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  • Simple to program yet computationally difficult functions

    - by ViralShah
    I need an example of a slow Excel sheet that could exist in the real world. Problem is I'm not sure what sort of functions are computationally difficult. Are there any sort of (maths?) functions that are easy enough to program that they can be used in Excel, yet computationally expensive? Something which has a real world application is a bonus.

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  • how to make functions global?

    - by fayer
    i'm trying to follow DRY and i've got some functions i have to reuse. i put them all as static functions in a class and want to use them in another class. what is the best way to make them available to a class. cause i can't extend the class, its already extended. should/could i use composition? what is best practice? thanks!

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  • What are the PHP "encryption" functions?

    - by Rob
    Looking for built in encryption functions, not to hide the string from the clever programmer, but instead just to obfuscate it a bit. Looking for functions such as str_rot13 and base64_encode, but I can't seem to locate any. Surely there are more?

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  • Frequent Functions: How to Structure?

    - by cam
    How should one structure their frequently used non-important functions (conversions, etc) in C# since everything must be contained in an object? Usually I take all these functions and put them in a static Utility class. Is this a good practice? How do most developers do it?

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  • Unable to execute functions on elements loaded with AJAX (jQuery)

    - by Jason
    i am using .prepend() to load data after i POST a form with .ajax(). once the new elements are added, my functions won't work on them. if i link the js file directly in the prepended data, the functions work, but when i POST, i starts multiplying the events. i have a feeling it has something to do with binding, but i am not able to figure out exactly how to handle it. any ideas? thanks!

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  • Loading dependencies for custom puppet functions

    - by Ben Smith
    I have written a custom puppet function, which is working fine, that depends on the cloudservers gem (a Rackspace client library). This is fine if I have pre-installed the gem on a server before running puppet but totally breaks if I have not installed the gem as the function seems to be run during the 'compilation' sweep, well before my package definition is realised. Here's what my .pp looks like, with get_hosts the function that requires the cloudservers gem. package { "rubygems": ensure => installed, provider => "gem"; } package { "cloudservers": ensure => installed, provider => "gem", require => Package["rubygems"]; } class hosts::us { $hosts = get_hosts("us") hostentry { $hosts: } } define hostentry() { $parts = split($name, ',') $address = $parts[0] $ip = $parts[1] $aliases = $parts[2] host{ $address: ip => $ip, host_aliases => $aliases } } Is there a way to stop the function getting run so early, or at least having it's run depend up the library being installed. Alternatively, is there a way that I can add dependencies somewhere in the functions folder that will be available to the function?

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  • Partial template specialization of free functions - best practices

    - by Poita_
    As most C++ programmers should know, partial template specialization of free functions is disallowed. For example, the following is illegal C++: template <class T, int N> T mul(const T& x) { return x * N; } template <class T> T mul<T, 0>(const T& x) { return T(0); } // error: function template partial specialization ‘mul<T, 0>’ is not allowed However, partial template specialization of classes/structs is allowed, and can be exploited to mimic the functionality of partial template specialization of free functions. For example, the target objective in the last example can be achieved by using: template <class T, int N> struct mul_impl { static T fun(const T& x) { return x * N; } }; template <class T> struct mul_impl<T, 0> { static T fun(const T& x) { return T(0); } }; template <class T, int N> T mul(const T& x) { return mul_impl<T, N>::fun(x); } It's more bulky and less concise, but it gets the job done -- and as far as users of mul are concerned, they get the desired partial specialization. My questions is: when writing templated free functions (that are intended to be used by others), should you automatically delegate the implementation to a static method function of a class, so that users of your library may implement partial specializations at will, or do you just write the templated function the normal way, and live with the fact that people won't be able to specialize them?

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  • Big-O of PHP functions?

