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  • Does this mimic perfectly a function template specialization?

    - by zeroes00
    Since the function template in the following code is a member of a class template, it can't be specialized without specializing the enclosing class. But if the compiler's full optimizations are on (assume Visual Studio 2010), will the if-else-statement in the following code get optimized out? And if it does, wouldn't it mean that for all practical purposes this IS a function template specialization without any performance cost? template<typename T> struct Holder { T data; template<int Number> void saveReciprocalOf(); }; template<typename T> template<int Number> void Holder<T>::saveReciprocalOf() { //Will this if-else-statement get completely optimized out if(Number == 0) data = (T)0; else data = (T)1 / Number; } //----------------------------------- void main() { Holder<float> holder; holder.saveReciprocalOf<2>(); cout << holder.data << endl; }

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  • F# Inline Function Specialization

    - by Ben
    Hi, My current project involves lexing and parsing script code, and as such I'm using fslex and fsyacc. Fslex LexBuffers can come in either LexBuffer<char> and LexBuffer<byte> varieties, and I'd like to have the option to use both. In order to user both, I need a lexeme function of type ^buf - string. Thus far, my attempts at specialization have looked like: let inline lexeme (lexbuf: ^buf) : ^buf -> string where ^buf : (member Lexeme: char array) = new System.String(lexbuf.Lexeme) let inline lexeme (lexbuf: ^buf) : ^buf -> string where ^buf : (member Lexeme: byte array) = System.Text.Encoding.UTF8.GetString(lexbuf.Lexeme) I'm getting a type error stating that the function body should be of type ^buf -> string, but the inferred type is just string. Clearly, I'm doing something (majorly?) wrong. Is what I'm attempting even possible in F#? If so, can someone point me to the proper path? Thanks!

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  • Function pointers in Objective-C

    - by Stefan Klumpp
    I have the following scenario: Class_A - method_U - method_V - method_X - method_Y Class_B - method_M - method_N HttpClass - startRequest - didReceiveResponse // is a callback Now I want to realize these three flows (actually there are many more, but these are enough to demonstrate my question): Class_A :: method_X -> HttpClass :: startRequest:params -> ... wait, wait, wait ... -> HttpClass :: didReceiveResponse -> Class_A :: method_Y:result and: Class_A :: method_U -> HttpClass :: startRequest:params -> ... wait, wait, wait ... -> HttpClass :: didReceiveResponse -> Class_A :: method_V:result and the last one: Class_B :: method_M -> HttpClass :: startRequest:params -> ... wait, wait, wait ... -> HttpClass :: didReceiveResponse -> Class_B :: method_N:result Please note, that the methods in Class_A and Class_B have different names and functionality, they just make us of the same HttpClass. My solution now would be to pass a C function pointer to startRequest, store it in the HttpClass and when didReceiveResponse gets called I invoke the function pointer and pass the result (which will always be a JSON Dictionary). Now I'm wondering if there can be any problems using plain C or if there are better solutions doing it in a more Objective-C way. Any ideas?

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  • Problem with function calls [javascript]

    - by Samuel
    <script language="javascript"> function toggle(id) { alert('call'); if (document.getElementById(id).style.display == "none") { alert('now visible'); document.getElementById(id).style.display = ""; } else { alert('now invisible'); document.getElementById(id).style.display = "none"; } } </script> </head> <body onload="toggle('image1');alert('test_body');toggle('image2')"> <script language="javascript"> alert('test_pre_function'); toggle('image1'); alert('test_after_function'); toggle('image2'); </script> Looks like a lot of code but it's pretty simple so i think most of you won't have troubles with it. toggle() should toggle the display status of divs containing images. When the user enters the site the divs should hide, when everything is loaded the divs should show up. (onload) Strangely enough, the funtion in the body (not in the body tag) only work half, i get and alert 'test_pre_function' and i get an alert 'call' (out of the function), but that's it. The code in the body tag runs just fine. I find this weird because it's supposed to do exactly the same twice and one time it runs, another time not, so i guess i must have made some stupid mistake. Thanks for any help!

