison functions? The one I found are always requiring template parameters, and/or instantiation of a struct template. I'm looking for something with a syntax like : if ( is_greater(x,y) ) { ... } Which could be implemented as : template <typename T> bool is_greater(const T& x, const T& y) { return x > y + Precision<T>::eps; }

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  • CodeIgniter Validation in Library does not accept callback.

    - by Lukas Oppermann
    Hey guys, my problem is the following: I am writing a login library. This library has a function _validation() and this uses the validation library to validate the data. With using normal validation methods it works just fine, but using a callback function just does not work. It is not called. I call it like this. $this->CI->form_validation->set_rules('user', 'Username', 'required|callback__check_user'); The functions name is _check_user and it uses the username _check_user($user). The function itself works fine and I can also call it in the class ($this-_check_user('username')) with a working result. I am guessing, there might be a problem because I am not workin in a controller so I have a CI instance $this-CI instead of just the original instance $this- Does anyone have a clue how to fix this? Thanks in advance.

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  • Setting ID to a control inside repeater itemtemplate

    - by toraan
    Inside repeater's itemtemplate I have a Panel server control. I need to assign special Id for it, because I need to work with some javascript functions that use this Id. In repeater ItemDataBound event I have this: pnlButtonsPanel.ID = pnlButtonsPanel.ID + DataBinder.Eval(e.Item.DataItem, "ID"); But this solution is not good because after a postback the page is re -rendered and I lose the new ID. (And I don't want to rebind repeater after every postback) I tried to set the ID on aspx page like that: <asp:Panel id='<%# Eval("ID") %>' and some other variations but always get compile errors.

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  • Rails setting OR conditions in validate_presence_of in a model?

    - by Jty.tan
    In a rails model, is it possible to do something like class Example < ActiveRecord::Base #associations validates_presence_of :item_id, (:user_id OR :user_email) #functions end Where the model has 3 columns of :item_id, :user_id, and :user_email? I want the model to be valid as long as I have a :user_id or a :user_email. Idea being that if the item is recommended to a person who isn't currently signed up, it can be associated via email address for when the recommended person signs up. Or is there a different method that I can use instead?

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  • When did C++ get nested classes?

    - by Parappa
    Somehow I never noticed until today that C++ supports nested classes. This surprised me because when I was learning C++ back in the '90s, I specifically remember nested classes being something that Object Pascal and Java had, but which C++ did not. I asked an old programmer friend about it and he concurred that he recalls C++ not having nested classes. Is my recollection of C++ not having nested classes mistaken, or were they actually added to the standard at some point in the past fifteen years? I tried searching Google for information on this topic and I haven't come up with anything helpful yet. It could also be that I'm thinking of nested functions, which Pascal certainly supports but C does not.

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  • Example from: "Javascript - The Good Parts"

    - by Matrym
    What "ugliness" does the following solve? There's something I'm not getting, and I'd appreciate help understanding what it is. For example, by augmenting Function.prototype, we can make a method available to all functions: Function.prototype.method = function (name, func) { this.prototype[name] = func; return this; }; By augmenting Function.prototype with a method method, we no longer have to type the name of the prototype property. That bit of ugliness can now be hidden.

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  • Instance where embedded C++ compilers don't support multiple inheritance?

    - by Nathan
    I read a bit about a previous attempt to make a C++ standard for embedded platforms where they specifically said multiple inheritance was bad and thus not supported. From what I understand, this was never implemented as a mainstream thing and most embedded C++ compilers support most standard C++ constructs. Are there cases where a compiler on a current embedded platform (i.e. something not more than a few years old) absolutely does not support multiple inheritance? I don't really want to do multiple inheritance in a sense where I have a child with two full implementations of a class. What I am most interested in is inheriting from a single implementation of a class and then also inheriting one or more pure virtual classes as interfaces only. This is roughly equivalent to Java/.Net where I can extend only one class but implement as many interfaces as I need. In C++ this is all done through multiple inheritance rather than being able to specifically define an interface and declare a class implements it.

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  • Is there a function that can read a php function post-parsing?

