casting

boost::dynamic_pointer_cast with const pointer not working ?

Hi, Let's say I have two classes, A and B, where B is a child class of A. I also have the following function: void foo(boost::shared_ptr<const A> a) { boost::shared_ptr<const B> b = boost::dynamic_pointer_cast<const B>(a); // Error ! } Compilation with gcc gives me the following errors: C:\Boost\include/boost/smart_ptr/shared_p...

Could this C cast to avoid a signed/unsigned comparison make any sense?

I'm reviewing a C++ project and see effectively the following: std::vector<SomeType> objects; //then later int size = (int)objects.size(); for( int i = 0; i < size; ++i ) { process( objects[i] ); } Here's what I see. std::vector::size() returns size_t that can be of some size not related to the size of int. Even if sizeof(int) ==...

What is CDbl doing?

I had until recently been under the impression that the CDbl(x) operation in VB.NET was essentially a cast (i.e., the VB equivalent of (double)x in C#); but a recent discovery has revealed that this is not the case. If I have this string: Dim s As String = "12345.12345-" And I do this: Dim d As Double = CDbl(s) d will be set to th...

C2664 when casting child class to templated parent class

I have a parent class which is templated, and a child class which implements it. template< typename T1, typename T2> class ParentClass{ . . . }; class ChildClass : public ParentClass<MyT1, MyT2> { . . . }; And I want to have a pointer which I can use polymorphically: ParentClass<T1, T2>* ptr; ptr = static_cast<ParentClass<MyT1, MyT2>...

Java - How to avoid loss of precision during divide and cast to int?

I have a situation where I need to find out how many times an int goes into a decimal, but in certain cases, I'm losing precision. Here is the method: public int test(double decimalAmount, int divisor) { return (int) (decimalAmount/ (1d / divisor)); } The problem with this is if I pass in 1.2 as the decimal amount and 5 as the divi...

Cast MyEntity To LinqEntity throw a base controller class

hi there i design a multilayer we appliction andusing LINQ a my data provider i need to user my own Entites instead o LINQ etities. so i created Entities Project and create my entities in it. when i get data from contex and cast them to my entities , everything is ok. but when i want to cast on of my entities to linq entity , an excepti...

Casting in mixed type calculations in C?

Hi, If I define these variables: double x0, xn, h; int n; and I have this mathematical expression: h = (xn - x0)/n; Is it necessary that I cast n into double prior doing the division for maximum accuracy like in h = (xn - x0)/ (double) n; I wrote a program to check the above but both expressions give the same answers. I understa...

templates and casting operators

This code compiles in CodeGear 2009 and Visual Studio 2010 but not gcc. Why? class Foo { public: operator int() const; template <typename T> T get() const { return this->operator T(); } }; Foo::operator int() const { return 5; } The error message is: test.cpp: In member function `T Foo::get() const': test.cpp:6: error:...

Casting generics and the generic type

Consider, I have the following 3 classes / interfaces: class MyClass<T> { } interface IMyInterface { } class Derived : IMyInterface { } And I want to be able to cast a MyClass<Derived> into a MyClass<IMyInterface> or visa-versa: MyClass<Derived> a = new MyClass<Derived>(); MyClass<IMyInterface> b = (MyClass<IMyInterface>)a; But I...

Casting and dynamic vs static type in Java

I'm learning about static vs dynamic types, and I am to the point of understanding it for the most part, but this case still eludes me. If class B extends A, and I have: A x = new B(); Is the following allowed?: B y = x; Or is explicit casting required?: B y = (B)x; Thanks! ...

Trouble converting a stored unix time() stamp into a readable date time

So, $logarray[$row]["time"] is fetched from a MySQL table and placed into an array. The value is stored as a 10 digit int. When I try to pass it into the second parameter of date(), it tells me its expecting a long type, not a string type. So, I tried casting it into an int (couldn't find a long caster...). The error went away, but now i...

Invalid conversion from int to int** C++

Not sure why I'm getting this error. I have the following: int* arr = new int[25]; int* foo(){ int* i; cout << "Enter an integer:"; cin >> *i; return i; } void test(int** myInt){ *myInt = foo(); } This call here is where I get the error: test(arr[0]); //here i get invalid conversion from int to int** ...

Casting Generic Types

Public Function CastToT(Of T)(ByVal GenericType(Of Object) data) As GenericType(Of T) Return DirectCast(data, GenericType(Of T)) End Function The above clearly does not work. Is there any way to perform this cast if I know that all objects inside data are in fact of Type T? ...

Need to cast to an object without knowing what type the object is

I am trying to dynamically load my authentication server type based on a setting. I am hung up on how to cast to a type when I don't know the type. Type t = Type.GetType(WebConfigurationManager.AppSettings.Get("AuthenticationSvcImpl")); IAuthenticationService authCli = Activator.CreateInstance(t); return authCli.Authenticat...

Casting DataTypes with DirectCast, CType, TryCast

Ever since I moved from VB6 to VB.NET somewhere in 2005, I've been using CType to do casting from one data type to another. I do this because it is simply faster to type, used to exist in VB6 and I do not know why I have to be using DirectCast if there is apparently no difference between them. I use TryCast once in a while because I und...

C++ delete static_cast<void*>(pointer) behavior

suppose the code does the following: T *pointer = new T(); delete static_cast<void*>(pointer); what is result? Undefined, memory leak, memory is deleted? Thanks ...

Java - short and casting

Hi all, I have the following code snippet. public static void main(String[] args) { short a = 4; short b = 5; short c = 5 + 4; short d = a; short e = a + b; // does not compile (expression treated as int) short z = 32767; short z_ = 32768; // does not compile (out of range) test(a); test(7); // does not compile (not applica...

Invalid cast exception

I have a simple application to store address details and edit them. I have been away from VB for a few years now and need to refreash my knowledge while working to a tight deadline. I have a general Sub responsible for displaying a form where user can add contact details (by pressing button add) and edit them (by pressing button edit)....

Casting Between Data Types in C#

I have (for example) an object of type A that I want to be able to cast to type B (similar to how you can cast an int to a float) Data types A and B are my own. Is it possible to define the rules by which this casting occurs? Example int a = 1; float b = (float)a; int c = (int)b; ...

Which is preferred: new Nullable<int> or (int?)null ?

Which way is preferred in expressions like this: int? Id { get { int i; return Int32.TryParse(Request["id"], out i) ? i : (int?)null; } } is it better to cast on null or create a new Nullable<T> ? ...