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  • Undeclared - 'first use in function'

    - by Ragunath Jawahar
    I'm new to Objective-C, though I have a very good hand in Android. I'm trying to make a call to a method but it gives me 'first use in function'. I know I'm making a silly mistake but experts could figure it out easily. RootViewController.h #import <UIKit/UIKit.h> #import "ContentViewController.h" @interface RootViewController : UITableViewController { ContentViewController *contentViewController; } @property (nonatomic, retain) ContentViewController *contentViewController; - (NSString*)getContentFileName:(NSString*)title; //<--- This function declartion @end RootViewController.m #import "RootViewController.h" #import "HAWATAppDelegate.h" #import "ContentViewController.h" @implementation RootViewController @synthesize contentViewController; ... more methods ... #pragma mark - #pragma mark Table view delegate - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { HAWATAppDelegate *appDelegate = (HAWATAppDelegate *)[[UIApplication sharedApplication] delegate]; NSString *title = (NSString *) [appDelegate.titles objectAtIndex:indexPath.row]; NSString *fileName = getContentFileName:title; //<--- Here is the error ... } - (NSString*) getContentFileName:(NSString*)title { return [title lowercaseString]; } @end There must be a simple thing I'm missing. Please let me know. Thanks in advance.

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  • C vs C++ function questions

    - by james
    I am learning C, and after starting out learning C++ as my first compiled language, I decided to "go back to basics" and learn C. There are two questions that I have concerning the ways each language deals with functions. Firstly, why does C "not care" about the scope that functions are defined in, whereas C++ does? For example, int main() { donothing(); return 0; } void donothing() { } the above will not compile in a C++ compiler, whereas it will compile in a C compiler. Why is this? Isn't C++ mostly just an extension on C, and should be mostly "backward compatible"? Secondly, the book that I found (Link to pdf) does not seem to state a return type for the main function. I check around and found other books and websites and these also commonly do not specify return types for the main function. If I try to compile a program that does not specify a return type for main, it compiles fine (although with some warnings) in a C compiler, but it doesn't compile in a C++ compiler. Again, why is that? Is it better style to always specify the return type as an integer rather than leaving it out? Thanks for any help, and just as a side note, if anyone can suggest a better book that I should buy that would be great!

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  • IoC - Dynamic Composition of object instances

    - by Joshua Starner
    Is there a way using IoC, MEF [Imports], or another DI solution to compose dependencies on the fly at object creation time instead of during composition time? Here's my current thought. If you have an instance of an object that raises events, but you are not creating the object once and saving it in memory, you have to register the event handlers every time the object is created. As far as I can tell, most IoC containers require you to register all of the classes used in composition and call Compose() to make it hook up all the dependencies. I think this may be horrible design (I'm dealing with a legacy system here) to do this due to the overhead of object creation, dependency injection, etc... but I was wondering if it was possible using one of the emergent IoC technologies. Maybe I have some terminology mixed up, but my goal is to avoid writing a framework to "hook up all the events" on an instance of an object, and use something like MEF to [Export] handlers (dependencies) that adhere to a very specific interface and [ImportMany] them into an object instance so my exports get called if the assemblies are there when the application starts. So maybe all of the objects could still be composed when the application starts, but I want the system to find and call all of them as the object is created and destroyed.

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  • Why friend function is preferred to member function for operator<<

    - by skydoor
    When you are going to print an object, a friend operator<< is used. Can we use member function for operator<< ? class A { public: void operator<<(ostream& i) { i<<"Member function";} friend ostream& operator<<(ostream& i, A& a) { i<<"operator<<"; return i;} }; int main () { A a; A b; A c; cout<<a<<b<<c<<endl; a<<cout; return 0; } One point is that friend function enable us to use it like this cout<<a<<b<<c What other reasons?

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  • Static member function pointer to hold non static member function

    - by user1425406
    This has defeated me. I want to have a static class variable which is a pointer to a (non-static) member function. I've tried all sorts of ways, but with no luck (including using typedefs, which just seemed to give me a different set of errors). In the code below I have the static class function pointer funcptr, and I can call it successfully from outside the class, but not from within the member function CallFuncptr - which is what I want to do. Any suggestions? #include <stdio.h> class A { public: static int (A::*funcptr)(); int Four() { return 4;}; int CallFuncptr() { return (this->*funcptr)(); } // doesn't link - undefined reference to `A::funcptr' }; int (A::*funcptr)() = &A::Four; int main() { A fred; printf("four? %d\n", (fred.*funcptr)()); // This works printf("four? %d\n", fred.CallFuncptr()); // But this is the way I want to call it }

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  • how are association, aggregation and composition written?

