I am trying to change the value of a variable which is defined as int const as below. const int w = 10; int* wp = const_cast <int*> (&w); *wp = 20; The value of w didn't change and was 10 even after the assignment, though it shows as if both w and wp are pointing to the same memory location. But I am able to the change the value of w,...
Please help me understand the following signature: err_type funcName(const Type& buffer) const; so for the first const, does that mean the contents of Type cannot change or that the reference cannot change? secondly, what does the second const mean? I don't really even have a hint. Thanks in advance, jbu ...
Greetings, I'm a beginner to OO and programming and I have the following situation: I have a set of const values and enums that several of the classes I implement share. These classes are independent i.e. other than sharing these values, they do not interact with each other, so inheriting them won't work. I was wondering; If I create...
in int salary() const { return mySalary; } as far as I understand const is for this pointer, but I'm not sure. Can any one tell me what is the use of const over here? Thanks ...
Hi! is it possible/ok to return a const reference even if the value the function returns is a local variable of this function? i know that locals are not valid anymore once the function returns - but what if the function is inlined and the returned value is only used within the callers scope? then the locals of the function should be in...
I'm a const fiend, and I strive to make everything as const as possible. I've tried looking at various dissassembly outputs from const and non const versions of functions, and I've yet to see a marked improvement however. I'm assuming compilers nowadays are able to do smart things with non const functions that could technically be cons...
I have a few containers in a class, for example, vector or map which contain shared_ptr's to objects living on the heap. For example template <typename T> class MyExample { public: private: vector<tr1::shared_ptr<T> > vec; map<tr1::shared_ptr<T> , int> h; }; I want to have a public interface of this class that sometimes returns sh...
Hi all, I am having trouble deciphering a "passing argument ... from distinct Objective-C type warning". I have a constant string declared as: extern NSString * const URL_1; and defined as: NSString * const URL_1 = @"http://someurl"; If I, say, assign that constant to an NSString as follows: NSString *URL = nil; ... URL = [[NSSt...
What is the significance of the positioning of the const keyword when declaring a variable in Objective-C, for example: extern const NSString * MY_CONSTANT; versus extern NSString * const MY_CONSTANT; Using the first version in assignments produces warnings about "qualifiers from pointer target type" being discarded so I'm assum...
I am using Visual C++ 2008's GUI creator to make a user interface. When a button is clicked, the following function is called. The content is supposed to create a file and name the file after the contents of the textbox "Textbox' with '.txt' at the end. However, that leads me to a conversion error. Here is the code: private: System::Vo...
Hello Consider this void f(vector<const T*>& p) { } int main() { vector<T*> nonConstVec; f(nonConstVec); } The following does not compile.The thing is that vector<T*> can not be converted to vector <const T*> , and that seems illogically to me , because there exists implicit conversion from T* to const T*. Why is this ? v...
I need to loop a const char, and I've used a simple example of string loop: const char *str; for(int i = 0; i < 10; ++i) { str += " "; } But when I tried to compile, I got this: ubuntu@eeepc:~/Test_C_OS$ gcc -o kernel.o -c kernel.c -Wall -Wextra -nostdlib -nostartfiles -nodefaultlibs kernel.c:26: error: ‘for’ loop initial dec...
I seem to have this pattern occuring pretty often in my code, with two functions performing the same task apart from the constness of their parameters/returns. int& myClass::getData() { return data; } // called for const objects const int& myData::getData() const { return data; } This offends my sense of DRY. It's no...
Hey all. I was hoping that if I were to define constants in a separate namespace, like: <?php namespace config\database\mysql; const HOST = 'localhost'; const USER = 'testusr'; const PASSWORD = 'testpwd'; const NAME = 'testdb'; ?> That I would be able to use __autoload to automatically include them: <?php function __autoload($clas...
I know how to publish a const of a simple type in IDL, for example: const long blah = 37 But I want to publish consts of complex types, with methods, or at least readable struct-like member fields. For example, perhaps a type called CarType, which has accessor fields like "get_Make", "get_Model", "get_Year", "get_BasePrice", et ceter...
I am trying to figure out how I want to handle settings in my PHP app. I have pretty much decide that I would like to use a Confg class file so it will be autoloaded and flexible in the future. Below is some stuff I was playing with. I know you cannot set a variable to popluate a Constant so I then try to use a public static propert...
Anybody knows the technical reason why this constraint is placed on PHP classes (at least in v5.1x)? ...
Suppose i have declared subscript operators in a class char& operator[] (int index); const char operator[](int index) const; In what condition the second overload is called. Is it only called through a const object. In the following scenarios which version of operator will be called. const char res1 = nonConstObject[10]; nonCons...
I've heard and read many times that's better to catch an exception as reference-to-const rather than as reference. Why is try { // stuff } catch (const std::exception& e) { // stuff } better than try { // stuff } catch (std::exception& e) { // stuff } ...
Edit1: I realize this is hard to understand this question without having an insight of what I'm trying to do. The class A is not complete but it essentially stand for a C-array "proxy" (or "viewer" or "sampler"). One interesting usage is too present a C-array as a 2d grid (the relevant function are not shown here). The property of this c...