    - by Kendall Hopkins
    After using PHP for a while now, I've noticed that not all PHP built in functions as fast as expected. Consider the below two possible implementations of a function that finds if a number is prime using a cached array of primes. //very slow for large $prime_array $prime_array = array( 2, 3, 5, 7, 11, 13, .... 104729, ... ); $result_array = array(); foreach( $array_of_number => $number ) { $result_array[$number] = in_array( $number, $large_prime_array ); } //still decent performance for large $prime_array $prime_array => array( 2 => NULL, 3 => NULL, 5 => NULL, 7 => NULL, 11 => NULL, 13 => NULL, .... 104729 => NULL, ... ); foreach( $array_of_number => $number ) { $result_array[$number] = array_key_exists( $number, $large_prime_array ); } This is because in_array is implemented with a linear search O(n) which will linearly slow down as $prime_array grows. Where the array_key_exists function is implemented with a hash lookup O(1) which will not slow down unless the hash table gets extremely populated (in which case it's only O(logn)). So far I've had to discover the big-O's via trial and error, and occasionally looking at the source code. Now for the question... I was wondering if there was a list of the theoretical (or practical) big O times for all* the PHP built in functions. *or at least the interesting ones For example find it very hard to predict what the big O of functions listed because the possible implementation depends on unknown core data structures of PHP: array_merge, array_merge_recursive, array_reverse, array_intersect, array_combine, str_replace (with array inputs), etc.

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  • DLL Exports: not all my functions are exported

    - by carmellose
    I'm trying to create a Windows DLL which exports a number of functions, howver all my functions are exported but one !! I can't figure it out. The macro I use is this simple one : __declspec(dllexport) void myfunction(); It works for all my functions except one. I've looked inside Dependency Walker and here they all are, except one. How can that be ? What would be the cause for that ? I'm stuck. Edit: to be more precise, here is the function in the .h : namespace my { namespace great { namespace namespaaace { __declspec(dllexport) void prob_dump(const char *filename, const double p[], int nx, const double Q[], const double xlow[], const char ixlow[], const double xupp[], const char ixupp[], const double A[], int my, const double bA[], const double C[], int mz, const double clow[], const char iclow[], const double cupp[], const char icupp[] ); }}} And in the .cpp file it goes like this: namespace my { namespace great { namespace namespaaace { namespace { void dump_mtx(std::ostream& ostr, const double *mtx, int rows, int cols, const char *ind = 0) { /* some random code there, nothing special, no statics whatsoever */ } } // end anonymous namespace here // dump the problem specification into a file void prob_dump( const char *filename, const double p[], int nx, const double Q[], const double xlow[], const char ixlow[], const double xupp[], const char ixupp[], const double A[], int my, const double bA[], const double C[], int mz, const double clow[], const char iclow[], const double cupp[], const char icupp[] ) { std::ofstream fout; fout.open(filename, std::ios::trunc); /* implementation there */ dump_mtx(fout, Q, nx, nx); } }}} Thanks

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  • How to call functions inside a C dll which take pointers as arguments from C#

    - by AndrejaKo
    Hi people, this is my first post here! I'm trying to make a windows forms program using C# which will use a precompiled C library. It will access a smart card and provide output from it. For the library, I have a .dll, .lib and .h and no source. In the .h file there are several structs defined. Most interesting functions of the .dll expect pointers to allocated structs as arguments. I've been calling functions inside the .dll like this: For example function EID_API int WINAPI EidStartup(int nApiVersion); would be called like this [DllImport("CelikApi.dll")]//the name of the .dll public static extern int EidStartup(int nApiVersion); Now my problem is that I can't find equivalent of C's pointers which point to dynamically allocated structures in memory in C#, so I don't know what to pass as argument to functions which take C pointers. I don't have much experience in C#, but to me its use looked as the easiest way of making the program I need. I tried with C++, but Visual Studio 2010 doesn't have IntelliSense for C++/CLR. If you can point me to something better, feel free to do so.

