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  • Operators vs Functions in C/C++

    - by user356106
    Someone recently asked me the difference between a C++ standard operator (e.g. new,delete,sizeof) and function (e.g. tan,delete, malloc). By "standard" I mean those provided by default by the compiler suite, and not user defined. Below were the answers I gave, though neither seemed satisfactory. (1) An operator doesn't need any headers to be included to use it : E.g. you can have a call to new without including any headers. However, a function (say free() ) does need headers included, compulsorily. (2) An operator is defined as such (ie as a class operator) somewhere in the standard headers. A function isn't. Can you critique these answers and give me a better idea of the difference?

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  • using ajax url to call function

    - by Steven Vanerp
    Hopefully I can ask this correctly cuz I know what I want it to do but can't seem to find any answers from searching. I have a func.php page where I have all my functions and I want ajax to use one function from that page. func.php function toptable() { echo"something happens in here"; } index.php <?php include 'func.php'; ?> <script type="text/javascript"> function check_username() { uname=document.getElementById("username").value; var params = "user_id="+uname; var url = "topoftable()"; $.ajax({ type: 'POST', url: url, dataType: 'html', data: params, beforeSend: function() { document.getElementById("right").innerHTML= 'checking' ; }, complete: function() { }, success: function(html) { document.getElementById("right").innerHTML= html ; } }); } </script> Make sense?

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  • What is the best way to identify that a function returned and automatically do something with it?

    - by EpsilonVector
    I'm implementing user threads on a Linux 2.4 kernel (homework) and my threads are basically just functions running with their own execution context (for example: uthread_create(functionpointer, args)). I'm having a hard time figuring out how to catch the return value and have it ready to be returned when two threads join. I know where to get the value from (eax), but not how to identify that the function actually finished. There's something called atexit, but I've seen people advising against using it, so... what is the best way to discover that a function returned and do something about it?

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  • do you call them functions, procedures or methods?

    - by lowlyintern
    consider a standard c# 'function' public void foo() { //some code } In c or c++ this is called a 'function' - even if taking no parameters and returning no value. In another language maybe it would be a 'procedure'. In object orientation speak it would be called a 'method' if a class member. What would be the correct term to use in c#?

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  • from JS to iphone dev - what's the best language to start with?

    - by Enkai
    I am a total beginner and would like to eventually learn to develop for the iphone. I have just done a beginner's CS course where the language we learned was JavaScript. We studied basic concepts like: variables, arrays, loops (for,while,if,if..else..), properties and functions. I'm wondering if I am starting in the right/wrong place by following this book: Learn C on the Mac by Dave Mark? I have read a few chapters and am finding it a bit hard to get my head around the way that C works, for example the way that Strings are printed seems overly complicated as compared to JS. Do you think that JS was the wrong language to start off with and would I be better to go from JS straight to Objective-C rather than to C? I have tried to read up on previous threads on the merits/demerits of learning C first but haven't found any that relate JS to learning C/Obj C/ Cocoa. Any advice appreciated as I am very new to this. Thanks

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  • error_expected_primary expression before in. In functions

    - by user2975402
    Here is my code. I try to fix it and I always obtain the same error: expected primary expression before 'int'. in line 47, 55, 63, 80, 86. And I've already tried this program in small pieces before and it works. It doesn't marked that error. ` #include using namespace std; int add (int a, int b) { int r; r=a+b; return (r); } int ssub (int a, int b) { int r; r=a-b; return (r); } int mult(int a, int b) { int r; r=a*b; return (r); } int menu(int a, int b){ int r; char x; cout <<"What do you want to do: \na.Adding \n s. Substract \n m. Multiply. \n. e. Exit"<<endl; cin>>x; switch (x){ case 'a': cout << "Give a value for a"<<endl; cin>>a; cout <<"Give a value for b"<<endl; cin>>b; add (int a, int b); //aquí y en otras líneas me sale: expected primary expression before int. break; case 's': cout << "Give a value for a"<<endl; cin>>a; cout <<"Give a value for b"<<endl; cin>>b; ssub (int a, int b); break; case 'm': cout << "Give a value for a"<<endl; cin>>a; cout <<"Give a value for b"<<endl; cin>>b; mult (int a, int b); break; case 'e': x='e'; break; default: cout<<"Wrong choice. Run the program again and choose another letter"<<endl; break; } return r; } cout<<"The result is " << menu (int a, int b)<<endl; int main() { menu (int a, int b); return 0; } `