    - by Rob
    I've got a php file echoing hashes from a MySQL database. This is necessary for a remote program I'm using, but at the same time I need my other php script opening and checking it for specified strings POST parsing. If it checks for the string pre-parsing, it'll just get the MySQL query rather than the strings to look for. I'm not sure if any functions do this. Does fopen() read the file prior to parsing? or file_get_contents()? If so, is there a function that'll read the file after the php and mysql code runs? The file with the hashes query and echo is in the same directory as the php file reading it, if that makes a difference. Perhaps fopen reads it post-parse, and I've done something wrong, but at first I was storing the hashes directly in the file, and it was working fine. After I changed it to echo the contents of the MySQL table, it bugged out.

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  • Long IF tree with strings

    - by DalGr
    I have a C program which uses Lua for scripting. In order to keep readability and avoid importing several constants within the individual Lua states, I condense a large amount of functions within a simple call (such as "ObjectSet(id, "ANGLE", 45)"), by using an "action" string. To do this I have a large if tree comparing the action string to a list (such as "if(stringcompare(action, "ANGLE") ... else if (stringcompare(action, "X")... etc") This approach works well, and within the program it's not really slow, and is fairly quick to add a new action. But I kind of feel perfectionist. Is there a better way to do this in C? And having Lua in heavy use, maybe there is a way to use it for this purpose? (embedded "chunks" making a dictionary?) Although this part is mostly curiosity.

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  • Flash in VC++ Documentation

    - by Red Serpent
    Hi I am trying to host a flash object inside an CAxWindow, I have managed to insert a shockwaveflash (SWF) and its working fine. I am trying to find all available API's that are available in the flash ocx. I am unable to find any documentation for the functions in the IShockwaveFlash interface. I know that Adobe doesn't have a documentation for using flash in VC++ but I was wondering if anyone can point me to a place where I can find an UNOFFICIAL documentation for flash.ocx or code samples as the only API that I could find and I'm currently using is "PutMovie". Any help is appreciated...

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  • FluentNHibernate: returning an enum from a derived property

    - by Zen-C
    I'm using the automapping feature of FluentNHibernate and need a property that derives its return value. This property must return an Enum value, e.g. public virtual MyEnum MyDerivedProperty { get { MyEnum retval; // do some calculations return retval; } } Currently I get the following exception: NHibernate.PropertyNotFoundException: Could not find a setter for property 'MyDerivedProperty' ... If I add a setter then the database table involved requires the column to exist, even if that setter does nothing. It works fine when the return type is an int. Any ideas how I achieve this?

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  • Convert wide to long format in R

    - by Anthony
    My data has a long format similar to the one below: ID Language MotherTongue SpokenatHome HomeLang 1 English English English 1 French French 1 Polish Polish 2 Lebanese Lebanese Lebanese Labanese 2 Arabic Arabbic Here is the output I am looking for: ID Language1 Language2 Language 3 MotherTongue1 MotherTongue2 SpokenatHome1 HomeLan 1 English French Polish English Polish French English 2 Lebanese Arabic Labanese Arabic I'm using using the melt and dcast functions of the reshape2 package, but it does not work. Does anyone know how to do this? Thanks. df<-df[,c("OEN", "Langugae","MotherTongue", "SpokenatHome", "MainHomeLanguage")] dfl <- melt(df, id.vars=c("OEN", "Langugae"), measure.vars=c("MotherTongue", "SpokenatHome", "MainHomeLanguage"), variable.name="Language") dfw <- dcast(dfl, OEN ~ Langugae , value.var="value" )

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  • php, get an end date based on start date and number of months

    - by mike
    Hi! I need to calculate an end date based on todays date and a number of months. For example, todays date 04/01/2010 and the number of months is 6. Are there any functions I can use to do some math that would return "10/01/2010"? Also, I think it's important to note that I am storing the result in MySQL as a "DATETIME" so I guess I would have to do something with the time as well... ??? Thanks!

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  • Javascript: variable scope & the evils of globals

    - by Nick
    I'm trying to be good, I really am, but I can't see how to do it :) Any advice on how to not use a global here would be greatly appreciated. Let's call the global G. Function A Builds G by AJAX Function B Uses G Function C Calls B Called by numerous event handlers attached to DOM elements (type 1) Function D Calls B Called by numerous event handlers attached to DOM elements (type 2) I can't see how I can get around using a global here. The DOM elements (types 1 & 2) are created in other functions (E&F) which are unconnected with A. I don't want to add G to each event handler (because it's large and there's lots of these event handlers), and doing so would require the same kind of solution as I'm seeking here (i.e., getting G to E&F). The global G, BTW, is an array that is necessary to build other elements as they, in turn, are built by AJAX. I'm not convinced that a singleton is real solution, either. Thanks.

