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  • NSString inheritance

    - by Stef
    Hi, I'm doing an useless thing for my first step in Obj-C @interface String : NSString { int m_isnull; } - (id) init; - (int) isNull; @end @implementation String - (id) init { self = [super init]; m_isnull=1; return self; } - (int) isNull { return m_isnull; } @end test : String *a; a=@"ok"; Works fine, but just 2 little questions 1) When I'm compiling I have this warning warning: incompatible Objective-C types assigning 'struct NSString *', expected 'struct String *' I don't know how to avoid it !? 2) a=@"ok" is a fastest way to initialize a string, but when I'm debugging, I don't stop by at my init constructor why ?

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  • casting char* to char**

    - by blue_whale
    I am having a tough time understanding the following piece of code: int stride = 512; int max_len = 1024 * stride; char *addr = (char *)malloc(max_len); for (int i=stride; i<max_len; i += stride) *(char **)&addr[i-stride] = (char*)&addr[i]; *(char **)&addr[i-stride] = (char*)&addr[0]; Looking at the code it seems this is trying to create some kind of circular link list. But I have no clue what those casts are actually doing.

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  • semicolon in C++?

    - by SysAdmin
    Here is the question Is "missing semicolon" error really required? why not treat it as a warning? Why I am asking this stupid question? When I compile this code int f = 1 int h=2; the compiler intelligently tells me that where I am missing it. but to me its like - "If you know it, just treat it as if its there and go ahead. (Later I can fix the warning) int sdf = 1,df=2; sdf=1 df =2 even for this code it behaves the same. i.e even if multiple statements (without ;) are in the same line, the compiler knows. So, why not just remove this requirement? why not behave like python,vb etc

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  • Multiple WCF Services implementing same Service Contract interface

    - by andrewczwu
    Is it possible for multiple wcf services to implement the same service contract interface? What I want to do is allow for a test service to be interchangeable for the real service, and to specify which service to be used in the configuration file. For example: [ServiceContract] public interface IUselessService { [OperationContract] string GetData(int value); } Test implementation public class TestService : IUselessService { public string GetData(int value) { return "This is a test"; } } Real class public class RealService : IUselessService { public string GetData(int value) { return string.Format("You entered: {0}", value); } }

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  • string reverse without new array

    - by Codeguru
    hi can anybody tell me the error in this? #include<stdio.h> int main() { char a[]="abcdefgh"; int i=0; int n=strlen(a); char *first; char *second; char *c; *first=a[0]; *second=a[7]; for(i=0;i<=n/2;i++) { *c=*first; *first=*second; *second=*c; first++; second--; } for(i=0;i<=7;i++) { printf("%c",a[i]); } }

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  • Pass, edit and return variable in C

    - by Supertecnoboff
    I am new to C programming and recently I have been playing around with functions in C programming. But I have a simple problem: Basically I want to pass an integer to a function, have the function edit it and then pass back the integer to the main function. I am working on this but it isn't working..... Here is my code: int update_SEG_values(int DIGIT_1, int DIGIT_2) { // How many tens in the "TEMP_COUNT". DIGIT_2 = ((TEMP_COUNT) / 10); // How much is left for us to display. TEMP_COUNT = TEMP_COUNT - ((DIGIT_2) * 10); // How many ones. DIGIT_1 = ((TEMP_COUNT) / 1); return(DIGIT_1, DIGIT_2); } What am I doing wrong here?

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  • Python - multi-line array

    - by Ockonal
    Hi guys, in c++ I can wrote: int someArray[8][8]; for (int i=0; i < 7; i++) for (int j=0; j < 7; j++) someArray[i][j] = 0; And how can I initialize multi-line arrays in python? I tried: array = [[],[]] for i in xrange(8): for j in xrange(8): array[i][j] = 0

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  • Getting the fractional part of a float without using modf()

    - by knight666
    Hi, I'm developing for a platform without a math library, so I need to build my own tools. My current way of getting the fraction is to convert the float to fixed point (multiply with (float)0xFFFF, cast to int), get only the lower part (mask with 0xFFFF) and convert it back to a float again. However, the imprecision is killing me. I'm using my Frac() and InvFrac() functions to draw an anti-aliased line. Using modf I get a perfectly smooth line. With my own method pixels start jumping around due to precision loss. This is my code: const float fp_amount = (float)(0xFFFF); const float fp_amount_inv = 1.f / fp_amount; inline float Frac(float a_X) { return ((int)(a_X * fp_amount) & 0xFFFF) * fp_amount_inv; } inline float Frac(float a_X) { return (0xFFFF - (int)(a_X * fp_amount) & 0xFFFF) * fp_amount_inv; } Thanks in advance!

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  • Iterator to last element in std::list

    - by Dave18
    #include <list> using std::list; int main() { list <int> n; n.push_back(1); n.push_back(2); n.push_back(3); list <int>::iterator iter = n.begin(); std::advance(iter, n.size() - 1); //iter is set to last element } is there any other way to have an iter to the last element in list?