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  • Dynamically udpate canvasOverlay property of jQuery jqPlot

    - by You Kuper
    I want to dynamically udpate canvasOverlay property of jQuery jqPlot. This will provide the effect of a timeline in my jqPlot. This effect should be similar to the one shown in this jFiddle. However, instead of drawing points, I want to update canvasOverlay property every second: canvasOverlay: { show: true, objects: [ { rectangle: { xmax: new Date(), xminOffset: "0px", xmaxOffset: "0px", yminOffset: "0px", ymaxOffset: "0px", color: "rgba(0, 0, 0, 0.1)", showTooltip: true } }, ] } How can I do this? What are the functions I should use? UPDATE: My idea is to do something like this: canvasOverlay: { name: 'current', show: true, objects: [ { rectangle: { xmax: new Date(), xminOffset: "0px", xmaxOffset: "0px", yminOffset: "0px", ymaxOffset: "0px", color: "rgba(0, 0, 0, 0.1)", showTooltip: true } }, ] } /... var co = plot.plugins.canvasOverlay; var current = co.get('current'); current.options.objects.rectangle.xmax = new Date(); co.draw(plot);

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  • Templates, interfaces (multiple inheritance) and static functions (named constructors)

    - by fledgling Cxx user
    Setup I have a graph library where I am trying to decompose things as much as possible, and the cleanest way to describe it that I found is the following: there is a vanilla type node implementing only a list of edges: class node { public: int* edges; int edge_count; }; Then, I would like to be able to add interfaces to this whole mix, like so: template <class T> class node_weight { public: T weight; }; template <class T> class node_position { public: T x; T y; }; and so on. Then, the actual graph class comes in, which is templated on the actual type of node: template <class node_T> class graph { protected: node_T* nodes; public: static graph cartesian(int n, int m) { graph r; r.nodes = new node_T[n * m]; return r; } }; The twist is that it has named constructors which construct some special graphs, like a Cartesian lattice. In this case, I would like to be able to add some extra information into the graph, depending on what interfaces are implemented by node_T. What would be the best way to accomplish this? Possible solution I thought of the following humble solution, through dynamic_cast<>: template <class node_T, class weight_T, class position_T> class graph { protected: node_T* nodes; public: static graph cartesian(int n, int m) { graph r; r.nodes = new node_T[n * m]; if (dynamic_cast<node_weight<weight_T>>(r.nodes[0]) != nullptr) { // do stuff knowing you can add weights } if (dynamic_cast<node_position<positionT>>(r.nodes[0]) != nullptr) { // do stuff knowing you can set position } return r; } }; which would operate on node_T being the following: template <class weight_T, class position_T> class node_weight_position : public node, public node_weight<weight_T>, public node_position<position_T> { // ... }; Questions Is this -- philosophically -- the right way to go? I know people don't look nicely at multiple inheritance, though with "interfaces" like these it should all be fine. There are unfortunately problems with this. From what I know at least, dynamic_cast<> involves quite a bit of run-time overhead. Hence, I run into a problem with what I had solved earlier: writing graph algorithms that require weights independently of whether the actual node_T class has weights or not. The solution with this 'interface' approach would be to write a function: template <class node_T, class weight_T> inline weight_T get_weight(node_T const & n) { if (dynamic_cast<node_weight<weight_T>>(n) != nullptr) { return dynamic_cast<node_weight<weight_T>>(n).weight; } return T(1); } but the issue with it is that it works using run-time information (dynamic_cast), yet in principle I would like to decide it at compile-time and thus make the code more efficient. If there is a different solution that would solve both problems, especially a cleaner and better one than what I have, I would love to hear about it!

