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  • Hiding instantiated templates in shared library created with g++

    - by jchl
    I have a file that contains the following: #include <map> class A {}; void doSomething() { std::map<int, A> m; } When compiled into a shared library with g++, the library contains dynamic symbols for all the methods of std::map<int, A>. Since A is private to this file, there is no possibility that std::map will be instantiated in any other shared library with the same parameters, so I'd like to make the template instantiation hidden (for some of the reasons described in this document). I thought I should be able to do this by adding an explicit instantiation of the template class and marking it as hidden, like so: #include <map> class A {}; template class __attribute__((visibility ("hidden"))) std::map<int, A>; void doSomething() { std::map<int, A> m; } However, this has no effect: the symbols are still all exported. I even tried compiling with -fvisibility=hidden, but this also has no effect on the visibility of the methods of std::map<int, A> (although it does hide doSomething). The document I linked to above describes the use of export maps to restrict visibility, but that seems very tedious. Is there a way to do what I want in g++ (other than using export maps)? If so, what is it? If not, is there a good reason why these symbols must always be exported, or is this just a omission in g++?

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  • Writing a C++ wrapper for a C library

    - by stripes
    I have a legacy C library, written in an OO type form. Typical functions are like: LIB *lib_new(); void lib_free(LIB *lib); int lib_add_option(LIB *lib, int flags); void lib_change_name(LIB *lib, char *name); I'd like to use this library in my C++ program, so I'm thinking a C++ wrapper is required. The above would all seem to map to something like: class LIB { public: LIB(); ~LIB(); int add_option(int flags); void change_name(char *name); ... }; I've never written a C++ wrapper round C before, and can't find much advice about it. Is this a good/typical/sensible approach to creating a C++/C wrapper?

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  • C++ Static Array Initialization - Memory Issue

    - by donalmg
    Hi, I have a header file which contains a member variable declaration of a static char array: class ABC { public: static char newArray[4]; // other variables / functions private: void setArray(int i, char * ptr); } In the CPP file, I have the array initialized to NULL: char ABC::newArray[4] = {0}; In the ABC constructor, I need to overwrite this value with a value constructed at runtime, such as the encoding of an integer: ABC::ABC() { int i; //some int value defined at runtime memset(newArray, 0, 4); // not sure if this is necessary setArray(i,newArray); } ... void setArray(int i, char * value) { // encoding i to set value[0] ... value [3] } When I return from this function, and print the modified newArray value, it prints out many more characters than the 4 specified in the array declaration. Any ideas why this is the case. I just want to set the char array to 4 characters and nothing further. Thanks...

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  • New help with SQL Server select statement

    - by gio_333m
    I need help with select statement in SQL Server / T-SQL My table looks like this: Id (int) QuestionId (int) GenreId (int) I want to select random N rows from this table so that maximum number of same GenreId in the result set is less than X for all GenreId-s except one. For that one GenreId, I need row count with that GenreId to be equal to Y.

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  • how do I refactor this to make single function calls?

    - by stack.user.1
    I've been using this for a while updating mysql as needed. However I'm not too sure on the syntax..and need to migrate the sql to an array. Particulary the line database::query("CREATE TABLE $name($query)"); Does this translate to CREATE TABLE bookmark(name VARCHAR(64), url VARCHAR(256), tag VARCHAR(256), id INT) This is my ...guess. Is this correct? class table extends database { private function create($name, $query) { database::query("CREATE TABLE $name($query)"); } public function make($type) { switch ($type) { case "credentials": self::create('credentials', 'id INT NOT NULL AUTO_INCREMENT, flname VARCHAR(60), email VARCHAR(32), pass VARCHAR(40), PRIMARY KEY(id)'); break; case "booomark": self::create('boomark', 'name VARCHAR(64), url VARCHAR(256), tag VARCHAR(256), id INT'); break; case "tweet": self::create('tweet', 'time INT, fname VARCHAR(32), message VARCHAR(128), email VARCHAR(64)'); break; default: throw new Exception('Invalid Table Type'); } } }

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  • Pass reference to ArrayLists to a method.

