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  • Swig typecast to derived class?

    - by Zack
    I notice that Swig provides a whole host of functions to allow for typecasting objects to their parent classes. However, in C++ one can produce a function like the following: A * getAnObject() { if(someBoolean) return (A *) new B; else return (A *) new C; } Where "A" is the parent of classes "B" and "C". One can then typecast the pointer returned into being a "B" type or "C" type at one's convenience like: B * some_var = (B *) getAnObject(); Is there some way I can typecast an object I've received from a generic-pointer-producing function at run-time in the scripting language using the wrappers? (In my case, Lua?) I have a function that could produce one of about a hundred possible classes, and I'd like to avoid writing an enormous switch structure that I'd have to maintain in C++. At the point where I receive the generic pointer, I also have a string representation of the data type I'd like to cast it to. Any thoughts? Thanks! -- EDIT -- I notice that SWIG offers to generate copy constructors for all of my classes. If I had it generate those, could I do something like the following?: var = myModule.getAnObject(); -- Function that returns an object type-cast down to a pointer of the parent class, as in the function getAnObject() above. var = myModule.ClassThatExtendsBaseClass(var); -- A copy constructor that SWIG theoretically creates for me and have var then be an instance of the inheriting class that knows it's an instance of the inheriting class?

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  • How do I define an implicit typecast from my class to a scalar?

    - by Delan Azabani
    I have the following code, which uses a Unicode string class from a library that I'm writing: #include <cstdio> #include "ucpp" main() { ustring a = "test"; ustring b = "ing"; ustring c = "- -"; ustring d; d = "cafe\xcc\x81"; printf("%s\n", (a + b + c[1] + d).encode()); } The encode method of the ustring class instances converts the internal Unicode into a UTF-8 char *. However, because I don't have access to the char class definition, I am unsure on how I can define an implicit typecast (so that I don't have to manually call encode when using with printf, etc).

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  • Typecast to an int in Octave/Matlab

    - by Leif Andersen
    I need to call the index of a matrix made using the linspace command, and based on somde data taken from an oscilloscope. Because of this, the data inputed is a double. However, I can't really call: Time[V0Found] where V0Found is something like 5.2 however, taking index 5 is close enough, so I need to drop the decimal. I used this equation to drop the decimal: V0FoundDec = V0Found - mod(V0Found,1) Time[V0FoundDec] However, eve though that drops the decimal, octave still complains about it. So, what can I do to typecast it to an int? Thank you.

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  • C Typecast: How to

    - by Jean
    #include<stdio.h> int main(void) { unsigned short a,e,f ; // 2 bytes data type unsigned int temp1,temp2,temp4; // 4 bytes data type unsigned long temp3; // 8 bytes data type a=0xFFFF; e=((a*a)+(a*a))/(2*a); // Line 8 //e=(((unsigned long)(a*a)+(unsigned long)(a*a)))/(unsigned int)(2*a); temp1=a*a; temp2=a*a; temp3=(unsigned long)temp1+(unsigned long)temp2; // Line 14 temp4=2*a; f=temp3/temp4; printf("%u,%u,%lu,%u,%u,%u,%u\n",temp1,temp2,temp3,temp4,e,f,a); return(1); } How do I fix the arithmetic (At Line 8 by appropriate typecasting of intermediate results) so that overflows are taken care of ? Currently it prints 65534 instead of expected 65535. Why is the typecast necessary for Line 14 ?

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  • Using Generics to typecast object type to generic type

    - by Shantanu Gupta
    I am very new to generics and trying to implement it. How can i use it here. private T returnValueFromGrid(int RowNo, int ColNo) { return Converter<dgvCurrencyMaster.Rows[RowNo].Cells[ColNo].Value,T>; } I am trying to convert below value to generic type and then return it. dgvCurrencyMaster.Rows[RowNo].Cells[ColNo].Value Here i need to know two things. How to do the above problem and how to use this in my code. Please provide some eg.

