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  • OpenCV multiply scalar and a Matrix

    - by jarjarbinks
    Hi, I am trying to find the easiest way to add, subtract a scalar value with a opencv 2.0 cv::Mat class. Most of the existing function allows only matrix-matrix and matrix-scalar operations. I am looking for a scalar-matrix operations. I am doing it currently by creating a temporary matrix with the same scalar value and doing required arithmetic operation. Example below.. Mat M(Size(100,100), CV_8U); Mat temp = Mat::ones(100, 100, CV_8U)*255; M = temp-M; But I think there should be better/easier ways to do it. Any suggestions ?

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  • Multiplying char and int together in C

    - by teehoo
    Today I found the following: #include <stdio.h> int main(){ char x = 255; int z = ((int)x)*2; printf("%d\n", z); //prints -2 return 0; } So basically I'm getting an overflow because the size limit is determined by the operands on the right side of the = sign?? Why doesn't casting it to int before multiplying work? In this case I'm using a char and int, but if I use "long" and "long long int" (c99), then I get similar behaviour. Is it generally advised against doing arithmetic with operands of different sizes?

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  • Is there a calculator with LaTeX-syntax?

    - by Jørgen Fogh
    When I write math in LaTeX I often need to perform simple arithmetic on numbers in my LaTeX source, like 515.1544 + 454 = ???. I usually copy-paste the LaTeX code into Google to get the result, but I still have to manually change the syntax, e.g. \frac{154,7}{25} - (289 - \frac{1337}{42}) must be changed to 154,7/25 - (289 - 1337/42) It seems trivial to write a program to do this for the most commonly used operations. Is there a calculator which understand this syntax? EDIT: I know that doing this perfectly is impossible (because of the halting problem). Doing it for the simple cases I need is trivial. \frac, \cdot, \sqrt and a few other tags would do the trick. The program could just return an error for cases it does not understand.

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  • Fastest way to calculate an X-bit bitmask?

    - by Virtlink
    I have been trying to solve this problem for a while, but couldn't with just integer arithmetic and bitwise operators. However, I think its possible and it should be fairly easy. What am I missing? The problem: to get an integer value of arbitrary length (this is not relevant to the problem) with it's X least significant bits sets to 1 and the rest to 0. For example, given the number 31, I need to get an integer value which equals 0x7FFFFFFF (31 least significant bits are 1 and the rest zeros). Of course, using a loop OR-ing a shifted 1 to an integer X times will do the job. But that's not the solution I'm looking for. It should be more in the direction of (X << Y - 1), thus using no loops.

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  • Making sure unsigned int/long always execute in checked context in C#

    - by theburningmonk
    Has anyone found it strange that the default context for uint and ulong is unchecked rather than checked considering that they are meant to represent values that can never be negative? So if some code is trying to violate that constraint it seems to me the natural and preferred behaviour would be to throw an exception rather than returning the max value instead (which can easily leave important pieces of data in an invalid state and impossible to revert..). Is there an existing attribute which can be applied to either class/assembly so that it always performs arithmetic operations in a checked context? I was thinking of writing one myself (as an aspect using PostSharp) but would be great if there's one already. Many thanks,

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  • SQL Convert Nvarchar(255) to DateTime problem

    - by steven
    Hi, I'm using SQL server 2008. I have 2 Tables: Table 1 and Table 2. Table 1 has 1 column called: OldDate which is nvarchar(255), null Table 2 has 1 column called: NewDate which is datetime, not null Example data in Table 1: 26/07/03 NULL NULL 23/07/2003 7/26/2003 NULL 28/07/03 When i try CAST(OldDate as datetime) I get this error: Arithmetic overflow error converting expression to data type datetime. I need to insert OldDate into NewDate with no errors. I can't skip some rows. Anyhelp would be appreciated.

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  • Is it possible to pass arithmatic operators to a method in java?

    - by user349611
    Right now I'm going to have to write a method that looks like this: public String Calculate(String Operator, Double Operand1, Double Operand2) { if (Operator.equals("+")) { return String.valueOf(Operand1 + Operand2); } else if (Operator.equals("-")) { return String.valueOf(Operand1 - Operand2); } else if (Operator.equals("*")) { return String.valueOf(Operand1 * Operand2); } else { return "error..."; } } It would be nice if I could write the code more like this: public String Calculate(String Operator, Double Operand1, Double Operand2) { return String.valueOf(Operand1 Operator Operand2); } So Operator would replace the Arithmetic Operators (+, -, *, /...) Does anyone know if something like this is possible in java?