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  • Unit testing a functions whose purposes is side effects

    - by David
    How would you unit test do_int_to_string_conversion? #include <string> #include <iostream> void do_int_to_string_conversion(int i, std::string& s) { switch(i) { case 1: s="1"; break; case 2: s="2"; break; default: s ="Nix"; } std::cout << s << "\n"; } int main(int argc, char** argv){ std::string little_s; do_int_to_string_conversion(1, little_s); do_int_to_string_conversion(2, little_s); do_int_to_string_conversion(3, little_s); }

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  • c Pointer to pointer, or passing list to functions

    - by user361808
    Hi, I am new to c programming. Could anyone please tell me what's wrong with the following program? typedef struct Person_s { int age; char name[40]; } Person_t; int process_list(int *countReturned, Person_t **p_list) { Person_t *rowPtr=0; //the actual program will fethc data from DB int count =1; if(!((*p_list) = (Person_t *) malloc(sizeof(Person_t)))) { return -1; } rowPtr = *p_list; rowPtr[count-1].age =19; strcpy(rowPtr[count-1].name,"Prince Dastan"); *countReturned = count; return 0; } int main(int argc, char *argv[]) { Person_t *tmpPerson=0; Person_t **p_list=0; int *count=0; int i; process_list(count,p_list); tmpPerson = *p_list; for(i=0; i< *count; i++) { printf("Name: %s , age: %d\n",tmpPerson->name,tmpPerson->age); tmpPerson++; } //free(tmpPerson); return 0; }

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  • Why does the assignment operator return a value and not a reference?

    - by Nick Lowman
    I saw the example below explained on this site and thought both answers would be 20 and not the 10 that is returned. He wrote that both the comma and assignment returns a value, not a reference. I don't quite understand what that means. I understand it in relation to passing variables into functions or methods i.e primitive types are passed in by value and objects by reference but I'm not sure how it applies in this case. I also understand about context and the value of 'this' (after help from stackoverflow) but I thought in both cases I would still be invoking it as a method, foo.bar() which would mean foo is the context but it seems both result in a function call bar(). Why is that and what does it all mean? var x = 10; var foo = { x: 20, bar: function () {return this.x;} }; (foo.bar = foo.bar)();//returns 10 (foo.bar, foo.bar)();//returns 10

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  • What is the precedence of characters when sorting in MySQL, PHP, or just in general?

    - by FireCoding
    Question: Where can I find the precedence of characters when sorting in MySQL, PHP, or just in general on Linux and Windows OS? For example, everybody knows that a comes before b when performing an ascending sort on a string in MySQL. But what about other characters? Does the dollar-sign $ come before asterisk * ? Does a space come before an exclamation-mark? etc... What dictates the sort order? Does it use underlying ascii / UTF-8 values? Is it different for different technologies? Technologies to consider: Databases - MySQL / SQL / SQLite / Oracle / etc Programming languages (for string-sorting functions) - PHP / Javascript / ASP.NET / Visual C# / Python / Ruby / Objective C OS (i.e., sorting files by filename) - Windows / Linux / MacOS / iOS / Android

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  • Call inner function of jQuery-Plugin-function?

    - by faileN
    Hello Everyone, I've written an jQuery-Plugin, which I want to use as Object. So I declared some functions within the plugin, which I want to call from any other location, just like an object with methods. Is that even possible? To keep it simple: (function( $ ){ $.fn.myPlugin = function(){ // Here I want methods... function foo() { // do something... } } })(jQuery); Then I want to call the inner function from outside the plugin like: $.myPlugin.foo(); But that doesn't seem to work. So is it even possible? Or are there any other solutions? I don't want to use an normal unrelated jQuery-Class for this purpose. Because this plugin should work together with some other jQuery-Plugins. Thank you

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  • Difference between macros and functions in C in relation to instruction memory and speed

    - by DAHANS
    To my understanding the difference between a macro and a function is, that a macro-call will be replaced by the instruction in the definition, and a function does the whole push, branch and pop -thing. Is this right, or have I understand something wrong? Additionally, if this is right, it would mean, that macros would take more space, but would be faster (because of the lack of the push,branch and pop instructions.), wouldn't it?

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  • Basic string and value functions in Objective-C for iPhone

    - by David Maitland
    I have very little programming knowledge; only a fair bit in Visual Basic. How do I take a value from a text field, then do some simple math such as divide the value by two, then display it back to the user in the same field? In Visual Basic you could just do txtBoxOne.text = txtBoxOne.text / 2 I understand this question is more than one question and is very basic stuff, but I need to get my head out of Visual Basic and into where I should be :)

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  • C/C++ definitions of functions

    - by Vit
    Yesterday, I have been watching discussion here, about compilers and linkers. It was about C library function definitions. I have never thought of that, so it inspired me to do some searching, but I cannot find exactly what I want. I wonder, what is the smallest syntax you need to add into your source code to enable just printf() function. I mean the function declaration from stdio.h you need.