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  • Typecast to a type from just the string representation of the type name

    - by Water Cooler v2
    sTypeName = ... //do some string stuff here to get the name of the type /* The Assembly.CreateInstance function returns a type of System.object. I want to type cast it to the type whose name is sTypeName. assembly.CreateInstance(sTypeName) So, in effect I want to do something like: */ assembly.CreateInstance(sTypeName) as Type.GetType(sTypeName); How do I do that? And, what do I take on the left side of the assignment expression, assuming this is C# 2.0. I don't have the var keyword.

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  • C++ adding friend to a template class in order to typecast

    - by user1835359
    I'm currently reading "Effective C++" and there is a chapter that contains code similiar to this: template <typename T> class Num { public: Num(int n) { ... } }; template <typename T> Num<T> operator*(const Num<T>& lhs, const Num<T>& rhs) { ... } Num<int> n = 5 * Num<int>(10); The book says that this won't work (and indeed it doesn't) because you can't expect the compiler to use implicit typecasting to specialize a template. As a soluting it is suggested to use the "friend" syntax to define the function inside the class. //It works template <typename T> class Num { public: Num(int n) { ... } friend Num operator*(const Num& lhs, const Num& rhs) { ... } }; Num<int> n = 5 * Num<int>(10); And the book suggests to use this friend-declaration thing whenever I need implicit conversion to a template class type. And it all seems to make sense. But why can't I get the same example working with a common function, not an operator? template <typename T> class Num { public: Num(int n) { ... } friend void doFoo(const Num& lhs) { ... } }; doFoo(5); This time the compiler complaints that he can't find any 'doFoo' at all. And if i declare the doFoo outside the class, i get the reasonable mismatched types error. Seems like the "friend ..." part is just being ignored. So is there a problem with my understanding? What is the difference between a function and an operator in this case?

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  • Typecast cross-platform compatibility

    - by kaykun
    Hi, what I'm trying to do is append a binary integer into a string object. So far I have this: int number = 5; cppstring.append((char*)&number, 4); It works fine on a x86 system with Windows, but some people are saying its not cross-platform and is unsafe. What is the preferred method to do this?

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  • How do i cast an object to a string when object is not a string?

    - by acidzombie24
    I have class A, B, C. They all can implicitly convert to a string public static implicit operator A(string sz_) { ... return sz; } I have code that does this object AClassWhichImplicitlyConvertsToString { ... ((KnownType)(String)AClassWhichImplicitlyConvertsToString).KnownFunc() } The problem is, AClassWhichImplicitlyConvertsToString isnt a string even though it can be typecast into one implicitly. I get a bad cast exception. How do i say its ok as long as the class has an operator to convert into a string?

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  • Typecasting a floating value or using the math.h floor* functions?

    - by nobody
    Hi, I am coding up an implementation of Interpolation Search in C. The question is actually rather simple, I need to use the floating operations to do linear interpolation to find the correct index which will eventually be an integer result. In particular my probe index is: t = i + floor((((k-low)/(high-low)) * (j-i))); where, i,j,k,t are unsigned ints, and high,low are doubles. Would this be equivalent to: t = i + (unsigned int)(((k-low)/(high-low)) * (j-i)); Is there any reason I would actually want to use math.h floor* functions over just a simple (int) typecast?

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  • What makes the availability of both primitive and object-wrapped values in JavaScript useful?

    - by Delan Azabani
    I wrote a blog post a while ago detailing how the availability of both primitive and object-wrapped value types in JavaScript (for things such as Number, String and Boolean) causes trouble, including but not limited to type-casting to a boolean (e.g. object-wrapped NaN, "" and false actually type-cast to true). My question is, with all this confusion and problems, is there any benefit to JavaScript having both types of values for the built-in classes?