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  • how to return C++ pointer in objective-C++

    - by John Smith
    I have the following objective-C++ header with the simple method to return this pointer. @interface MyObj { MyCPPObj * cpp; } -(MyCPPObj *) getObj; I have created the simple method @implementation MyObj -(MyCPPObj *) getObj { return cpp; } Everything seems to work until I actually try to use the object in another file newObj = [createdMyObj getObj]; It complains: error: cannot convert 'objc_object*' to 'MyCPPObje *' in initialization. It seems that the method is return an objective-c object, but I specifically requested a C++ pointer. How can I fix that?

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  • Use of double pointer in linux kernel Hash list implementation

    - by bala1486
    Hi, I am trying to understand Linux Kernel implementation of linked list and hash table. A link to the implementation is here. I understood the linked list implementation. But i am little confused of why double pointers is being used in hlist (**pprev). Link for hlist is here. I understand that hlist is used in implementation of hash table since head of the list requires only one pointer and it saves space. Why cant it be done using single pointer (just *prev like the linked list)? Please help me.

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  • in free(): error: junk pointer, too high to make sense Segmentation fault: 11 (core dumped) gprof

    - by Mayank
    I am trying to profile my application. For this I compiled my code with -pg and -lc_p option, it compiled successfully During run time I am getting the following error. in free(): error: junk pointer, too high to make sense Segmentation fault: 11 (core dumped) Doing GDB gives error as. (gdb) b main Breakpoint 1 at 0x5124d4: (gdb) r warning: Unable to get location for thread creation breakpoint: generic error [New LWP 100085] cacheIp in free(): error: junk pointer, too high to make sense Program received signal SIGSEGV, Segmentation fault. [Switching to LWP 100085] 0x00000000006c3a1f in pthread_sigmask () My application is multi threaded and is a combination of C and C++ code. uname -a FreeBSD 6.3-RELEASE FreeBSD 6.3-RELEASE #0: Wed Jan 16 01:43:02 UTC 2008 [email protected]:/usr/obj/usr/src/sys/SMP amd64 Why is the code crashing. Am I missing something.

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  • Function Pointer from base class

    - by camelord
    Hi there, i need a Function Pointer from a base class. Here is the code: class CActionObjectBase { ... void AddResultStateErrorMessage( const char* pcMessage , ULONG iResultStateCode); ... } CActionObjectCalibration( ): CActionObjectBase() { ... m_Calibration = new CCalibration(&CActionObjectBase::AddResultStateErrorMessage); } class CCalibration { ... CCalibration(void (CActionObjectBase::* AddErrorMessage)(const char*, ULONG )); ... void (CActionObjectBase::* m_AddErrorMessage)(const char*, ULONG ); } Inside CCalibration in a Function occurs the Error. I try to call the Function Pointer like this: if(m_AddErrorMessage) { ... m_AddErrorMessage("bla bla", RSC_FILE_ERROR); } The Problem is, that I cannot compile. The Error Message says something like: error C2064: Expression is no Function, that takes two Arguments. What is wrong? regards camelord

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  • C: Cannot declare pointer inside if statement

    - by echedey lorenzo
    Hi, I have a pointer which points to a function. I would like to: if (mode == 0) { const unsigned char *packet = read_serial_packet(src, &len); } else { const unsigned char *packet = read_network_packet(fd, &len); } But I cannot do it because my compiler complains when I first use the pointer later in the code. error: 'packet' undeclared (first use in this function) This is strange. It worked without the if statement, but now I need my program to be able to get data from different sources. Isn't it possible to do this? I think so. If it isn't, is there any other simple way to get what I am trying? Thanks a lot.

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  • Get pointer to member function from within member function in C++

    - by Eli
    Currently in the program I am attempting to write I need to be able to get a pointer to a member function within a member function of the same class. The pointer needs to be passed to a function as a void (*)(). Example: //CallFunc takes a void (*)() argument class testClass { public: void aFunc2; void aFunc1; } void testClass:aFunc2(){ callFunc(this.*aFunc1); // How should this be done? } void testClass:aFunc1(){ int someVariable = 1; } I'm trying to do this in GCC 4.0.1. Also, the member function being called can't be static because it references non-static variables in the class that it is part of.