    - by bhavna raghuvanshi
    here is the whole program: public class ListMerge { public static void main( String[] args) { Scanner input = new Scanner(System.in); System.out.println ("Input length of arraylist 1:"); int n = input.nextInt(); ArrayList x = new ArrayList(); ArrayList y = new ArrayList(); for (int i = 0; i < n; i++) { System.out.println ("Input x[ " + i +"] :" ); x.add(new Integer(i)); } System.out.println ("Input length of arraylist 2:"); int m = input.nextInt(); for (int i = 0; i < m; i++) { System.out.println ("Input y[ " + i +"] :" ); y.add(new Integer(i)); } } list int merge(ArrayList x, ArrayList y) { List all = new ArrayList(); all.addAll(x); all.addAll(y); System.out.println(all); return all; } } also tell me how do i call the function merge?

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  • Java: Incompatible Types

    - by user2922081
    import java.text.*; import java.util.*; public class Proj3 { public static void main(String[]args){ // DecimalFormat df = new DecimalFormat("#0.00”); Scanner s = new Scanner(System.in); int TotalHours = 0; int TotalGrade = 0; System.out.print("How many courses did you take? "); int Courses = Integer.parseInt(s.nextLine()); System.out.println(""); int CourseNumber = Courses - (Courses - 1); while (Courses > 0){ System.out.print("Course (" + CourseNumber +"): How many hours? "); int Hours = Integer.parseInt(s.nextLine()); TotalHours = TotalHours + Hours; System.out.print("Course (" + CourseNumber +"): Letter grade? "); char Grade = s.nextLine().charAt(0); if (Grade == 'A'){ TotalGrade = TotalGrade + (4 * Hours); } if (Grade == 'B'){ TotalGrade = TotalGrade + (3 * Hours); } if (Grade == 'C'){ TotalGrade = TotalGrade + (2 * Hours); } if (Grade == 'D'){ TotalGrade = TotalGrade + (1 * Hours); } Courses = Courses - 1; CourseNumber = CourseNumber + 1; } Double GPA = TotalGrade / TotalHours; System.out.println(df.format(GPA)); } } This is for an assignment and I don't know how to fix my problem. The Double GPA = TotalGrade / ToutalHours; line is coming up with the Incompatible Types error. Also I'm supposed to include the DecimalFormat df = new DecimalFormat("#0.00”);line at the beginning of the main but its not working. Anything is very helpful. Thanks

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  • Is it possible to embed C code in a C# project?

    - by Jonathan
    I know that it's possible to compile my C code into a dll, and then use P/Invoke to call that code. What I wondered if it was possible to have a chunk of C code embedded directly in my code, perhaps only available to one class... Something like this (non-working) example: public class MyClass { extern "C" { int do_something_in_c(int i) { return i*2; } } public int DoSomething(int value) { return do_something_in_c(value); } } I've been trying for a few hours using Visual Studio 2008, but I'm not getting anywhere, and I suspect that it isn't actually possible. Can anyone confirm or deny this? Thanks.

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  • Redundant naming in C/C++ typedefs/structs

    - by bloomy
    #include <stdio.h> #include <string.h> const int NAMELEN=30; const int MAXCLASSSIZE=10; typedef struct StudentRec { char lastname[NAMELEN]; char firstname[NAMELEN]; long int ID; int finalmark; }Student; I'm new to coding..and I have a question about why there is Student; after the bracket.. is it a format that we have to follow.

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  • I just don't get the C++ Pointer/Reference system.

    - by gnm
    I've never had problems with references as in Python (implicit) or PHP (explicit &). In PHP you write $p = &$myvar; and you have $p as a reference pointing to $myVar. So I know in C++ you can do this: void setToSomething( int& var ) { var = 123; } int myInt; setToSomething( myInt ); Myint is now 123, why? Doesn't & mean "memory address of" x in C++? What do I do then if var is only the adress to myInt and not a pointer? void setToSomething( int* var ) { var* = 123; } int myInt; int* myIntPtr = &myInt; setToSomething( myIntPtr ); Does the above work as expected? I don't understand the difference between * and & in C++ fully. They tell you & is used to get the adress of a variable, but why IN GODS NAME does that help you in functions etc. like in the first example?

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  • why does it use the movl instead of push ?!

    - by user554403
    hi all. pay attention to this code : #include <stdio.h> void a(int a, int b, int c) { char buffer1[5]; char buffer2[10]; } int main() { a(1,2,3); } after that : gcc -S a.c that command shows our source code in assembly. now we can see in the main function, we never use "push" command to push the arguments of the a function into the stack. and it used "movel" instead of that main: pushl %ebp movl %esp, %ebp andl $-16, %esp subl $16, %esp movl $3, 8(%esp) movl $2, 4(%esp) movl $1, (%esp) call a leave why does it happen? what's difference between them?