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  • Selecting distinct values from mysql with largest timestamp

    - by user987048
    I am building a mail system. The inbox is only supposed to grab the last message (one with the highest time value) of a concatenation of user and sender, where the user or sender is the user ID. Here is the table structure: CREATE TABLE IF NOT EXISTS `mail` ( `user` int(11) NOT NULL, `sender` int(11) NOT NULL, `body` text NOT NULL, `new` enum('0','1') NOT NULL default '1', `time` int(11) NOT NULL, KEY `user` (`user`) ) ENGINE=MyISAM DEFAULT CHARSET=utf8; So, with a table with the following data: user sender new time ***************************************** 1 0 0 5 1 0 0 6 2 1 0 7 1 0 1 8 1 2 0 9 1 0 1 11 1 2 1 12 I want to select the following: WHERE USER OR SENDER = X (in this case, 1) user sender new time ***************************************** 2 1 0 7 1 2 0 9 1 0 1 11 How would I go about doing something like this?

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  • variable scope in statement blocks

    - by fearofawhackplanet
    for (int i = 0; i < 10; i++) { Foo(); } int i = 10; // error, 'i' already exists ---------------------------------------- for (int i = 0; i < 10; i++) { Foo(); } i = 10; // error, 'i' doesn't exist By my understanding of scope, the first example should be fine. The fact neither of them are allowed seems even more odd. Surely 'i' is either in scope or not. Is there something non-obvious about scope I don't understand which means the compiler genuinely can't resolve this? Or is just a case of nanny-state compilerism?

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  • c++ - what is faster ?

    - by VaioIsBorn
    If we have the following 2 snippets of code in c++ that do the same task: int a, b=somenumber; while(b > 0) { a = b % 3; b /= 3; } or int b=somenumber; while(b > 0) { int a=b%3; b /= 3; } I don't know much about computer architecture/c++ design, but i think that the first code is faster because it declares the integer a at the beginning and just uses it in the while-loop, and in the second code the integer a is being declared everytime the while-loop starts over. Can some one help me with this, am i correct or what and why ?

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  • array of objects of a class

    - by anurag18294
    #include class test{ int a; char b; public: test() { cout<<"\n\nDefault constructor being called"; } test(int i,char j) { a=i; b=j; cout<<"\n\nConstructor with arguments called"; } }; int main() { test tarray[5]; test newobj(31,'z'); }; In the above code snippet can we intialize values to tarray[5].

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  • base pointer to derived class

    - by Jay
    Suppose there are Base class and Derived class. Base *A = new Base; Here A is a pointer point to Base class, and new constructs one that A points to. I also saw Base *B = new Derived; How to explain this? B is a pointer to Base Class, and a Derived class constructed and pointed by B? If there is a function derived from Base class, say, Virtual void f(), and it's been overridden in Derived class, then B->f() will invoke which version of the function? version in Base class, or version that overridden in Derived Class. What if there is a new function void g()in Derived, is B->g() going to invoke this function properly? One more is, is int *a = new double; or int *a = new int; legal?

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  • In a C++ template, is it allowed to return an object with specific type parameters?

    - by nieldw
    When I've got a template with certain type parameters, is it allowed for a function to return an object of this same template, but with different types? In other words, is the following allowed? template<class edgeDecor, class vertexDecor, bool dir> Graph<edgeDecor,int,dir> Graph<edgeDecor,vertexDecor,dir>::Dijkstra(vertex s, bool print = false) const { /* Construct new Graph with apropriate decorators */ Graph<edgeDecor,int,dir> span = new Graph<edgeDecor,int,dir>(); /* ... */ return span; }; If this is not allowed, how can I accomplish the same kind of thing?

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  • Is a Critical Section around an integer getter and setter redundant?

    - by Tim Gradwell
    Do critical sections inside trivial int accessors actually do anything useful? int GetFoo() { CriticalSection(crit_id); return foo; } void SetFoo(int value) { CriticalSection(crit_id); foo = value; } Is it possible for two threads to be attempting to read and write foo simultaneously? I'd have thought 'no' unless integers are written byte-at-a-time, in which case I can see the use. But I'd have though modern cpus would read/write integers in a single atomic action...

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  • Reference and Value confusion

    - by rgamber
    Hi I read this question on Stack overflow, and tried to do an example. I had the below code: public static void main(String[] args){ int i = 5; Integer I = new Integer(5); increasePrimitive(i); increaseObject(I); System.out.println(i); //Prints 5 - correct System.out.println(I); //Still prints 5 System.out.println(increaseObject2(I)); //Still prints 5 } public static void increasePrimitive(int n){ n++; } public static void increaseObject(Integer n){ n++; } public static int increaseObject2(Integer n){ return n++; } Does the increaseObject print 5 because the value of reference is changing inside that function? Am I right? I am confused why the increasedObject2 prints 5 and not 6. Can anyone please explain?

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  • how do i insert into two table all at once in a stored procedure?