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  • pure/const functions in C++

    - by Albert
    Hi, I'm thinking of using pure/const functions more heavily in my C++ code. (pure/const attribute in GCC) However, I am curious how strict I should be about it and what could possibly break. The most obvious case are debug outputs (in whatever form, could be on cout, in some file or in some custom debug class). I probably will have a lot of functions, which don't have any side effects despite this sort of debug output. No matter if the debug output is made or not, this will absolutely have no effect on the rest of my application. Or another case I'm thinking of is the use of my own SmartPointer class. In debug mode, my SmartPointer class has some global register where it does some extra checks. If I use such an object in a pure/const function, it does have some slight side effects (in the sense that some memory probably will be different) which should not have any real side effects though (in the sense that the behaviour is in any way different). Similar also for mutexes and other stuff. I can think of many complex cases where it has some side effects (in the sense of that some memory will be different, maybe even some threads are created, some filesystem manipulation is made, etc) but has no computational difference (all those side effects could very well be left out and I would even prefer that). How does it work out in practice? If I mark such functions as pure/const, could it break anything (considering that the code is all correct)?

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  • C++: calling non-member functions with the same syntax of member ones

    - by peoro
    One thing I'd like to do in C++ is to call non-member functions with the same syntax you call member functions: class A { }; void f( A & this ) { /* ... */ } // ... A a; a.f(); // this is the same as f(a); Of course this could only work as long as f is not virtual (since it cannot appear in A's virtual table. f doesn't need to access A's non-public members. f doesn't conflict with a function declared in A (A::f). I'd like such a syntax because in my opinion it would be quite comfortable and would push good habits: calling str.strip() on a std::string (where strip is a function defined by the user) would sound a lot better than calling strip( str );. most of the times (always?) classes provide some member functions which don't require to be member (ie: are not virtual and don't use non-public members). This breaks encapsulation, but is the most practical thing to do (due to point 1). My question here is: what do you think of such feature? Do you think it would be something nice, or something that would introduce more issues than the ones it aims to solve? Could it make sense to propose such a feature to the next standard (the one after C++0x)? Of course this is just a brief description of this idea; it is not complete; we'd probably need to explicitly mark a function with a special keyword to let it work like this and many other stuff.

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  • Modify the server side functions using jquery

    - by ant
    Hi, I am developing one website using cakephp and jquery technologies. Server-side there are some functions which handles sql queris. As per requirement I want to modify server side functions on client side using jquery AJAX call. E.g. : Below is the function on server side to modify users information. function modifyUser(username,userid) { //update query statements } Then jquery AJAX call will be like this : $.ajax({ url: 'users/modiyUser', success: function() { alert("Updation done") or any statements. } }); and I want to modify above i.e. server side function depending upon client input criteria. $.ajax({ function users/modiyUser(username,userid) { // I will write here any other statements which gives me some other output. } }); Above AJAX call syntax may not present, but i think you all understood what I am trying to do I simply wants to modify/override server side functions on client side. Please let me know is there any way to resolve above mentioned requirement. Thanks in adavance

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  • Program to find the result of primitive recursive functions

    - by alphomega
    I'm writing a program to solve the result of primitive recursive functions: 1 --Basic functions------------------------------ 2 3 --Zero function 4 z :: Int -> Int 5 z = \_ -> 0 6 7 --Successor function 8 s :: Int -> Int 9 s = \x -> (x + 1) 10 11 --Identity/Projection function generator 12 idnm :: Int -> Int -> ([Int] -> Int) 13 idnm n m = \(x:xs) -> ((x:xs) !! (m-1)) 14 15 --Constructors-------------------------------- 16 17 --Composition constructor 18 cn :: ([Int] -> Int) -> [([Int] -> Int)] -> ([Int] -> Int) 19 cn f [] = \(x:xs) -> f 20 cn f (g:gs) = \(x:xs) -> (cn (f (g (x:xs))) gs) these functions and constructors are defined here: http://en.wikipedia.org/wiki/Primitive_recursive_function The issue is with my attempt to create the compositon constructor, cn. When it gets to the base case, f is no longer a partial application, but a result of the function. Yet the function expects a function as the first argument. How can I deal with this problem? Thanks.

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  • gcc -finline-functions behaviour?