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  • Hibernate and mssql inner join rowcount

    - by ez2sarang
    I am struggling with Hibernate Criteria. My aim is to create the following request using Hibernate Criteria : select count(*) as y0_ from PInterface this_ inner join Product product2_ on this_.product_id=product2_.id where this_.product_interface_type_id=? Here is my code: @Entity @Table(name = "PInterface") public class PInterface { @Id @GeneratedValue @Column(name = "id", nullable = false, insertable = false, updatable = false) private int id; @Column(name = "product_id") private int productId; @Column(name = "product_interface_type_id") private int type; @ManyToOne(optional=false) @JoinColumn(name = "product_id", referencedColumnName = "id", insertable=false, updatable=false) private Product product; } @Entity @Table(name = "Product") public class Product { @Id @GeneratedValue @Column(name = "id", nullable = false, insertable = false, updatable = false) private int id; private String name; } //Criteria is : Object criteria = sessionFactory.getCurrentSession() .createCriteria(PInterface.class) .add(Restrictions.eq("type", 1)) .setProjection(Projections.rowCount()) .uniqueResult() ; However, the results ... select count(*) as y0_ from PInterface this_ where this_.product_interface_type_id=? Where Inner join? Thank you for help!

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  • Problem Initializing an Array Of Structs

    - by FallSe7en
    I am trying to initialize the following array of the following struct, but my code isn't compiling. Can anybody help me out? The struct/array: struct DiningCarSeat { int status; int order; int waiterNum; Lock customerLock; Condition customer; DiningCarSeat(seatNum) { char* tempLockName; sprintf(tempLockName, "diningCarSeatLock%d", seatNum); char* tempConditionName; sprintf(tempConditionName, "diningCarSeatCondition%d", seatNum); status = 0; order = 0; waiterNum = -1; customerLock = new Lock(tempLockName); customer = new Condition(tempConditionName); } } diningCarSeat[DINING_CAR_CAPACITY]; The relevant errors: ../threads/threadtest.cc: In constructor `DiningCarSeat::DiningCarSeat(int)': ../threads/threadtest.cc:58: error: no matching function for call to `Lock::Lock()' ../threads/synch.h:66: note: candidates are: Lock::Lock(const Lock&) ../threads/synch.h:68: note: Lock::Lock(char*) ../threads/threadtest.cc:58: error: no matching function for call to `Condition::Condition()' ../threads/synch.h:119: note: candidates are: Condition::Condition(const Condition&) ../threads/synch.h:121: note: Condition::Condition(char*) ../threads/threadtest.cc:63: error: expected primary-expression before '.' token ../threads/threadtest.cc:64: error: expected primary-expression before '.' token ../threads/threadtest.cc: At global scope: ../threads/threadtest.cc:69: error: no matching function for call to `DiningCarSeat::DiningCarSeat()' ../threads/threadtest.cc:51: note: candidates are: DiningCarSeat::DiningCarSeat(const DiningCarSeat&) ../threads/threadtest.cc:58: note: DiningCarSeat::DiningCarSeat(int) Thanks in advance!

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  • ActionScript Custom Class With Return Type?

    - by TheDarkIn1978
    i just know this is a dumb question, so excuse me in advance. i want to essentially classify a simple function in it's own .as file. the function compares integers. but i don't know how to call the class and receive a boolean return. here's my class package { public class CompareInts { public function CompareInts(small:int, big:int) { compare(small, big); } private function compare(small:int, big:int):Boolean { if (small < big) return true; else return false; } } } so now i'd like to write something like this: if (CompareInts(1, 5) == true). or output 'true' by writing trace(CompareInts(1, 5));

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  • Trying to get the associated value from an Enum at runtime in Java

    - by devoured elysium
    I want to accomplish something like the following (my interest is in the toInt() method). Is there any native way to accomplish this? If not, how can I get the integer associated with an enum value (like in C#) ? enum Rate { VeryBad(1), Bad(2), Average(3), Good(4), Excellent(5); private int rate; private Rate(int rate) { this.rate = rate; } public int toInt() { return rate; } } Thanks