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  • Which JavaScript Libraries do not rely on a document and navigator object?

    - by Julian Weimer
    I'm currently looking for some libraries which might help me during iPhone Development using Appcelerator Titanium. I've heard that since version 1.0 it isn't dependant on webkit anymore and it makes app-development more exiting of course, please correct me if i'm wrong. As many people out there i love Javascript Frameworks such as JQuery and Mootools much, but they were build specifically to do a great job within a browser and most of the functionality is not needed within the environment Titanium now provides (DOM-Manipulation etc). Is there any other small library of useful functions i can use for development? Thx in advance.

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  • Java - Robot keyPress issue

    - by Trimbitas Sorin
    I'm trying to send keystrokes (like a virtual keyboard) from my Java code, but I encounter some issues. It works perfectly on normal applications (for example, Notepad, browsers, etc.), but not on games (fullscreen or windowed mode). This is the stripped code I'm using: import java.awt.Robot; import java.awt.AWTException; import java.awt.event.InputEvent; Robot robot; robot.keyPress(KeyEvent.VK_A); robot.keyRelease(KeyEvent.VK_A); How can this problem be fixed?

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  • Trying to find a good javascript function for hmac-sha1

    - by Darxval
    So i have been searching the web for a javascript source for an Hmac-sha1 algorithm. I saw Crypto's but i cant seem to get it to work, mainly because it has no idea what crypto means. (i copied the .js script functions into my script file) http://code.google.com/p/crypto-js/ I have my base64 encoded function already. that i got from here: http://nerds-central.blogspot.com/2007/01/fast-scalable-javascript-and-vbscript.html btw this for a twitter application using the new OAuth system. any help or links to where i can find anything on this would be helpful If you need me to elaborate let me know. thank you!

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  • If free() knows the length of my array, why can't I ask for it in my own code?

    - by Chris Cooper
    I know that it's a common convention to pass the length of dynamically allocated arrays to functions that manipulate them: void initializeAndFree(int* anArray, int length); int main(){ int arrayLength = 0; scanf("%d", &arrayLength); int* myArray = (int*)malloc(sizeof(int)*arrayLength); initializeAndFree(myArray, arrayLength); } void initializeAndFree(int* anArray, int length){ int i = 0; for (i = 0; i < length; i++) { anArray[i] = 0; } free(anArray); } but if there's no way for me to get the length of the allocated memory from a pointer, how does free() "automagically" know what to deallocate? Why can't I get in on the magic, as a C programmer? Where does free() get its free (har-har) knowledge from?

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  • How to handle this type of model validation in Ruby on Rails

    - by randombits
    I have a controller/model hypothetically named Pets. Pets has the following declarations: :belongs_to owner :has_many dogs :has_many cats Not the best example, but again, it demonstrates what I'm trying to solve. Now when a request comes in as an HTTP POST to http://127.0.0.1/pets, I want to create an instance of Pets. The restriction here is, if the user doesn't submit at least one dog or one cat, it should fail validation. It can have both, but it can't be missing both. How does one handle this in Ruby on Rails? Dogs don't care if cats exists and the inverse is also true. Can anyone show some example code of what the Pets model would look like to ensure that one or the other exists, or fail otherwise? errors.add also takes an attribute, in this case, there is no particular attribute that's failing. It's almost a 'virtual' combination that's missing.

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  • Will .NET 4.0 apps work on Win 2008 R2 Server Core?

    - by markus
    When Windows Server 2008 R2 was launched, the "server core" edition started to become useful to me, because it lets me deploy .NET background applications isolated on their own virtual machine instance with only a small fraction of all the disk space overhead of a default Windows Server installation, and very few Windows Updates. It comes with a subset of .NET 3.5 SP1 integrated (as an optional feature). Now that .NET 4.0 is released, the redistributables explicitly state that it's not support on Server Core. Any chance that there will be a separate download available for Server Core (e. g. without WPF) any time soon, has anybody heard about it?

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