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  • cast operator to base class within a thin wrapper derived class

    - by miked
    I have a derived class that's a very thin wrapper around a base class. Basically, I have a class that has two ways that it can be compared depending on how you interpret it so I created a new class that derives from the base class and only has new constructors (that just delegate to the base class) and a new operator==. What I'd like to do is overload the operator Base&() in the Derived class so in cases where I need to interpret it as the Base. For example: class Base { Base(stuff); Base(const Base& that); bool operator==(Base& rhs); //typical equality test }; class Derived : public Base { Derived(stuff) : Base(stuff) {}; Derived(const Base& that) : Base(that) {}; Derived(const Derived& that) : Base(that) {}; bool operator==(Derived& rhs); //special case equality test operator Base&() { return (Base&)*this; //Is this OK? It seems wrong to me. } }; If you want a simple example of what I'm trying to do, pretend I had a String class and String==String is the typical character by character comparison. But I created a new class CaseInsensitiveString that did a case insensitive compare on CaseInsensitiveString==CaseInsensitiveString but in all other cases just behaved like a String. it doesn't even have any new data members, just an overloaded operator==. (Please, don't tell me to use std::string, this is just an example!) Am I going about this right? Something seems fishy, but I can't put my finger on it.

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  • how to get output of a variable as float value

    - by jaskirat
    hi..i m having the follwing problem.. want to get the result in float suppose int a= convert.toint32(textbox1.text); int b= convert.toint32(textbox2.text); float ans= math.sqrt(a*b); label1.text= ans.tostring(); output.. a=7 b=3 ans should be= 4.582 but i get an error cannot implicitly convert type 'double' to 'float'. pls help..how can i get the float ans...

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  • Window Wrapper Class C++ (G++)

    - by Ell
    Hi all, I am attempting to learn about creating windows in c++, I have looked at an article about creating a wrapper class but I don't really understand it. So far I know that you can't have a class method WndProc (I dont know why) but honestly, that is all. Can somebody give an explanation, also explaining the reinterpret_cast? Here is the article. LRESULT CALLBACK Window::MsgRouter(HWND hwnd, UINT message, WPARAM wparam, LPARAM lparam) { Window *wnd = 0; if(message == WM_NCCREATE) { // retrieve Window instance from window creation data and associate wnd = reinterpret_cast<Window *>((LPCREATESTRUCT)lparam)->lpCreateParams; ::SetWindowLong(hwnd, GWL_USERDATA, reinterpret_cast<long>(wnd)); // save window handle wnd->SetHWND(hwnd); } else // retrieve associated Window instance wnd = reinterpret_cast<Window *>(::GetWindowLong(hwnd, GWL_USERDATA)); // call the windows message handler wnd->WndProc(message, wparam, lparam); } Thanks in advance, ell.

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  • Should I typecast in PHP when defining my vars?

    - by Borislav
    I am sorry if this is more of a theory question then a real life problem but it is a real life situation for me. We were commenting on the way PHP works with vars and how memory heavy it is on the server due to its "mixed vars" and something occured to me - why not typecast right from the start? So I guess my quesion is: Whould it make any difference for the server load if all you PHP vars were"pre-casted"? Example: protected $_id; VS protected (int) $_id;

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  • Is there an easier way to typecast with unknown types?

    - by Adam S
    Hi all. I am writing a function to recurse my XAML and add all the controls to a hashtable, with their names being the keys. Unfortunately it seems like I have to go through and list every possible type: void Recurse_Controls(object start) { string start_type = start.GetType().ToString(); if (start_type == "StackPanel") { ControlsByName.Add(((StackPanel)start).Name, start); foreach (object item in ((StackPanel)start).Children) { Recurse_Controls(item); } } if (start_type == "Grid") { ControlsByName.Add(((Grid)start).Name, start); foreach (object item in ((Grid)start).Children) { Recurse_Controls(item); } } } Is there a simpler way of doing this?

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  • java classcast exception

    - by shil
    hi i have problems in converting an XML document type into a Document object.. this is the piece of code line 1 : Document doc=null; line 2 : doc = (Document) parser.parse(sourceFile); for this line 2 it throws java classcast exception.. without the typecast it shows error as "Type mismatch: cannot convert from org.w3c.dom.Document to javax.swing.text.Document" how do i now typecast properly? any suggestions??

