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  • Problem separating C++ code in header, inline functions and code.

    - by YuppieNetworking
    Hello all, I have the simplest code that I want to separate in three files: Header file: class and struct declarations. No implementations at all. Inline functions file: implementation of inline methods in header. Code file: normal C++ code for more complicated implementations. When I was about to implement an operator[] method, I couldn't manage to compile it. Here is a minimal example that shows the same problem: Header (myclass.h): #ifndef _MYCLASS_H_ #define _MYCLASS_H_ class MyClass { public: MyClass(const int n); virtual ~MyClass(); double& operator[](const int i); double operator[](const int i) const; void someBigMethod(); private: double* arr; }; #endif /* _MYCLASS_H_ */ Inline functions (myclass-inl.h): #include "myclass.h" inline double& MyClass::operator[](const int i) { return arr[i]; } inline double MyClass::operator[](const int i) const { return arr[i]; } Code (myclass.cpp): #include "myclass.h" #include "myclass-inl.h" #include <iostream> inline MyClass::MyClass(const int n) { arr = new double[n]; } inline MyClass::~MyClass() { delete[] arr; } void MyClass::someBigMethod() { std::cout << "Hello big method that is not inlined" << std::endl; } And finally, a main to test it all: #include "myclass.h" #include <iostream> using namespace std; int main(int argc, char *argv[]) { MyClass m(123); double x = m[1]; m[1] = 1234; cout << "m[1]=" << m[1] << endl; x = x + 1; return 0; } void nothing() { cout << "hello world" << endl; } When I compile it, it says: main.cpp:(.text+0x1b): undefined reference to 'MyClass::MyClass(int)' main.cpp:(.text+0x2f): undefined reference to 'MyClass::operator[](int)' main.cpp:(.text+0x49): undefined reference to 'MyClass::operator[](int)' main.cpp:(.text+0x65): undefined reference to 'MyClass::operator[](int)' However, when I move the main method to the MyClass.cpp file, it works. Could you guys help me spot the problem? Thank you.

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  • Is it possible to set a default behaviour for custom (non-native) methods/functions in Java?

    - by Tom
    Is it possible to set a default behaviour for custom (non-native) methods/functions in Java? For example, I would like to change the default "Function" to do a System.out.println("message") whenever called. So, when a custom method/function is being created: public String testMethod() { //custom code } it should execute the newly added default behaviour (in this case the system output), before the custom code is run. Even if this would be a bad excercise, is it possible? Maybe by extending the function class or something?

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  • Calling all the 3 functions while using or operator even after returning true as a result.

    - by Shantanu Gupta
    I am calling three functions in my code where i want to validate some of my fields. When I tries to work with the code given below. It checks only for first value until it gets false result. I want some thing like that if fisrt function returns true then it should also call next function and so on. What can be used instead of Or Operator to do this. if (IsFieldEmpty(ref txtFactoryName, true, "Required") || IsFieldEmpty(ref txtShortName, true, "Required") || IsFieldEmpty(ref cboGodown, true, "Required")) { }

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  • How do I call functions inside c++ dll from lua?

    - by Brian T Hannan
    I have a dll written in C++ that is legacy code and cannot modify the source code. I want to be able to call some of the functions inside of the dll from lua. For example, I'd like to do something like this: -- My Lua File include(myCppDll.dll) function callCppFunctionFromDll() local result = myCppFunctionFromDll(arg1, arg2) --Do something with result here end Is something like this possible?

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  • Static variables within functions in C++ - allocated even if function doesn't run?

    - by John C
    I've been reading up on C++ on the Internet, and here's one thing that I haven't been quite able to find an answer to. I know that static variables used within functions are akin to globals, and that subsequent invocations of that function will have the static variable retain its value between calls. However, if the function is never claled, does the static variable get allocated? Thanks

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  • Using "null" in jQuery functions. Is this okay?

    - by Nick
    My database consists of some entries which are NULL (so they don't affect max, min, etc..). When I pull all of the data from the database, I need to repopulate form fields with the values. Using .val(value) where value = NULL seems to work without any problems, but I'm not sure if this is a valid way to go about this. It doesn't say anything in the jQuery documentation (that I can find) about using NULL as parameters to functions.

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  • Am I trying to Implement Multiple Inheritance. How can I do this.

