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  • Casting Class into String and Vice Versa in JAVA

    - by topgun_ivard
    I have a program in which I need to store a Class object into memory by casting it into String. Is it possible to convert the String back into the original Class so that I can use that class variables? I am doing this in JAVA. Example: test.java class hello{ public String h1; public String h2; } public class test { public static void main(String[] args) { hello h = new hello(); h.h1 = "hello"; h.h2 = "world"; String s = h.toString(); System.out.println("Print s : "+s); // Now I need to convert String s into type hello so that // I can do this: // (hello)s.h1; // (hello)s.h2; } } NOTE: this is not a homework, this is a personal project and I would be grateful if anyone can help! Thanks! Ivar

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  • possible implementations of casting in c++

    - by lego69
    I have this snippet of the code in my header: class A { private: int player; public: A(int initPlayer = 0); A(const A&); A& operator=(const A&); ~A(); void foo() const; friend int operator==(const A& i, const A& member) const; }; implementation of the operator== int operator==(const A& i, const A& member) const{ if(i.player == member.player){ return 1; } return 0; } and I need casting for this part of my code: A *pa1 = new A(a2); assert(i == *pa1); i - is some int, which my function receives I receive an error non-member function, How can I fix it? thanks in advance

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  • In asp classic: How can I make sure that a variable can be cast as an int?

    - by Tchalvak
    The following function was suggested to me: ' Defines a forced casting function, which "casts" anything that it can't detect as a number to zero. Function MakeInteger(val) If IsNumeric(val) Then MakeInteger = CInt(val) Else MakeInteger = 0 End If End Function Unfortunately there appear to be some things that return true for IsNumeric() but still can't be cast as an int. Is there any better check to use?

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  • Why does this compile?

    - by akf
    I was taken aback earlier today when debugging some code to find that something like the following does not throw a compile-time exception: public Test () { HashMap map = (HashMap) getList(); } private List getList(){ return new ArrayList(); } As you can imagine, a ClassCastException is thrown at runtime, but can someone explain why the casting of a List to a HashMap is considered legal at compile time?

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  • GCC doesn't like C++ style casts with spaces

    - by uj2
    I am porting some C++ code to GCC, and apperantly it isn't happy with C++ style casting when sapces are involved, as in unsigned int(-1), long long(ShortVar) etc... It gives an error: expected primary-expression before 'long'. Is there any way to make peace with GCC without going over each one of those and rewrite in c-style?

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  • Storing a type in C++

    - by perimosocordiae
    Is it possible to store a type name as a C++ variable? For example, like this: type my_type = int; // or string, or Foo, or any other type void* data = ...; my_type* a = (my_type*) data; I know that 99.9% of the time there's a better way to do what you want without resorting to casting void pointers, but I'm curious if C++ allows this sort of thing.

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  • Does (size_t)((char *)0) ever not evaluate to 0?

    - by Bruce Christensen
    According to the responses in "Why subtract null pointer in offsetof()?" (and my reading of K&R), the C standard doesn't require that (size_t)((char *)0) == 0. Still, I've never seen a situation where casting a null pointer to an integer type evaluates to anything else. If there is a compiler or scenario where (size_t)((char *)0) != 0, what is it?

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  • What is a technique for 2D ray-box intersection that is suitable for old console hardware?

    - by DJCouchyCouch
    I'm working on a Sega Genesis homebrew game (it has a 7mhz 68000 CPU). I'm looking for a way to find the intersection between a particle sprite and a background tile. Particles are represented as a point with a movement vector. Background tiles are 8 x 8 pixels, with an (X,Y) position that is always located at a multiple of 8. So, really, I need to find the intersection point for a ray-box collision; I need to find out where along the edge of the tile the ray/particle hits. I have these two hard constraints: I'm working with pixel locations (integers). Floating point is too expensive. It doesn't have to be super exact, just close enough. Multiplications, divisions, dot products, et cetera, are incredibly expensive and are to be avoided. So I'm looking for an efficient algorithm that would fit those constraints. Any ideas? I'm writing it in C, so that would work, but assembly should be good as well.