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  • More compact way to do this?

    - by Macha
    I have a couple of functions that loop around the surrounding cells of a cell. The grid is contained inside an array. In my code, I have checks to make sure it's not one of the edge cells, as checking an undefined cell causes an error. As such, I have code like this: if(x > 0) { var firstX = x - 1; } else { var firstX = x; } if(x < 199) { var lastX = x + 1; } else { var lastX = x; } if(y > 0) { var firstY = y - 1; } else { var firstY = y; } if(y < 199) { var lastY = y + 1; } else { var lastY = y; } A lot of lines of code to do very little. Is there a more elegant way to do this?

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  • Calling member functions dynamically

    - by user652511
    I'm pretty sure it's possible to call a class and its member function dynamically in Delphi, but I can't quite seem to make it work. What am I missing? // Here's a list of classes (some code removed for clarity) moClassList : TList; moClassList.Add( TClassA ); moClassList.Add( TClassB ); // Here is where I want to call an object's member function if the // object's class is in the list: for i := 0 to moClassList.Count - 1 do if oObject is TClass(moClassList[i]) then with oObject as TClass(moClassList[i]) do Foo(); I get an undeclared identifier for Foo() at compile. Clarification/Additional Information: What I'm trying to accomplish is to create a Change Notification system between business classes. Class A registers to be notified of changes in Class B, and the system stores a mapping of Class A - Class B. Then, when a Class B object changes, the system will call a A.Foo() to process the change. I'd like the notification system to not require any hard-coded classes if possible. There will always be a Foo() for any class that registers for notification. Maybe this can't be done or there's a completely different and better approach to my problem. By the way, this is not exactly an "Observer" design pattern because it's not dealing with objects in memory. Managing changes between related persistent data seems like a standard problem to be solved, but I've not found very much discussion about it. Again, any assistance would be greatly appreciated. Jeff

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  • "javascript: void(0)" links sometimes break event handlers in internet explorer

    - by internet man
    A while back I ran in to a problem where after clicking an anchor with "javascript: void(0)" events just stopped firing. I read that following a link puts the page in a different state and in that different state events don't fire. Even though the link is not real, it sometimes confuses IE. Anyway, I removed the "javascript: void(0)"'s and the problem has not been seen again. Now, in a different application I am seeing the same thing... kinda. Clicking the "javascript: void(0)" sometimes has no ill effect. But then for some reason or another after clicking the bad link the page will stop working. Once this happens it will continue to happen consistently until the client machine is rebooted. After reboot, you are back to it sometimes happening. Crazy right? Reboot fixing a web page!?!?! So, my question is has anyone seen this before? Can anyone give an explanation for this issue? Any documentation on this issue? I can't seem to find anything on it again. Does this even make sense? I already know "javascript: void(0)" is bad practice... I am just looking to understand the issue. Specifically, this is IE7. Thanks for reading!

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  • JQuery create new select option

    - by nav
    Hi I have the below functions in regular javascript creating select options. Is there a way I can do this with JQuery without having to use the form object? function populate(form) { form.options.length = 0; form.options[0] = new Option("Select a city / town in Sweden",""); form.options[1] = new Option("Melbourne","Melbourne"); } Below is how I call the function above: populate(document.form.county); //county is the id of the dropdownlist to populate. Many Thanks,

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  • function to profile / performance test PHP functions?

    - by Haroldo
    I'm not experiencing any performance issues, however I'd like to take a look at what takes how long and how much memory cpu it uses etc. I'd like to get a firsthand understanding of which things can be bottle necks etc and improve any code i might reuse or build upon... (perfectionist) I'm looking to create a litte function that i can call at the begining and end of each function that records: execution time memory used cpu demand any ideas?

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  • Are there inline functions in java?

    - by giri
    There is any concept of inline function or its replaced by some other things in java..if yes then how we use it..because i'v heard that public, static and final methods are the inline function.can we create our own inline function?

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