    - by Shantanu Gupta
    I have created a class say A which has some functions defined as protected. Now Class B inherits A and class C inherits B. Class A has private default constructor and protected parameterized constructor. I want Class B to be able to access all the protected functions defined in Class A but class C can have access on some of the functions only not all the functions and class C is inheriting class B. How can I restrict access to some of the functions of Class A from Class C ? EDIT: namespace Db { public Class A { private A(){} protected A(string con){assign this value} protected DataTable getTable(){return Table;} protected Sqlparameters setParameters(){return parameter;} } } namespace Data { public Class B:A { protected B():base("constring"){} protected DataTable output(){return getTable();} protected sqlparameter values(param IDataParameter[] parameter){} } } namespace Bsns { public Class C:B { protected C():base(){} protected DataTable show() {return values(setparameter());} } } EDIT I think what I am trying to do here is Multiple inheritance. Please check. Class A { //suppose 10 functions are declared } Class B:A { //5 functions declared which are using A's function in internal body } Class C:B { //using all functions of B but require only 4 functions of A to be accessible by C. }

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  • What php programmer should know?

    - by emchinee
    I've dig the database here and didn't found any answer for my question. What is a standard for a php programmer to know? I mean, literally, what group of language functions, mechanisms, variables should person know to consider oneself a (good) php programmer? (I know 'being good' is beyond language syntax, still I'm considering syntax of plain php only) To give an example what I mean: functions to control http sessions, cookies functions to control connection with databases functions to control file handling functions to control xml etc.. I omit phrases like 'security' or 'patterns' or 'framework' intentionally as it applies to every programming language. Hope I made myself clear, any input appreciated :) Note: Michael J.V. is right claiming that databases are independent from language, so to put my question more precisely and emphasise differences: Practises or security, are some ideas to implement (there is no 'Pattern' object with 'Decorator()' method, is there?) while using databases means knowing a mysqli and a set of its methods.

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  • What are the use cases for closures/callback functions in Javascript?

    - by Christopher Altman
    I was listening to Crockford's talk on Javascript closures and am convinced of the benefit of information hiding, but I do not have a firm understanding of when to use callback functions. It is mostly a true statement that a person could accomplish the same functionality with or without callbacks. As someone who is writing code, what heuristics or cues should I keep in mind when determining when to use callbacks/closures? I am not looking for the blanket statement 'Closures make more secure code', rather a list of practical examples or rules of thumb for when callbacks are the right idea. Crockford's Presentation: http://www.yuiblog.com/blog/2010/04/08/video-crockonjs-5/

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  • What is the relationship between recursion functions and memory stack?

    - by Eslam
    is there's a direct relationship between recursive functions and the memory stack, for more explanation consider that code: public static int triangle(int n) { System.out.println(“Entering: n = ” + n); if (n == 1) { System.out.println(“Returning 1”); return 1; } else { int temp = n + triangle(n - 1); System.out.println(“Returning“ + temp); return temp; } }? in this example where will the values 2,3,4,5 be stored until the function returns ? note that they will be returned in LIFO(LastInFirstOut) is these a special case of recursion that deals with the memory stack or they always goes together?

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  • Can I make clojure macro that will allow me to get a list of all functions created by the macro?

    - by Rob Lachlan
    I would like to have a macro which I'll call def-foo. Def-foo will create a function, and then will add this function to a set. So I could call (def-foo bar ...) (def-foo baz ...) And then there would be some set, e.g. all-foos, which I could call: all-foos => #{bar, baz} Essentially, I'm just trying to avoid repeating myself. I could of course define the functions in the normal way, (defn bar ...) and then write the set manually. A better alternative, and simpler than the macro idea, would be to do: (def foos #{(defn bar ...) (defn baz ...)} ) But I'm still curious as to whether there is a good way for the macro idea to work.

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  • How can I add methods from a Java class as global functions in Javascript using Rhino?

    - by gooli
    I have a simple Java class that has some methods: public class Utils { public void deal(String price, int amount) { // .... } public void bid(String price, int amount) { // .... } public void offer(String price, int amount) { // .... } } I would like to create an instance of this class and allow the Javascript code to call the methods directly, like so: deal("1.3736", 100000); bid("1.3735", 500000); The only way I could figure out for now was to use ScriptEngine engine = new ScriptEngineManager().getEngineByName("js"); engine.put("utils", new Utils()); and then use utils.deal(...) in the Javascript code. I can also write wrapper functions in Javascript for each method, but there should be a simpler way to do this automatically for all the public methods of a class.

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