    - by user996502
    Doing a project for school so any help would be great thank you! I have two tables how do i insert into two tables? so both tables are linked. First table called Customer with primary key called CID that auto increments CREATE TABLE [dbo].[Customer]( [CID] [int] IDENTITY(1,1) NOT NULL, [LastName] [varchar](255) NOT NULL, [FirstName] [varchar](255) NOT NULL, [MiddleName] [varchar](255) NULL, [EmailAddress] [varchar](255) NOT NULL, [PhoneNumber] [varchar](12) NOT NULL CONSTRAINT [PK__CInforma__C1F8DC5968DD69DC] PRIMARY KEY CLUSTERED ( And a second table called Employment that has a foreign key linked to the parent table CREATE TABLE [dbo].[Employment]( [EID] [int] IDENTITY(1,1) NOT NULL, [CID] [int] NOT NULL, [Employer] [varchar](255) NOT NULL, [Occupation] [varchar](255) NOT NULL, [Income] [varchar](25) NOT NULL, [WPhone] [varchar](12) NOT NULL, CONSTRAINT [PK__Employme__C190170BC7827524] PRIMARY KEY CLUSTERED (

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  • What is the problem with this code?

    - by eSKay
    #include<stdio.h> class A { public: int a;}; class B: public A { public: static int b; B(){ b++; printf("B:%d\n",b); } }; int main() { A* a1 = new B[100]; A* a2 = new B(); return 0; } Error: In function `main': undefined reference to `B::b' undefined reference to `B::b' undefined reference to `B::b' undefined reference to `B::b'

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  • Improve C function performance with cache locality?

    - by Christoper Hans
    I have to find a diagonal difference in a matrix represented as 2d array and the function prototype is int diagonal_diff(int x[512][512]) I have to use a 2d array, and the data is 512x512. This is tested on a SPARC machine: my current timing is 6ms but I need to be under 2ms. Sample data: [3][4][5][9] [2][8][9][4] [6][9][7][3] [5][8][8][2] The difference is: |4-2| + |5-6| + |9-5| + |9-9| + |4-8| + |3-8| = 2 + 1 + 4 + 0 + 4 + 5 = 16 In order to do that, I use the following algorithm: int i,j,result=0; for(i=0; i<4; i++) for(j=0; j<4; j++) result+=abs(array[i][j]-[j][i]); return result; But this algorithm keeps accessing the column, row, column, row, etc which make inefficient use of cache. Is there a way to improve my function?

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  • to store char* from function return value

    - by samprat
    Hi folks, I am trying to implement a function which reads from Serial Port ( Linux) and retuns char*. The function works fine but how would I store return value from function. example of function is char *ReadToSerialPort() { char *bufptr; char buffer[256]; // Input buffer/ / //char *bufptr; // Current char in buffer // int nbytes; // Number of bytes read // bufptr = buffer; while ((nbytes = read(fd, bufptr, buffer+sizeof(buffer)-bufptr -1 )) > 0) { bufptr += nbytes; // if (bufptr[-1] == '\n' || bufptr[-1] == '\r') /*if ( bufptr[sizeof(buffer) -1] == '*' && bufptr[0] == '$' ) { break; }*/ } // while ends if ( nbytes ) return bufptr; else return 0; *bufptr = '\0'; } // end ReadAdrPort //In main int main( int argc , char *argv[]) { char *letter; if(strcpy(letter, ReadToSerialPort()) >0 ) { printf("Response is %s\n",letter); } }

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  • What is the purpose of AnyVal?

    - by DaoWen
    I can't think of any situation where the type AnyVal would be useful, especially with the addition of the Numeric type for abstracting over Int, Long, etc. Are there any actual use cases for AnyVal, or is it just an artifact that makes the type hierarchy a bit prettier? Just to clarify, I know what AnyVal is, I just can't think of any time that I would actually need it in Scala. When would I ever need a type that encompassed Int, Character and Double? It seems like it's just there to make the type hierarchy prettier (i.e. it looks nicer to have AnyVal and AnyRef as siblings rather than having Int, Character, etc. inherit directly from Any).

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  • SQL Server 15MM rows, simple COUNT query. 15+ seconds?

    - by john
    We took over a website from another company after a client decided to switch. We have a table that grows by about 25k records a day, and is currently at 15MM records. The table looks something like: id (PK, int, not null) member_id (int, not null) another_id (int, not null) date (datetime, not null) SELECT COUNT(id) FROM tbl can take up to 15 seconds. A simple inner join on 'another_id' takes over 30 seconds. I can't imagine why this is taking so long. Any advice? SQL Server 2005 Express

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  • Extract inputs from a pointer to array of characters in C / C++

    - by user2066884
    I am writing a command line utility but I cannot find a way to store the commands and arguments. so far I have the following but I get a Segmentation fault: int main(void) { char *command; char *args[MAX_LINE/2 + 1]; int should_run = 1; do{ cout << "cmd> "; int counter = 0; while(cin >> command) { strcpy(args[counter],command); counter++; } cout << args[0] << "\n"; } }

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