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  • C# 4.0: casting dynamic to static

    - by Kevin Won
    This is an offshoot question that's related to another I asked here. I'm splitting it off because it's really a sub-question: I'm having difficulties casting an object of type dynamic to another (known) static type. I have an ironPython script that is doing this: import clr clr.AddReference("System") from System import * def GetBclUri(): return Uri("http://google.com") note that it's simply newing up a BCL System.Uri type and returning it. So I know the static type of the returned object. now over in C# land, I'm newing up the script hosting stuff and calling this getter to return the Uri object: dynamic uri = scriptEngine.GetBclUri(); System.Uri u = uri as System.Uri; // casts the dynamic to static fine Works no problem. I now can use the strongly typed Uri object as if it was originally instantiated statically. however.... Now I want to define my own C# class that will be newed up in dynamic-land just like I did with the Uri. My simple C# class: namespace Entity { public class TestPy // stupid simple test class of my own { public string DoSomething(string something) { return something; } } } Now in Python, new up an object of this type and return it: sys.path.append(r'C:..path here...') clr.AddReferenceToFile("entity.dll") import Entity.TestPy def GetTest(): return Entity.TestPy(); // the C# class then in C# call the getter: dynamic test = scriptEngine.GetTest(); Entity.TestPy t = test as Entity.TestPy; // t==null!!! here, the cast does not work. Note that the 'test' object (dynamic) is valid--I can call the DoSomething()--it just won't cast to the known static type string s = test.DoSomething("asdf"); // dynamic object works fine so I'm perplexed. the BCL type System.Uri will cast from a dynamic type to the correct static one, but my own type won't. There's obviously something I'm not getting about this...

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  • Casting to a struct from LPVOID - C

    - by Jamie Keeling
    Hello, I am writing a simple console application which will allow me to create a number of threads from a set of parameters passed through the arguments I provide. DWORD WINAPI ThreadFunc(LPVOID threadData) { } I am packing them into a struct and passing them as a parameter into the CreateThread method and trying to unpack them by casting them to the same type as my struct from the LPVOID. I'm not sure how to cast it to the struct after getting it through so I can use it in the method itself, i've tried various combinations (Example attatched) but it won't compile. Struct: #define numThreads 1 struct Data { int threads; int delay; int messages; }; Call to method: HANDLE hThread; DWORD threadId; struct Data *tData; tData->threads = numThreads; tData->messages = 3; tData->delay = 1000; // Create child thread hThread = CreateThread( NULL, // lpThreadAttributes (default) 0, // dwStackSize (default) ThreadFunc, // lpStartAddress &tData, // lpParameter 0, // dwCreationFlags &threadId // lpThreadId (returned by function) ); My attempt: DWORD WINAPI ThreadFunc(LPVOID threadData) { struct Data tData = (struct Data)threadData; int msg; for(msg = 0; msg<5; msg++) { printf("Message %d from child\n", msg); } return 0; } Compiler error: error C2440: 'type cast' : cannot convert from 'LPVOID' to 'Data' As you can see I have implemented a way to loop through a number of messages already, I'm trying to make things slightly more advanced and add some further functionality.

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  • Strange casting problem with tm structure

    - by egiakoum1984
    I have the following casting problem when my data structure sSpecificData contains a field of type tm: typedef struct { unsigned char data[10000]; } sDataBuffer; typedef struct { int m_Id; sDataBuffer m_Data; } sData; typedef struct { int m_value1; int m_value2; tm m_Date; } sSpecificData; const int SPECIFIC_SVC_DATA_SIZE = sizeof(sSpecificData); typedef struct { int m_Id; sSpecificData m_Data; } sMyData; int main(void) { sData svc; sMyData* ptr1 = (sMyData*) &svc; sSpecificData* ptr2; ptr2 = (sSpecificData*) &svc.m_Data; ptr1->m_Data.m_value1 = 90; ptr1->m_Data.m_value2 = 80; cout << ptr1->m_Data.m_value1 << endl; cout << ptr1->m_Data.m_value2 << endl; cout << ptr2->m_value1 << endl; cout << ptr2->m_value2 << endl; return 0; } Without the field "tm m_Date;" as part of the sSpecificData, the output is correct: 90 80 90 80 With the field "tm m_Date;" as part of the sSpecificData, the output is wrong: 90 80 0 <-- ! 90 <-- ! Is there any idea why my example doesn't work when there is field of type tm as part of the sSpecificData? Thanks!