    - by ajsie
    i have read some posts about the differences between these 3 relationships and i think i get the point. i just wonder, are all these written the same when coding? question 1: all 3 are just a value of the object type in a instance variable? class A { public $b = '' public function __construct($object) { $this->b = $object // <-- could be a association, aggregation or a composition relation? } } question 2: does it have to be an instance variable or can it be a static one? class A { public static $b = '' // <-- nothing changed? public function __construct($object) { $this->b = $object } } question 3: is there a difference in where the object is created? i tend to think that composition object is created inside the object: class A { public $b = '' public function __construct() { $this->b = new Object // is created inside the object } } and aggregation/association is passed through a constructor or another method: class A { public $b = '' public function __construct($object) { // passed through a method $this->b = $object } } question 4: why/when is this important to know. do i have to comment an object inside another what relation its about or do you do it in an UML diagram? could someone shed a light on these questions. thanks!

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  • How To Pass Class As Params to Function

    - by Asim Sajjad
    How can I pass the Parameter to a function. for example public void GridViewColumns(params ClassName[] pinputparamter) { } and Class is as given below public Class ClassName { public string Name{get;set;} public int RecordID{get;set;} } can anyone has idea?

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  • jquery callback function

    - by kusanagi
    i use recaptcha Recaptcha.create("xxx", "recaptcha", { theme: 'clean', tabindex: 0, callback: $("#id").focus }); i want to use callback to focus some field, but it doesn't work, only callback: f works function f() { $("#FIO").focus(); } what is the problem?

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  • Calling matlab callback/function handle from Java

    - by jakob
    How do I pass a matlab function handle to a Java object and invoke it from within Java (that is, I want Java to tell matlab when it is ready with a calculation). I am trying to use the com.mathworks.jmi.Matlab class for evaluating Matlab expressions in the Java object, but I can't see how to 1) transfer the callback funcktion handle to Java, and 2) invoke it from Java possibly using the com.mathworks.jmi.Matlab class. Thanks, jakob

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  • PHP analog of mysql like function

    - by DCrystal
    Suppose it's a nub question, but is there an analog of mysql's LIKE function in php? So, e.g. : like('goo*','google.com');//is true like('*gl*','google.com');//true like('google.com','google.com')//also true I know regex rullez, but don't know any solution to reach this

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  • function overloading in C

    - by FL4SOF
    Is there any way to achieve function overloading in C? I am looking at simple functions to be overloaded like foo (int a) foo (char b) foo (float c , int d) I think there is no straight forward way, looking for workarounds if any?

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  • Get Date Strings for draw_calendar() Function

    - by Brandon
    I'm using the David Walsh PHP calendar script and need to format my date arguments like this: draw_calendar(7,2009); I want to get today's Month and Year as well as the next month and the month after that (so current month, plus one, plus one). How can I call the function three times in succession to generate these three calendars only knowing today's Month and Year? -Brandon

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  • MATLAB feature function

    - by yuk
    I'm curious where to find a complete description of FEATURE function? Which arguments it accepts? No documentation was found. I heard only about memstats and getpid. Anything else? >> which feature built-in (undocumented)

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  • Function overloading by return type?

    - by dsimcha
    Why don't more mainstream statically typed languages support function/method overloading by return type? I can't think of any that do. It seems no less useful or reasonable than supporting overload by parameter type. How come it's so much less popular?

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  • Registering a Named Function as a Listener with Jquery

    - by Marcus
    I'm new to javascript/jquery and I've done some poking around the web, but I can't figure out why the following is invalid: var toggleSection = function(sectionName) { // Do some Jquery work to toggle stuff based on sectionName string // (concatenate sectionName with other text to form selectors) }; $('#togglecont1').click(toggleSection("container1")); Is there something obvious I'm missing? Thanks in advance.

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  • How to store a function pointer in C#

    - by Joshua
    Let's say I want to store a group of function pointers in a List<(*func), and then later call them, perhaps even with parameters... Like if I stored in a Dict<(*func), object[] params could I call the func with the parameters? How would I do this?

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