    - by user176168
    I'm using gcc with the -finline-functions optimization for release builds. In order to combat code bloat because I work on an embedded system I want to say don't inline particular functions. The obvious way to do this would be through function attributes ie attribute(noinline). The problem is this doesn't seem to work when I switch on the global -finline-functions optimisation which is part of the -O3 switch. It also has something to do with it being templated as a non templated version of the same function doesn't get inlined which is as expected. Has anybody any idea of how to control inlining when this global switch is on? Here's the code: #include <cstdlib> #include <iostream> using namespace std; class Base { public: template<typename _Type_> static _Type_ fooT( _Type_ x, _Type_ y ) __attribute__ (( noinline )); }; template<typename _Type_> _Type_ Base::fooT( _Type_ x, _Type_ y ) { asm(""); return x + y; } int main(int argc, char *argv[]) { int test = Base::fooT( 1, 2 ); printf( "test = %d\n", test ); system("PAUSE"); return EXIT_SUCCESS; }

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  • Using ms: xpath functions inside XPathExpression

    - by Filini
    I am trying to use Microsoft XPath Extension Functions (such as ms:string-compare http://msdn.microsoft.com/en-us/library/ms256114.aspx) inside an XPathExpression object. These functions are extensions inside the MSXML library, and if I use them in an XslCompiledTransform (simply adding the "ms" namespace) they work like a charm: var xsl = @" <?xml version=""1.0"" encoding=""UTF-8""?> <xsl:stylesheet version=""2.0"" xmlns:xsl=""http://www.w3.org/1999/XSL/Transform"" xmlns:xs=""http://www.w3.org/2001/XMLSchema"" xmlns:fn=""http://www.w3.org/2005/xpath-functions"" xmlns:ms=""urn:schemas-microsoft-com:xslt""> <xsl:output method=""xml"" version=""1.0"" encoding=""UTF-8"" indent=""yes""/> <xsl:template match=""/Data""> <xsl:element name=""Result""> <xsl:value-of select=""ms:string-compare(@timeout1, @timeout2)""/> </xsl:element> </xsl:template> </xsl:stylesheet>"; var xslDocument = new XmlDocument(); xslDocument.LoadXml(xsl); var transform = new XslCompiledTransform(); transform.Load(xslDocument); Then I tried using them in an XPathExpression: XPathNavigator nav = document.DocumentElement.CreateNavigator(); XPathExpression expr = nav.Compile("ms:string-compare(/Data/@timeout1, /Data/@timeout2)"); XmlNamespaceManager manager = new XmlNamespaceManager(document.NameTable); manager.AddNamespace("ms", "urn:schemas-microsoft-com:xslt"); expr.SetContext(manager); nav.Evaluate(expr); But I get an exception "XsltContext is needed for this query because of an unknown function". XsltContext is a specific XmlNamespaceManager, but I don't know if it's possible to instantiate it without an actual XslCompiledTransform (it's abstract) and use it as my expression context. Is there any way to do this (or any other way to use ms: extensions inside an XPathExpression)?

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  • List of Big-O for PHP functions?

    - by Kendall Hopkins
    After using PHP for a while now, I've noticed that not all PHP built in functions as fast as expected. Consider the below two possible implementations of a function that finds if a number is prime using a cached array of primes. //very slow for large $prime_array $prime_array = array( 2, 3, 5, 7, 11, 13, .... 104729, ... ); $result_array = array(); foreach( $array_of_number => $number ) { $result_array[$number] = in_array( $number, $large_prime_array ); } //still decent performance for large $prime_array $prime_array => array( 2 => NULL, 3 => NULL, 5 => NULL, 7 => NULL, 11 => NULL, 13 => NULL, .... 104729 => NULL, ... ); foreach( $array_of_number => $number ) { $result_array[$number] = array_key_exists( $number, $large_prime_array ); } This is because in_array is implemented with a linear search O(n) which will linearly slow down as $prime_array grows. Where the array_key_exists function is implemented with a hash lookup O(1) which will not slow down unless the hash table gets extremely populated (in which case it's only O(logn)). So far I've had to discover the big-O's via trial and error, and occasionally looking at the source code. Now for the question... I was wondering if there was a list of the theoretical (or practical) big O times for all* the PHP built in functions. *or at least the interesting ones For example find it very hard to predict what the big O of functions listed because the possible implementation depends on unknown core data structures of PHP: array_merge, array_merge_recursive, array_reverse, array_intersect, array_combine, str_replace (with array inputs), etc.