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  • JTree TreePath casting problem

    - by newbie123
    I got this casting problem java.lang.String cannot be cast to java.io.File, when I trying to do this TreePath p = new TreePath(new Object[] {"src","file","My Diary" }); This is my jtree file model class FileTreeModel implements TreeModel { private FileNode root; public FileTreeModel(String directory) { root = new FileNode(directory); } public Object getRoot() { return root; } public Object getChild(Object parent, int index) { FileNode parentNode = (FileNode) parent; return new FileNode(parentNode, parentNode.listFiles()[index].getName()); } public int getChildCount(Object parent) { FileNode parentNode = (FileNode) parent; if (parent == null || !parentNode.isDirectory() || parentNode.listFiles() == null) { return 0; } return parentNode.listFiles().length; } public boolean isLeaf(Object node) { return (getChildCount(node) == 0); } public int getIndexOfChild(Object parent, Object child) { FileNode parentNode = (FileNode) parent; FileNode childNode = (FileNode) child; return Arrays.asList(parentNode.list()).indexOf(childNode.getName()); } public void valueForPathChanged(TreePath path, Object newValue) { } public void addTreeModelListener(TreeModelListener l) { } public void removeTreeModelListener(TreeModelListener l) { } } class FileNode extends java.io.File { public FileNode(String directory) { super(directory); } public FileNode(FileNode parent, String child) { super(parent, child); } @Override public String toString() { return getName(); } }

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  • Scala implicit dynamic casting

    - by weakwire
    I whould like to create a scala Views helper for Android Using this combination of trait and class class ScalaView(view: View) { def onClick(action: View => Any) = view.setOnClickListener(new OnClickListener { def onClick(view: View) { action(view) } }) } trait ScalaViewTrait { implicit def view2ScalaView(view: View) = new ScalaView(view) } I'm able to write onClick() like so class MainActivity extends Activity with ScalaViewTrait { //.... val textView = new TextView(this) textView.onClick(v => v.asInstanceOf[TextView] setText ("asdas")) } My concern is that i want to avoid casting v to TextView v will always be TextView if is applied to a TextView LinearLayout if applied to LinearLayout and so on. Is there any way that v gets dynamic casted to whatever view is applied? Just started with Scala and i need your help with this. UPDATE With the help of generics the above get's like this class ScalaView[T](view: View) { def onClick(action: T => Any) = view.setOnClickListener(new OnClickListener { def onClick(view: View) { action(view.asInstanceOf[T]) } }) } trait ScalaViewTrait { implicit def view2ScalaView[T](view: View) = new ScalaView[T](view) } i can write onClick like this view2ScalaView[TextView](textView) .onClick(v => v.setText("asdas")) but is obvious that i don't have any help from explicit and i moved the problem instead or removing it

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  • [nHibernate] casting string to bool using nHibernate Criteria

    - by code-zoop
    I have an nHibernate query using Criteria, and I am trying to cast a string to bool in the query itself. I have done the same with casting a string to int, and that works well (the "DataField" property is "1" as a string): var result = Session .CreateCriteria<Car>() .Add(Restrictions.Eq((Projections.Cast(NHibernateUtil.Int32, Projections.Property("DataField"), 1)) .List<Car>(); tx.Commit(); But I am trying to do the same with bool, but I do not get the expected result: var result = Session .CreateCriteria<Car>() .Add(Restrictions.Eq((Projections.Cast(NHibernateUtil.bool, Projections.Property("DataField"), true)) .List<Car>(); tx.Commit(); "DataField" is the string "True", but the result in an empty list, where it should contain 100 elements with the "DataField" property string set to "True". I have tried with the string "true", and "1", but the result is still an empty List. [EDIT] As Commented below, I could check for the string "True" or "False", but I would say this is a more general question than just for the Boolean. Note that the idea is to have some sort of key value representation of the data, where the value can be different data types. I need the value table to contain all data, so storing the data as string seems like the cleanest solution! I have been able to use the method above to store both int and double as string, and to the cast in the query, but I have not succeeded using the same method for DateDime and Boolean. And for DateTime it is crucial to have the actual DateTime object. How can I make the cast from string to bool, and string to DateTime work in the queries? Thanks

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  • C# error casting from double to int32

