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  • A simple question about type coercion in C++

    - by David
    Given a function prototype, and a type definition: int my_function(unsigned short x); typedef unsigned short blatherskite; Is the following situation defined by standard: int main(int argc, char** argv) { int result; blatherskite b; b=3; result = my_function(b); } Do I get type coercion predictably via the function prototype?

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  • MySql TABLE data type

    - by Neil Aitken
    MS SQL Server has a TABLE data type which can be used in stored procedures, Does anybody know if MySQL has an equivalent data type? I've had a look over the docs but can't seem to find anything, so I presume it doesn't exist, but perhaps somebody has created a workaround

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  • java mapping for oracle number type

    - by aauser
    I have database with oracle number type. Could there any possible issues with using java Double when updating table with numeric column. Should i switch BigDecimal or Double is approriate type. As I fas as I know, BigDecimal is used when arbitrary precision required, when deal with prices for example. Consider simple API updatePrice(Double d) Should i persist double as is or BigDecimal.valueOf(d) is preferable ?

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  • C# Type Casting at Runtimefor Array.SetValue

    - by sprocketonline
    I'm trying to create an array using reflection, and insert values into it. I'm trying to do this for many different types so would like a createAndFillArray function capable of this : Type t1 = typeof(A); Type t2 = typeof(B); double exampleA = 22.5; int exampleB = 43; Array arrA = createAndFillArray(t1, exampleA); Array arrB = createAndFillArray(t2, exampleB); private Array createAndFillArray(Type t, object val){ Array arr = Array.CreateInstance( t, 1); //length 1 in this example only, real-world is of variable length. arr.SetValue( val, 0 ); //this causes the following error: "System.InvalidCastException : Object cannot be stored in an array of this type." return arr; } with the class A being as follows: public class A{ public A(){} private double val; public double Value{ get{ return val; } set{ this.val = value; } } public static implicit operator A(double d){ A a = new A(); a.Value = d; return a; } } and class B being very similar, but with int: public class B{ public B(){} private double val; public double Value{ get{ return val; } set{ this.val = value; } } public static implicit operator B(double d){ B b = new B(); b.Value = d; return b; } } I hoped that the implicit operator would have ensured that the double be converted to class A, or the int to class B, and the error avoided; but this is obviously not so. The above is used in a custom deserialization class, which takes data from a custom data format and fills in the corresponding .Net object properties. I'm doing this via reflection and at runtime, so I think both are unavoidable. I'm targeting the C# 2.0 framework. I've dozens, if not hundreds, of classes similar to A and B, so would prefer to find a solution which improved on the createAndFillArray method rather than a solution which altered these classes.

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  • C++: get const or non-const reference type from trait

    - by maciekp
    I am writing a functor F which takes function of type void (*func)(T) and func's argument arg. Then functor F calls func with arg. I would like F not to copy arg, just to pass it as reference. But then I cannot simply write "void F(void (*func)(T), T&)" because T could be a reference. So I am trying to write a trait, which allows to get proper reference type of T: T -> T& T& -> T& const T -> const T& const T& -> const T& I come up with something like this: template<typename T> struct type_op { typedef T& valid_ref_type; }; template<typename T> struct type_op<T&> { typedef typename type_op<T>::valid_ref_type valid_ref_type; }; template<typename T> struct type_op<const T> { typedef const T& valid_ref_type; }; template<typename T> struct type_op<const T&> { typedef const T& valid_ref_type; }; Which doesn't work for example for void a(int x) { std::cout << x << std::endl; } F(&a, 7); Giving error: invalid initialization of non-const reference of type ‘int&’ from a temporary of type ‘int’ in passing argument 2 of ‘void f(void (*)(T), typename type_op::valid_ref_type) [with T = int]’ How to get this trait to work?

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  • Interop type cannot be embedded

    - by Jan
    I am creating an web application on the .net 4.0 framework (beta2 ) in C#. When I try to use a assembly called "ActiveHomeScriptLib", I get the following error: Interop type 'ActiveHomeScriptLib.ActiveHomeClass' cannot be embedded. Use the applicable interface instead. When I change the framework to version 3.5, I don't have any errors. What is an Interop Type and why does this only occur when I use the 4.0 framework.

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  • How to convert a PGresult to custom data type with libpq (PostgreSQL)

    - by mocopera
    Hi everyone! I'm using the libpq library in C to accessing my PostgreSQL database. So, when I do res = PQexec(conn, "SELECT point FROM test_point3d"); I don't know how to convert the PGresult I got to my custom data type. I know I can use the PQgetValue function, but again I don't know how to convert the returning string to my custom data type. Any suggestion? Thanks in advice.

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  • Nullable type conversion in C#?

    - by dinesh
    Hi can we assign null value to struct type of variable? struct MyStruct { } MyStruct var = null; is this is possible in C# .net? if not ? then how C# is allowing Nullable < T struct type of variable can be assigned as null?