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  • Very simple python functions takes spends long time in function and not subfunctions

    - by John Salvatier
    I have spent many hours trying to figure what is going on here. The function 'grad_logp' in the code below is called many times in my program, and cProfile and runsnakerun the visualize the results reveals that the function grad_logp spends about .00004s 'locally' every call not in any functions it calls and the function 'n' spends about .00006s locally every call. Together these two times make up about 30% of program time that I care about. It doesn't seem like this is function overhead as other python functions spend far less time 'locally' and merging 'grad_logp' and 'n' does not make my program faster, but the operations that these two functions do seem rather trivial. Does anyone have any suggestions on what might be happening? Have I done something obviously inefficient? Am I misunderstanding how cProfile works? def grad_logp(self, variable, calculation_set ): p = params(self.p,self.parents) return self.n(variable, self.p) def n (self, variable, p ): gradient = self.gg(variable, p) return np.reshape(gradient, np.shape(variable.value)) def gg(self, variable, p): if variable is self: gradient = self._grad_logps['x']( x = self.value, **p) else: gradient = __builtin__.sum([self._pgradient(variable, parameter, value, p) for parameter, value in self.parents.iteritems()]) return gradient

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  • Javascript cloned object looses its prototype functions

    - by Jake M
    I am attempting to clone an object in Javascript. I have made my own 'class' that has prototype functions. My Problem: When I clone an object, the clone cant access/call any prototype functions. I get an error when I go to access a prototype function of the clone: clone.render is not a function Can you tell me how I can clone an object and keep its prototype functions This simple JSFiddle demonstrates the error I get: http://jsfiddle.net/VHEFb/1/ function cloneObject(obj) { // Handle the 3 simple types, and null or undefined if (null == obj || "object" != typeof obj) return obj; // Handle Date if (obj instanceof Date) { var copy = new Date(); copy.setTime(obj.getTime()); return copy; } // Handle Array if (obj instanceof Array) { var copy = []; for (var i = 0, len = obj.length; i < len; ++i) { copy[i] = cloneObject(obj[i]); } return copy; } // Handle Object if (obj instanceof Object) { var copy = {}; for (var attr in obj) { if (obj.hasOwnProperty(attr)) copy[attr] = cloneObject(obj[attr]); } return copy; } throw new Error("Unable to copy obj! Its type isn't supported."); } function MyObject(name) { this.name = name; // I have arrays stored in this object also so a simple cloneNode(true) call wont copy those // thus the need for the function cloneObject(); } MyObject.prototype.render = function() { alert("Render executing: "+this.name); } var base = new MyObject("base"); var clone = cloneObject(base); clone.name = "clone"; base.render(); clone.render(); // Error here: "clone.render is not a function"

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  • How do I write recursive anonymous functions?

    - by James T Kirk
    In my continued effort to learn scala, I'm working through 'Scala by example' by Odersky and on the chapter on first class functions, the section on anonymous function avoids a situation of recursive anonymous function. I have a solution that seems to work. I'm curious if there is a better answer out there. From the pdf: Code to showcase higher order functions def sum(f: Int => Int, a: Int, b: Int): Int = if (a > b) 0 else f(a) + sum(f, a + 1, b) def id(x: Int): Int = x def square(x: Int): Int = x * x def powerOfTwo(x: Int): Int = if (x == 0) 1 else 2 * powerOfTwo(x-1) def sumInts(a: Int, b: Int): Int = sum(id, a, b) def sumSquares(a: Int, b: Int): Int = sum(square, a, b) def sumPowersOfTwo(a: Int, b: Int): Int = sum(powerOfTwo, a, b) scala> sumPowersOfTwo(2,3) res0: Int = 12 from the pdf: Code to showcase anonymous functions def sum(f: Int => Int, a: Int, b: Int): Int = if (a > b) 0 else f(a) + sum(f, a + 1, b) def sumInts(a: Int, b: Int): Int = sum((x: Int) => x, a, b) def sumSquares(a: Int, b: Int): Int = sum((x: Int) => x * x, a, b) // no sumPowersOfTwo My code: def sumPowersOfTwo(a: Int, b: Int): Int = sum((x: Int) => { def f(y:Int):Int = if (y==0) 1 else 2 * f(y-1); f(x) }, a, b) scala> sumPowersOfTwo(2,3) res0: Int = 12