    - by orfix
    using NUF = NUnit.Framework; [NUF.Test]public void DifferentCastingTest() { NUF.Assert.That((int)0.499999D, NUF.Is.EqualTo(0)); NUF.Assert.That((int)0.500000D, NUF.Is.EqualTo(0)); // !!! row 1 NUF.Assert.That((int)1.499999D, NUF.Is.EqualTo(1)); NUF.Assert.That((int)1.500000D, NUF.Is.EqualTo(1)); // !!! row 2 NUF.Assert.That(System.Convert.ToInt32(0.499999D), NUF.Is.EqualTo(0)); NUF.Assert.That(System.Convert.ToInt32(0.500000D), NUF.Is.EqualTo(0)); // !!! NUF.Assert.That(System.Convert.ToInt32(1.499999D), NUF.Is.EqualTo(1)); NUF.Assert.That(System.Convert.ToInt32(1.500000D), NUF.Is.EqualTo(2)); //!!! row 3 } The same double value (1.5D) is converted in different way by casting and Convert.ToInt32 (see row 2 and 3), and two double with same mantissa (0.5 and 1.5) is rounded in different mode (see row 1 and 2). Is it a bug?

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  • gcc, strict-aliasing, and casting through a union

    - by Joseph Quinsey
    About a year ago the following paragraph was added to the GCC Manual, version 4.3.4, regarding -fstrict-aliasing: Similarly, access by taking the address, casting the resulting pointer and dereferencing the result has undefined behavior [emphasis added], even if the cast uses a union type, e.g.: union a_union { int i; double d; }; int f() { double d = 3.0; return ((union a_union *)&d)->i; } Does anyone have an example to illustrate this undefined behavior? Note this question is not about what the C99 standard says, or does not say. It is about the actual functioning of gcc, and other existing compilers, today. My simple, naive, attempt fails. For example: #include <stdio.h> union a_union { int i; double d; }; int f1(void) { union a_union t; t.d = 3333333.0; return t.i; // gcc manual: 'type-punning is allowed, provided ...' } int f2(void) { double d = 3333333.0; return ((union a_union *)&d)->i; // gcc manual: 'undefined behavior' } int main(void) { printf("%d\n", f1()); printf("%d\n", f2()); return 0; } works fine, giving on CYGWIN: -2147483648 -2147483648 Also note that taking addresses is obviously wrong (or right, if you are trying to illustrate undefined behavior). For example, just as we know this is wrong: extern void foo(int *, double *); union a_union t; t.d = 3.0; foo(&t.i, &t.d); // UD behavior so is this wrong: extern void foo(int *, double *); double d = 3.0; foo(&((union a_union *)&d)->i, &d); // UD behavior For background discussion about this, see for example: http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1422.pdf http://gcc.gnu.org/ml/gcc/2010-01/msg00013.html http://davmac.wordpress.com/2010/02/26/c99-revisited/ http://cellperformance.beyond3d.com/articles/2006/06/understanding-strict-aliasing.html http://stackoverflow.com/questions/98650/what-is-the-strict-aliasing-rule http://stackoverflow.com/questions/2771023/c99-strict-aliasing-rules-in-c-gcc/2771041#2771041 The first link, draft minutes of an ISO meeting seven months ago, notes in section 4.16: Is there anybody that thinks the rules are clear enough? No one is really able to interpret tham.

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  • Cast from Void* to TYPE* using C++ style cast: static_cast or reinterpret_cast

    - by David Relihan
    So if your converting from Void* to Type* or from Type* to Void* should you use: void func(void *p) { Params *params = static_cast<Params*>(p); } or void func(void *p) { Params *params = reinterpret_cast<Params*>(p); } To me static_cast seems the more correct but I've seen both used for the same purpose. Also, does the direction of the conversion matter. i.e. should I still use static_cast for: _beginthread(func,0,static_cast<void*>(params) I have read the other questions on C++ style casting but I'm still not sure what the correct way is for this scenario (I think it is static_cast)

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  • Question about member function pointers in a heirarchy

    - by Jesse Beder
    I'm using a library that defines an interface: template<class desttype> void connect(desttype* pclass, void (desttype::*pmemfun)()); and I have a small heirarchy class base { void foo(); }; class derived: public base { ... }; In a member function of derived, I want to call connect(this, &derived::foo); but it seems that &derived::foo is actually a member function pointer of base; gcc spits out error: no matching function for call to ‘connect(derived* const&, void (base::* const&)())’ I can get around this by explicitly casting this to base *; but why can't the compiler match the call with desttype = base (since derived * can be implicitly cast to base *)? Also, why is &derived::foo not a member function pointer of derived?