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  • Events Driven Library XNA C#

    - by SchautDollar
    Language: C# w/ XNA Framework Relevant and Hopefully Helpful Background Info: I am making a library using the XNA framework for games I make with XNA. The Library has a folder(Namespace) dedication to the GUI. The GUI Controls inherit a base class hooked with the appropriate Interfaces. After a control is made, the programmer can hook the control with a "Frame" or "Module" that will tell the controls when to update and draw with an event. To make a "Frame" or "Module", you would inherit a class with the details coded in. (Kind of how win forms does it.) My reason for doing this is to simplify the process of creating menus with intractable controls. The only way I could think of for making the events for all the controls to function without being class specific would be to typecast a control to an object and typecast it back. (As I have read, this can be terribly inefficient.) Problem: Unfortunately, after I have implemented interfaces into the base classes and changed public delegate void ClickedHandler(BaseControl cntrl); to public delegate void ClickedHandler(Object cntrl, EventArgs e); my game has decreased in performance. This performance could be how I am firing the events, as what happens is the one menu will start fine, but then slowly but surely will freeze up. Every other frame works just fine, I just think it has something to do with the events and... that is why I am asking about them. Question: Is there a better more industry way of dealing with GUI Libraries other then using and implementing Events? Goal: To create a reusable feature rich XNA Control Library implementing performance enhancing standards and so on. Thank-you very much for taking your time to read this. I also hope this will help others possibly facing what I am facing right now.

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  • How to expose service contract interfaces with multiple inheritance in WCF service on single endpoin

    - by Vaibhav Gawali
    I have only simple data types in method signature of service (such as int, string). My service class implements single ServiceContract interface say IMathService, and this interface in turn inherits from some other base interface say IAdderService. I want to expose the MathService using interface contract IAdderService as a service on a single endpoint. However some of the clinet's which know about IMathService should be able to access the extra services provided by IMathService on that single endpoint i.e. by just typecasting IAdderService to IMathService. //Interfaces and classes at server side [ServiceContract] public interface IAdderService { [OperationContract] int Add(int num1, int num2); } [ServiceContract] public interface IMathService : IAdderService { [OperationContract] int Substract(int num1, int num2); } public class MathService : IMathService { #region IMathService Members public int Substract(int num1, int num2) { return num1 - num2; } #endregion #region IAdderService Members public int Add(int num1, int num2) { return num1 + num2; } #endregion } //Run WCF service as a singleton instace MathService mathService = new MathService(); ServiceHost host = new ServiceHost(mathService); host.Open(); Server side Configuration: <configuration> <system.serviceModel> <services> <service name="IAdderService" behaviorConfiguration="AdderServiceServiceBehavior"> <endpoint address="net.pipe://localhost/AdderService" binding="netNamedPipeBinding" bindingConfiguration="Binding1" contract="TestApp.IAdderService" /> <endpoint address="mex" binding="mexNamedPipeBinding" contract="IMetadataExchange" /> <host> <baseAddresses> <add baseAddress="net.pipe://localhost/AdderService"/> </baseAddresses> </host> </service> </services> <bindings> <netNamedPipeBinding> <binding name="Binding1" > <security mode = "None"> </security> </binding > </netNamedPipeBinding> </bindings> <behaviors> <serviceBehaviors> <behavior name="AdderServiceServiceBehavior"> <serviceMetadata /> <serviceDebug includeExceptionDetailInFaults="True" /> </behavior> </serviceBehaviors> </behaviors> </system.serviceModel> </configuration> Client Side imeplementation: IAdderService adderService = new ChannelFactory<IAdderService>("AdderService").CreateChannel(); int result = adderService.Add(10, 11); IMathService mathService = adderService as IMathService; result = mathService.Substract(100, 9); Client side configuration: <configuration> <system.serviceModel> <client> <endpoint name="AdderService" address="net.pipe://localhost/AdderService" binding="netNamedPipeBinding" bindingConfiguration="Binding1" contract="TestApp.IAdderService" /> </client> <bindings> <netNamedPipeBinding> <binding name="Binding1" maxBufferSize="65536" maxConnections="10"> <security mode = "None"> </security> </binding > </netNamedPipeBinding> </bindings> </system.serviceModel> </configuration> Using above code and configuration I am not able to typecast IAdderService instnace to IMathService, it fails and I get null instance of IMathService at client side. My observation is if server exposes IMathService to client then client can safely typecast to IAdderService and vice versa is also possible. However if server exposes IAdderService then the typecast fails. Is there any solution to this? or am I doing it in a wrong way.

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