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  • F# compilation error: Unexpected type application

    - by Jim Burger
    In F#, given the following class: type Foo() = member this.Bar<'t> (arg0:string) = ignore() Why does the following compile: let f = new Foo() f.Bar<Int32> "string" While the following won't compile: let f = new Foo() "string" |> f.Bar<Int32> //The compiler returns the error: "Unexpected type application"

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  • Get drive type with SetupDiGetDeviceRegistryProperty

    - by new
    Dear all, I would like to know whether i can get the drive information using the SP_DEVICE_INTERFACE_DETAIL_DATA's DevicePath my device path looks like below "\?\usb#vid_04f2&pid_0111#5&39fe81e&0&2#{a5dcbf10-6530-11d2-901f-00c04fb951ed}" also please tell me in the winapi they say "To determine whether a drive is a USB-type drive, call SetupDiGetDeviceRegistryProperty and specify the SPDRP_REMOVAL_POLICY property." i too use SetupDiGetDeviceRegistryProperty like below while ( !SetupDiGetDeviceRegistryProperty( hDevInfo,&DeviceInfoData, SPDRP_REMOVAL_POLICY,&DataT,( PBYTE )buffer,buffersize,&buffersize )) but i dont know how can i get the drive type using the above.. Please help me up

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  • Hook perm for more than one content type

    - by Andrew
    Drupal 6.x I have this module that manages four different content types. For that matter, how do I define permission for each content within the same module? Is that even possible? I can't figure out how to define permission for each content type cuz hook_perm has to be named with module name and it doesn't have any argument(like hook_access $node) to return permission base on content type. Any help would be highly appreciated.

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  • converting an interface to a type in MVC

    - by danielovich
    Hi. I have a small isuse regarding an interface. Consider this code: [HttpPost()] public void Update(IAuctionItem item) { RedirectToAction("List"); } Whenever I call this I get an exception saying I can't create an instance of type which i totally correct. But is there a way of telling what the interface should map to without actually using the concrete type ?

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  • Reflection problem - Type Safety Warning

    - by jax
    Class<? extends Algorithm> alg = AlgorithmAllFrom9AndLastFrom10Impl.class Constructor<Algorithm> c = alg.getConstructors()[0]; For "alg.getConstructors()[0];" I am getting a warning in eclipse Type safety: The expression of type Constructor needs unchecked conversion to conform to Constructor How do I fix this?

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  • Get derived class type from a base's class static method

    - by Marco Bettiolo
    Hi, i would like to get the type of the derived class from a static method of its base class. How can this be accomplished? Thanks! class BaseClass { static void Ping () { Type t = this.GetType(); // should be DerivedClass, but it is not possible with a static method } } class DerivedClass : BaseClass {} // somewhere in the code DerivedClass.Ping();

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  • C++ dynamic type construction and detection

    - by KneLL
    There was an interesting problem in C++, but it concerns more likely architecture. There are many (10, 20, 40, etc) classes that describe some characteristics (mix-in classes), for exmaple: struct Base { virtual ~Base() {} }; struct A : virtual public Base { int size; }; struct B : virtual public Base { float x, y; }; struct C : virtual public Base { bool some_bool_state; }; struct D : virtual public Base { string str; } // .... Primary module declares and exports a function (for simplicity just function declarations without classes): // .h file void operate(Base *pBase); // .cpp file void operate(Base *pBase) { // .... } Any other module can has a code like this: #include "mixins.h" #include "primary.h" class obj1_t : public A, public C, public D {}; class obj2_t : public B, public D {}; // ... void Pass() { obj1_t obj1; obj2_t obj2; operate(&obj1); operate(&obj2); } The question is how to know what the real type of given object in operate() without dynamic_cast and any type information in classes (constants, etc)? Function operate() is used with big array of objects in small time periods and dynamic_cast is too slow for it. And I don't want to include constants (enum obj_type { ... }) because this is not OOP-way. // module operate.cpp void some_operate(Base *pBase) { processA(pBase); processB(pBase); } void processA(A *pA) { } void processB(B *pB) { } I cannot directly pass a pBase to these functions. And it's impossible to have all possible combinations of classes, because I can add new classes just by including new .h files. As one of solutions that comed to mind, in editor application I can use a composite container: struct CompositeObject { vector<Base *pBase> parts; }; But editor does not need a time optimization and can use dynamic_cast for parts to determine the exact type. In operate() I cannot use this solution. So, is it possible to not use a dynamic_cast and type information to solve this problem? Or maybe I should use another architecture?

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  • Parsing values from XML into types of Type

    - by DrLazer
    check this out Type configPropType = configurableProp.getPropertyType(); string attValue = xmlelement.GetAttribute(configurableProp.getName()); configProps[configurableProp.getName()] = attValue; At the point where I am setting the value that got read in from XML it turns out the assigning object needs to be parsed to the correct type for it to work. I need something like. configProps[configurableProp.getName()] = configPropType.ParseToThisType(attValue); Looked around on msdn but its a very confusing place.

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  • SQL Server Text type v.s. varchar data type

    - by George2
    Hello everyone, I have variable length character and want to store in SQL Server (2005) database. I want to learn some best practices about how to choose TEXT SQL type or choose VARCHAR SQL type, pros and cons in performance/footprint/function. thanks in advance, George

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