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  • C: writing the following code into functions

    - by donok
    Dear respected programmers. Please could you help me (again) on how to put the following code into functions for my program. I have read on-line and understand how functions work but when I do it myself it all goes pear shaped/wrong(I am such a noob). Please could you help with how to for example to write the code below into functions.(like opening the input file). My attempt: void outputFile(int argc, char **argv) { /* Check that the output file doesnt exist */ if (stat(argv[argc-1], &inode) != -1) { printf("Warning: The file %s already exists. Not going to overwrite\n", argv[argc-1]); return -1; } /*Opening ouput files*/ file_desc_out = open(argv[i],O_CREAT | O_WRONLY | O_EXCL , S_IRUSR|S_IWUSR); if(file_desc_out == -1) { printf("Error: %s cannot be opened. \n",argv[i]); //insted of argv[2] have pointer i. return -1; } } Any help on how I would now reference to this in my program is appreciated thank you. I tried: ouputfile(but I cant figure out what goes here and why either).

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  • Extracting exported functions out of a shared lib (ubuntu)

    - by Pingu
    the title already describes my problem. I found this post, but it didn't completely answers my question. With the help of it i got this output from nm... $nm -C -g -D ./libLoggingHandler.so 000000cc A _DYNAMIC ... 000042e0 T write_str(char*, char const*, int*) 00005a78 T RingBuffer::WriteUnlock() ... 00005918 T TraceLines::GetItemSize() ... U SharedMemory::attach(int, void const*, int) ... 00003810 T TraceProfile::FindLineNr(int, int) ... 00002d40 T LoggingHandler::getLogLevel() ... U SharedResource::getSharedResourceKey(char const*, int) ... which are the exported functions? I already found a hint in this post, that the "T" indicates that its getting exported. But if i check the nm manual here, it just says T - The symbol is in the text (code) section. My questions is: Does this output give me the information which functions are exported functions (or variables)? If not, how do i get it? Greetings, Pingu

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  • How do you chain functions dynamically in jQuery?

    - by clarke78
    I want to loop through an object that contains functions which will execute one after another. My most ideal approach would be to have these chain somehow (ie. func2 waits for func1 and func3 waits for func2) but this needs to happen dynamically and the functions will all have different durations. I'm using jQuery so I thought that perhaps "queue()" may help but I haven't worked with it much. A main concern is to not add any scope/callbacks to the functions within the object. I'd rather somehow enclose them within a parent function to execute within the loop in order to create the callback/chaining. Here's an example of what I've got now, but dumbed down. Thanks for any help! var obj = [ {'name':'func1','callback':function(){ alert(1); }}, {'name':'func2','callback':function(){ alert(2); }}, {'name':'func3','callback':function(){ alert(3); }} ]; $.each(obj, function(x, el) { el.callback(); });

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  • Calling multiple functions simultaneously with jquery.

    - by clarke78
    I want to loop through an object that contains functions which will execute one after another. My most ideal approach would be to have these chain somehow (ie. func2 waits for func1 and func3 waits for func2) but this needs to happen dynamically and the functions will all have different durations. I'm using jQuery so I thought that perhaps "queue()" may help but I haven't worked with it much. A main concern is to not add any scope/callbacks to the functions within the object. I'd rather somehow enclose them within a parent function to execute within the loop in order to create the callback/chaining. Here's an example of what I've got now, but dumbed down. Thanks for any help! var obj = [ {'name':'func1','callback':function(){ alert(1); }}, {'name':'func2','callback':function(){ alert(2); }}, {'name':'func3','callback':function(){ alert(3); }} ]; $.each(obj, function(x, el) { el.callback(); });

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