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  • C 64-bit Pointer Alignment

    - by DuneBug
    Are pointers on a 64-bit system still 4 byte aligned (similar to a double on a 32 bit system)? Or are they note 8 byte aligned? For example, on a 64-bit system how big is the following data structure: struct a { void* ptr; char myChar; } Would the pointer by 8 byte aligned, causing 7 bytes of padding for the character (total = 8 + 8 = 16)? Or would the pointer be 4 byte aligned (4 bytes + 4 bytes) causing 3 bytes of padding (total = 4 + 4 + 4 = 12)? Thanks, Ryan

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  • declaring a 2D array of pointer objects

    - by Tyler Stennette
    I'm having a tough time figuring out how to instantiate a 2D array of pointer objects. Here is how I'm doing it: Pieces* chessBoard[9][9]; When I want to set it to an actual object pointer, I'm doing the following: chessBoard[1][1] = new Rook(p1Rook); Rook is a class that inherits attributes from the Pieces class and p1Rook is a char variable set to 'R'. This class also implements virtual functions (not pure virtual) from Pieces such as move() or getPiece() that are unique to the particular chess piece. However, when I compile my program, I get the following error: ChessBoard.cpp:69: error: expected type-specifier before ‘Rook’ ChessBoard.cpp:69: error: cannot convert ‘int*’ to ‘Pieces*’ in assignment Can someone please explain what I should change to get rid of this rather annoying persistent error? I would appreciate it.

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  • Inline assembler get address of pointer Visual Studio

    - by Joe
    I have a function in VS where I pass a pointer to the function. I then want to store the pointer in a register to further manipulate. How do you do that? I have tried void f(*p) { __asm mov eax, p // try one FAIL __asm mov eax, [p] // try two FAIL __asm mov eax, &p // try three FAIL } Both 1 and 2 are converted to the same code and load the value pointed to. I just want the address. Oddly, option 1 works just fine with integers. void f() { int i = 5; __asm mov eax, i // SUCCESS? }

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  • Inline assembler getaddress of pointer Visual Studio

    - by Joe
    I have a function in VS where I pass a pointer to the function. I then want to store the pointer in a register to further manipulate. How do you do that? I have tried void f(*p) { __asm mov eax, p // try one FAIL __asm mov eax, [p] // try two FAIL __asm mov eax, &p // try three FAIL } Both 1 and 2 are converted to the same code and load the value pointed to. I just want the address. Oddly, option 1 works just fine with integers. void f() { int i = 5; __asm mov eax, i // SUCCESS? }

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  • How to I reference a pointer from a different class

    - by Justagruvn
    Hey team of awesomeness!, (Iphone Objective-C question) First off, I despise singletons with a passion. Though I should probably be trying to use one, I just dont want to. I want to create a data class (that is instantiated only once by a view controller on loading), and then using a different class, message the crap out of that data instance until it is brimming with so much data, it smiles. So, how do i do that? I made a pointer to the instance of the data class when I instantiated it. I'm now over in a separate view controller, action occurs, and I want to update the initial data object. I think I need to reference that object by way of pointer, but I have no idea how to do that. yes I've set properties and getters and setters, which seem to work, but only in the initial view controller class. Peace Love applesauce.

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  • C++ Pointer Issue

    - by Winder
    _stuckVertices is an array of pointers and I would like to update one index of that array without using _stuckVertices[ (row * _cols) + column ] 3 times. The reason it is an array of pointers is because the vast majority of the time the pointer will be NULL. The following code works but I need to dereference a each time I use it: void Cloth::stickPoint(int column, int row) { Anchor **a = &_stuckVertices[ (row * _cols) + column ]; if (!*a) *a = new Anchor(this, column, row); (*a)->stick(); } I originally had it written like this, but the _stuckVertices pointer doesn't get updated: void Cloth::stickPoint(int column, int row) { Anchor *a = _stuckVertices[ (row * _cols) + column ]; if (!a) a = new Anchor(this, column, row); a->stick(); } Is there a way to write Anchor *a = _stuckVertices[ index ] so that a is like an alias into the array that I can update, or is something like the first piece of code how I should do this? Thanks

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