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  • Multiply without multiplication, division and bitwise operators, and no loops. Recursion

    - by lxx22
    public class MultiplyViaRecursion{ public static void main(String[] args){ System.out.println("8 * 9 == " + multiply(8, 9)); System.out.println("6 * 0 == " + multiply(6, 0)); System.out.println("0 * 6 == " + multiply(0, 6)); System.out.println("7 * -6 == " + multiply(7, -6)); } public static int multiply(int x, int y){ int result = 0; if(y > 0) return result = (x + multiply(x, (y-1))); if(y == 0) return result; if(y < 0) return result = -multiply(x, -y); return result; } } My question is very simple and basic, why after each "if" the "return" still cannot pass the compilation, error shows missing return.

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  • Query to select from two different tables

    - by ryan
    I would like to select from two tables and display my result using this query: CREATE TABLE Buy_Table ( buy_id int identity primary key, user_id int, amount decimal (18,2) ); go INSERT INTO Buy_Table (user_id, amount) VALUES ('1', 10), ('1', 8), ('1', 20), ('3', 1), ('2', 2); go CREATE TABLE Sell_Table ( sell_id int identity primary key, user_id int, amount decimal (18,2) ); go INSERT INTO Sell_Table (user_id, amount) VALUES ('1', 10), ('1', 8), ('1', 20), ('3', 3), ('2', 3); go select [user_id], 'Buy' as [Type], buy_id as [ID], amount from Buy_Table union all select [user_id], 'Sell', sell_id, amount from Sell_Table order by [user_id], [ID], [Type] However the above query will return each row of the user_id like this I want to display my result to something like this in a grid: Can this be done in query itself rather manipulating the grid? Thx

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  • if `int != 1` or `int == 0`?

    - by Emil
    Hey. I was coding here the other day, writing a couple of if statements with ints that are always either zero or one (~bools), and I asked myself: Should I use if (int == 1) or if (int != 0) ? Is there any difference at all? Please, don't answer with stuff regarding the int may being more/less than 1/0, that's not what I want to know.

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  • How to make a SUM of Dictionary Value nested into a list with LINQ ?

    - by user551108
    Hi All, I have a product object declared as : Product { int ProductID; string ProductName; int ProductTypeID; string ProductTypeName; int UnitsSold Dictionary <string, int> UnitsSoldByYear; } I want to make a sum on UnitsSold and UnitsSoldByYear properties with a Linq query but I didn't know how to make this kind of sum on a dictionary ! Here is my begining linq query code : var ProductTypeSum = from i in ProductsList group i by new { i.ProductTypeID, i.ProductTypeName} into pt select new { ProductTypeID= pt.Key.ProductTypeID, ProductTypeName= pt.Key.ProductTypeName, UnitsSoldSum= pt.Sum(i => i.UnitsSold), // How to make a Dictionary sum here } Thank you for your help !

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  • Remove duplicates in a linked list before adding - C

    - by DesperateCoders
    Hi, My question is about removing duplicates from a linked list. But i want to do it before adding to linked list. struct myStr{int number; mystr *next;} void append(mystr **q,int item) { myStr *temp; temp = *q; myStr *newone; if(*q==NULL)// There should be control of previous elements. Call of keysearch function. { temp = (myStr *)malloc(sizeof(myStr)); temp->number =size; temp->next=NULL; *q=temp; } else //And also here { temp = *q; while(temp->next !=NULL) { temp=temp->next; } newone = (myStr *)malloc(sizeof(myStr)); newone->count = size; newone->next=NULL; temp->next=newone; } } int keysearch (myStr *p) { struct myStr *temp = p; int found = 0; int key= p->number; while (temp->number != NULL) { if(temp->number == key) { found = 1; } temp = temp->next; } return found; } My problem is in keySearch. I don't know what is wrong? Or is there another way for doing this.

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  • Java loop and increment problem

    - by user552961
    Can any one tell me what is the problem in my program? String a[],b[]; int c[] = new int[b.length]; for (int j = 0; j < a.length; j++) { for (int k = 0; k < b.length; k++) { if (b[k].equals(a[j])) { c[k]++; } else { c[k] = 0; } } } I have thousands of words stored in a HashMap. Now I want to check in every file that how many time one word occurred from allWords. Can you point out mistake in my program or give me your idea that how I can do it?

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