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  • How can I type cast EventArgs to have a .point property in c#? [closed]

    - by Sean Smyth
    I'm working with a double click function in c#. the function takes an object and EventArgs as it's parameters: private void gvHL7_DoubleClick(object sender, EventArgs e){ . . . } However, I want to use the .Point property, and EventArgs doesn't have that property. I know that DevExpress.XtraGrid.Views.Grid.GridMenuEventArgs does, but it's saying that's an invalid casting. What type should I cast my EventArgs instance to if I wish to access the .Point property? Edit: The double click function I'm working with is provided by devexpress for their grids.

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  • Need help for this syntax: "#define LEDs (char *) 0x0003010"

    - by Noge
    I'm doing programming of a softcore processor, Nios II from Altera, below is the code in one of the tutorial, I manage to get the code working by testing it on the hardware (DE2 board), however, I could not understand the code. #define Switches (volatile char *) 0x0003000 #define LEDs (char *) 0x0003010 void main() { while (1) *LEDs = *Switches; } What I know about #define is that, it is either used to define a constant, or a macro, but why in the above code, there are casting like, (char *) 0x0003010, in #define? why the 2 constants, Switches and LEDs act like a variable instead of a constant? Thanks in advance !

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  • AS3 Accessing Variables of Parent Class From Child

    - by TheDarkIn1978
    i'm trying to assign a parent's variable from the parent's child //Parent public class Main extends Sprite { public var selectedSquare:Sprite; public function Main() { //inits and adds new Square child class to display list } ... ------- //Child public function dragSquare(evt:MouseEvent):void { Sprite(parent).selectedSquare = this; //evil doesn't work! parent.addChild(this); this.startDrag(); } i'm receiving this error, but i'm casting parent from displayObjectContainer to a Sprite so i have no idea why it's not working. 1119: Access of possibly undefined property selectedSquare through a reference with static type flash.display:Sprite.

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  • floating constants in C

    - by Daziplqa
    Hi floks, I have a question concerning floating constants in C. In Java, the default type of floating point constants in double, so the following will causes a compilation error in java: float f = 100.0; // we either need to uses type case operator or put f at the end of the number constant. This is because the default floating-point constants are of type double and casting from double to float without type cast operator is an error, so we need either add a type case operator or put f at the end of the number. So, Why in C this doesn't produce an error, Is it because the default floating-point constants are of type float, or because the compiler do an implicit down-cast conversion (that doesn't requires type case operator in C)????

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  • Avoid incompatible pointer warning when dealing with double-indirection

    - by fnawothnig
    Assuming this program: #include <stdio.h> #include <string.h> static void ring_pool_alloc(void **p, size_t n) { static unsigned char pool[256], i = 0; *p = &pool[i]; i += n; } int main(void) { char *str; ring_pool_alloc(&str, 7); strcpy(str, "foobar"); printf("%s\n", str); return 0; } ... is it possible to somehow avoid the GCC warning test.c:12: warning: passing argument 1 of ‘ring_pool_alloc’ from incompatible pointer type test.c:4: note: expected ‘void **’ but argument is of type ‘char **’ ... without casting to (void**) (or simply disabling the compatibility checks)? Because I would very much like to keep compatibility warnings regarding indirection-level...

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  • How to convert from integer to unsigned char in C, given integers larger than 256?

    - by Alf_InPogform
    As part of my CS course I've been given some functions to use. One of these functions takes a pointer to unsigned chars to write some data to a file (I have to use this function, so I can't just make my own purpose built function that works differently BTW). I need to write an array of integers whose values can be up to 4095 using this function (that only takes unsigned chars). However am I right in thinking that an unsigned char can only have a max value of 256 because it is 1 byte long? I therefore need to use 4 unsigned chars for every integer? But casting doesn't seem to work with larger values for the integer. Does anyone have any idea how best to convert an array of integers to unsigned chars?

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